Rutherford performed his most famous work after receiving the Nobel prize in 1908. Along with Hans Geiger and Ernest Marsden in 1909, he carried out the Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil. Rutherford was inspired to ask Geiger and Marsden in this experiment to look for alpha particles with very high deflection angles, of a type not expected from any theory of matter at that time. Such deflections, though rare, were found, and proved to be a smooth but high-order function of the deflection angle. It was Rutherford's interpretation of this data that led him to formulate the Rutherford model of the atom in 1911that a very small charged nucleus, containing much of the atom's mass, was orbited by low-mass electrons.
Gold foil experiment
Ernest Rutherford
Ernest Rutherford | Gold foil experiment
The Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil. He carried out the Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil. T he Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil. He demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil.
who was lise meitner?
user
She was an Austrian-Swedish physicist.
assistant
in which country did she live in her early days?
user
In the Leopoldstadt district of Vienna
assistant
any particular educational institution that she attended as a student?
user
University of Vienna
assistant
why did she have to flee from germany?
user
Because she lost her Austrian citizenship.
assistant
why?
user
Sorry. I cannot find the answer based on the context.
assistant
can you mention any of her contributions?
user
She completed the work on beta ray spectrum that she had begun with Hahn and Baeyer, and also her own study of the uranium decay chain.
assistant
could you please elaborate the last reaction?
user
It refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations - a.k.a. "radioactive cascade".
assistant
can you mention any health hazard caused by this decay?
user
The dangers are not immediately recognized.
assistant
who discovered this decay?
user
Ernest Rutherford, Frederick Soddy
assistant
who was the former?
user
He was  a New Zealand–born British physicist who came to be known as the father of nuclear physics.
assistant
what was his fabled experiment with gold ?
user
The only alternative to neutrons was the existence of "nuclear electrons" which would counteract some of the proton charges in the nucleus, since by then it was known that nuclei had about twice the mass that could be accounted for if they were simply assembled from hydrogen nuclei (protons). But how these nuclear electrons could be trapped in the nucleus, was a mystery.
Ernest Rutherford | Gold foil experiment
Thus, confirming and extending the work of Wilhelm Wien who in 1898 discovered the proton in streams of ionized gas, Rutherford postulated the hydrogen nucleus to be a new particle in 1920, which he dubbed the "proton". In 1921, while working with Niels Bohr (who postulated that electrons moved in specific orbits), Rutherford theorized about the existence of neutrons, (which he had christened in his 1920 Bakerian Lecture), which could somehow compensate for the repelling effect of the positive charges of protons by causing an attractive nuclear force and thus keep the nuclei from flying apart from the repulsion between protons.
Ernest Rutherford | Gold foil experiment
In 1919–1920, Rutherford found that nitrogen and other light elements ejected a proton, which he called a "hydrogen atom", when hit with α (alpha) particles. This result showed Rutherford that hydrogen nuclei were a part of nitrogen nuclei (and by inference, probably other nuclei as well). Such a construction had been suspected for many years on the basis of atomic weights which were whole numbers of that of hydrogen; see Prout's hypothesis. Hydrogen was known to be the lightest element, and its nuclei presumably the lightest nuclei. Now, because of all these considerations, Rutherford decided that a hydrogen nucleus was possibly a fundamental building block of all nuclei, and also possibly a new fundamental particle as well, since nothing was known from the nucleus that was lighter.
Ernest Rutherford | Gold foil experiment
The Geiger–Marsden experiments (also called the Rutherford gold foil experiment) were a landmark series of experiments by which scientists discovered that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. They deduced this after measuring how an alpha particle beam is scattered when it strikes a thin metal foil. The experiments were performed between 1908 and 1913 by Hans Geiger and Ernest Marsden under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester.
Geiger–Marsden experiment | Introduction
Rutherford performed his most famous work after receiving the Nobel prize in 1908. Along with Hans Geiger and Ernest Marsden in 1909, he carried out the Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil. Rutherford was inspired to ask Geiger and Marsden in this experiment to look for alpha particles with very high deflection angles, of a type not expected from any theory of matter at that time. Such deflections, though rare, were found, and proved to be a smooth but high-order function of the deflection angle. It was Rutherford's interpretation of this data that led him to formulate the Rutherford model of the atom in 1911that a very small charged nucleus, containing much of the atom's mass, was orbited by low-mass electrons.
Ernest Rutherford | Gold foil experiment
At the University of Manchester between 1908 and 1913, Rutherford directed Hans Geiger and Ernest Marsden in a series of experiments to determine what happens when alpha particles scatter from metal foil. Now called the Rutherford gold foil experiment, or the Geiger–Marsden experiment, these measurements made the extraordinary discovery that alpha particles would occasionally scatter to a high angle when passing through a thin gold foil. The scattering indicated that the alpha particles were deflected by a small, but dense, component of atoms. Based on these measurements, by 1911 it was apparent to Rutherford that the atom consisted of a small massive nucleus with positive charge surrounded by a much larger cloud of negatively charged electrons.
Discovery of the neutron | The gold foil experiment and the discovery of the atomic nucleus
They observed that a very small percentage of particles were deflected through angles much larger than 90 degrees. The gold foil experiment showed large deflections for a small fraction of incident particles. Rutherford realized that, because some of the alpha particles were deflected or reflected, the atom had a concentrated centre of positive charge and of relatively large mass - Rutherford later termed this positive center the "atomic nucleus". The alpha particles had either hit the positive centre directly or passed by it close enough to be affected by its positive charge. Since many other particles passed through the gold foil, the positive centre would have to be a relatively small size compared to the rest of the atom - meaning that the atom is mostly open space.
History of chemistry | Ernest Rutherford
He also coined the terms alpha, beta and gamma rays, he converted nitrogen into oxygen, and most importantly he supervised the students who did the Geiger–Marsden experiment (gold foil experiment) which showed that the 'plum pudding model' of the atom was wrong. In the plum pudding model, proposed by J. J. Thomson in 1904, the atom is composed of electrons surrounded by a 'cloud' of positive charge to balance the electrons' negative charge. To Rutherford, the gold foil experiment implied that the positive charge was confined to a very small nucleus leading first to the Rutherford model, and eventually to the Bohr model of the atom, where the positive nucleus is surrounded by the negative electrons.
Nuclear chemistry | History
The concentrated atomic mass was required to provide the observed deflection of the alpha particles, and Rutherford developed a mathematical model that accounted for the scattering. The Rutherford model was very influential, motivating the Bohr model for electrons orbiting the nucleus in 1913 and eventually leading to quantum mechanics by the mid-1920s.
Discovery of the neutron | The gold foil experiment and the discovery of the atomic nucleus
Rutherford backscattering spectrometry is named after Lord Rutherford, a physicist sometimes referred to as the father of nuclear physics. Rutherford supervised a series of experiments carried out by Hans Geiger and Ernest Marsden between 1909 and 1914 studying the scattering of alpha particles through metal foils. While attempting to eliminate "stray particles" they believed to be caused by an imperfection in their alpha source, Rutherford suggested that Marsden attempt to measure backscattering from a gold foil sample. According to the then-dominant plum-pudding model of the atom, in which small negative electrons were spread through a diffuse positive region, backscattering of the high-energy positive alpha particles should have been nonexistent.
Rutherford backscattering spectrometry | The Geiger–Marsden experiment
Otto Baumbach (1882-1966) was the glassblower who built part of the apparatus used by Ernest Rutherford and colleagues in the famous Gold foil experiment. In fact, this experiment has been referred to as the Rutherford-Royds-Baumbach experiment: It was Baumbach's ability to blow, "fine tubes very uniform in thickness." which led to him being key to Rutherford's work. In fact, such was Baumbach's skill that he was involved in many important experiments and acknowledged on some of the associated publications.
Otto Baumbach | Introduction
Born in Manchester, the son of Thomas Marsden and Phoebe Holden, Marsden lived in Rishton and attended Queen Elizabeth's Grammar School, Blackburn, where an inter-house trophy rewarding academic excellence ('The Marsden Merit Trophy') bears his name. In 1909, as a 20-year-old student at the University of Manchester, he met and began work under Ernest Rutherford. While still an undergraduate he conducted the famous Geiger–Marsden experiment, also called the gold foil experiment, together with Hans Geiger under Rutherford's supervision. This experiment led to Rutherford's new theory for the structure of the atom, with a centralised concentration of mass and positive charge surrounded by empty space and a sea of orbiting negatively charged electrons.
Ernest Marsden | Education
Rutherford overturned Thomson's model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny and heavy nucleus. Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure. If Thomson was correct, the beam would go straight through the gold foil. Most of the beams went through the foil, but a few were deflected. Rutherford presented his own physical model for subatomic structure, as an interpretation for the unexpected experimental results. In it, the atom is made up of a central charge (this is the modern atomic nucleus, though Rutherford did not use the term "nucleus" in his paper) surrounded by a cloud of (presumably) orbiting electrons.
Rutherford model | Experimental basis for the model
In 1906 at the University of Manchester, Rutherford oversaw an experiment conducted by his students Hans Geiger (known for the Geiger counter) and Ernest Marsden. In the Geiger–Marsden experiment, a beam of alpha particles, generated by the radioactive decay of radon, was directed normally onto a sheet of very thin gold foil in an evacuated chamber. Under the prevailing plum pudding model, the alpha particles should all have passed through the foil and hit the detector screen, or have been deflected by, at most, a few degrees. However, the actual results surprised Rutherford. Although many of the alpha particles did pass through as expected, many others were deflected at small angles while others were reflected back to the alpha source.
History of chemistry | Ernest Rutherford
In 1906, Ernest Rutherford published "Radiation of the α Particle from Radium in passing through matter." Hans Geiger expanded on this work in a communication to the Royal Society with experiments he and Rutherford had done, passing alpha particles through air, aluminum foil and gold leaf. More work was published in 1909 by Geiger and Ernest Marsden, and further greatly expanded work was published in 1910 by Geiger. In 1911–1912 Rutherford went before the Royal Society to explain the experiments and propound the new theory of the atomic nucleus as we now understand it. The key experiment behind this announcement was performed in 1910, at the University of Manchester: Ernest Rutherford's team performed a remarkable experiment in which Geiger and Marsden under Rutherford's supervision fired alpha particles (helium nuclei) at a thin film of gold foil.
Nuclear physics | Rutherford's team discovers the nucleus
Geiger and Marsden reused the above apparatus to measure how the scattering pattern varied with the square of the nuclear charge (i.e. if "s ∝ Q"). Geiger and Marsden didn't know what the positive charge of the nucleus of their metals were (they had only just discovered the nucleus existed at all), but they assumed it was proportional to the atomic weight, so they tested whether the scattering was proportional to the atomic weight squared. Geiger and Marsden covered the holes of the disc with foils of gold, tin, silver, copper, and aluminum. They measured each foil's stopping power by equating it to an equivalent thickness of air.
Geiger–Marsden experiment | The 1913 experiment
Rutherford later described this as "almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back to hit you". The apparatus used in the experiment was an early version of what was to become the Geiger counter.
Ernest Marsden | Education
Most flew straight through the foil with negligible deflection. To explain this bizarre result, Rutherford imagined that the positive charge of the atom was concentrated in a tiny nucleus at its center, which in turn meant that most of the atom's volume was empty space.
Geiger–Marsden experiment | The outcome of the experiments
Initial experiments were carried out in September 1954. No alpha decay was seen from mendelevium atoms; thus, Ghiorso suggested that the mendelevium had all decayed by electron capture to fermium and that the experiment should be repeated to search instead for spontaneous fission events. The repetition of the experiment happened in February 1955. On the day of discovery, 19 February, alpha irradiation of the einsteinium target occurred in three three-hour sessions. The cyclotron was in the University of California campus, while the Radiation Laboratory was on the next hill. To deal with this situation, a complex procedure was used: Ghiorso took the catcher foils (there were three targets and three foils) from the cyclotron to Harvey, who would use aqua regia to dissolve it and pass it through an anion-exchange resin column to separate out the transuranium elements from the gold and other products.
Mendelevium | Discovery
He found that a sample of this radioactive material of any size invariably took the same amount of time for half the sample to decay – its "half-life" (11½ minutes in this case). From 1900 to 1903, he was joined at McGill by the young chemist Frederick Soddy (Nobel Prize in Chemistry, 1921) for whom he set the problem of identifying the thorium emanations. Once he had eliminated all the normal chemical reactions, Soddy suggested that it must be one of the inert gases, which they named thoron (later found to be an isotope of radon). They also found another type of thorium they called Thorium X, and kept on finding traces of helium.
Ernest Rutherford | Scientific research
Rutherford moved in 1907 to the Victoria University of Manchester (today University of Manchester) in the UK, where he and Thomas Royds proved that alpha radiation is helium nuclei. Rutherford performed his most famous work after he became a Nobel laureate. In 1911, although he could not prove that it was positive or negative, he theorized that atoms have their charge concentrated in a very small nucleus, and thereby pioneered the Rutherford model of the atom, through his discovery and interpretation of Rutherford scattering by the gold foil experiment of Hans Geiger and Ernest Marsden. He performed the first artificially induced nuclear reaction in 1917 in experiments where nitrogen nuclei were bombarded with alpha particles.
Ernest Rutherford | Introduction
In 1934, working at the Cavendish Laboratory in Cambridge, England he and James Chadwick, through what they called the nuclear photo-electric effect, established that the neutron has a great enough mass over the proton to decay. He moved to the University of Illinois in 1938. In the 1940s with his wife Gertrude Scharff-Goldhaber he established that beta particles are identical to electrons. He joined Brookhaven National Laboratory in 1950. With Edward Teller he proposed that the so-called "giant-dipole nuclear resonance" was due to the neutrons in a nucleus vibrating as a group against the protons as a group (Goldhaber-Teller model).
Maurice Goldhaber | Career
After Rutherford's discovery, scientists started to realise that the atom is not ultimately a single particle, but is made up of far smaller subatomic particles. Subsequent research determined the exact atomic structure which led to Rutherford's gold foil experiment. Scientists eventually discovered that atoms have a positively charged nucleus (with an exact atomic number of charges) in the center, with a radius of about 1.2 × 10 meters × [atomic mass number]. Electrons were found to be even smaller. Later, scientists found the expected number of electrons (the same as the atomic number) in an atom by using X-rays. When an X-ray passes through an atom, some of it is scattered, while the rest passes through the atom.
Rutherford model | Contribution to modern science
This was in a gold atom known to be 10 metres or so in radius—a very surprising finding, as it implied a strong central charge less than 1/3000th of the diameter of the atom.
Rutherford model | Experimental basis for the model
In 1905 JPVM joined with WHB in his experiments & then later publishing his own experiments up to 1909, & in particular a paper on the Scattering of Beta Rays of Radium published in England in the Phil Mag. One of the results of great significance from this experiment with thin foils of gold, aluminium, silver & paper was that for the thinnest of foils the beta particles passing through were only scattered once, the implication to Rutherford of this was that within the atom there was a lot of empty space. Rutherford in 1911 published a very famous paper on the Scattering of Alpha & Beta particles & the Structure of the Atom the Rutherford Model as a mini solar system or nuclear atom in which he mentions JPVM's results.
John Madsen (physicist) | 1900–1911
Rutherford's research, and work done under him as laboratory director, established the nuclear structure of the atom and the essential nature of radioactive decay as a nuclear process. Patrick Blackett, a research fellow working under Rutherford, using natural alpha particles, demonstrated "induced" nuclear transmutation. Rutherford's team later, using protons from an accelerator, demonstrated "artificially-induced" nuclear reactions and transmutation. He is known as the father of nuclear physics. Rutherford died too early to see Leó Szilárd's idea of controlled nuclear chain reactions come into being. However, a speech of Rutherford's about his artificially-induced transmutation in lithium, printed in 12 September 1933 London paper "The Times", was reported by Szilárd to have been his inspiration for thinking of the possibility of a controlled energy-producing nuclear chain reaction.
Ernest Rutherford | Nuclear physics
Rutherford used alpha particles emitted by radium bromide to infer that J. J. Thomson's Plum pudding model of the atom was fundamentally flawed. In Rutherford's gold foil experiment conducted by his students Hans Geiger and Ernest Marsden, a narrow beam of alpha particles was established, passing through very thin (a few hundred atoms thick) gold foil. The alpha particles were detected by a zinc sulfide screen, which emits a flash of light upon an alpha particle collision. Rutherford hypothesized that, assuming the "plum pudding" model of the atom was correct, the positively charged alpha particles would be only slightly deflected, if at all, by the dispersed positive charge predicted.
Alpha particle | History of discovery and use
This would make the nuclear charge nearly equal to atomic number in smaller atoms, with some deviation from this rule for the largest atoms, such as gold. For example, Rutherford found the charge on gold to be about 100 units and thought perhaps that it might be exactly 98 (which would be close to half its atomic weight). But gold's place in the periodic table (and thus its atomic number) was known to be 79. Thus Rutherford did not make the proposal that the number of charges in the nucleus of an atom might be "exactly" equal to its place on the periodic table (atomic number).
Antonius van den Broek | Major contribution to science
In 1867 he developed an electromagnetic hammer, with which one could use gold as a restorative material for a tooth gold foil filling easier and faster, and had it patented in 1873. In November 1875, he was honored for this work with the Elliott Cresson Medal, the highest award of the Franklin Institute of Philadelphia. He expanded the technique for condensing amalgam while laying amalgam fillings.
William Gibson A. Bonwill | Gold foil filling
The Rutherford formula (see below) further neglects the recoil kinetic energy of the massive target nucleus. The initial discovery was made by Hans Geiger and Ernest Marsden in 1909 when they performed the gold foil experiment in collaboration with Rutherford, in which they fired a beam of alpha particles (helium nuclei) at foils of gold leaf only a few atoms thick. At the time of the experiment, the atom was thought to be analogous to a plum pudding (as proposed by J. J. Thomson), with the negatively-charged electrons (the plums) studded throughout a positive spherical matrix (the pudding). If the plum-pudding model were correct, the positive "pudding", being more spread out than in the correct model of a concentrated nucleus, would not be able to exert such large coulombic forces, and the alpha particles should only be deflected by small angles as they pass through.
Rutherford scattering | Introduction
Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand–born British physicist who came to be known as the father of nuclear physics. "Encyclopædia Britannica" considers him to be the greatest experimentalist since Michael Faraday (1791–1867). In early work, Rutherford discovered the concept of radioactive half-life, the radioactive element radon, and differentiated and named alpha and beta radiation. This work was performed at McGill University in Montreal, Quebec, Canada. It is the basis for the Nobel Prize in Chemistry he was awarded in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances", for which he was the first Canadian and Oceanian Nobel laureate.
Ernest Rutherford | Introduction
Szilard had this idea while walking in London, on the same day. Rutherford's speech touched on the 1932 work of his students John Cockcroft and Ernest Walton in "splitting" lithium into alpha particles by bombardment with protons from a particle accelerator they had constructed. Rutherford realized that the energy released from the split lithium atoms was enormous, but he also realized that the energy needed for the accelerator, and its essential inefficiency in splitting atoms in this fashion, made the project an impossibility as a practical source of energy (accelerator-induced fission of light elements remains too inefficient to be used in this way, even today).
Ernest Rutherford | Nuclear physics
In this May 1911 paper, Rutherford only committed himself to a small central region of very high positive or negative charge in the atom. For concreteness, consider the passage of a high speed α particle through an atom having a positive central charge "N" "e", and surrounded by a compensating charge of "N" electrons. From purely energetic considerations of how far particles of known speed would be able to penetrate toward a central charge of 100 e, Rutherford was able to calculate that the radius of his gold central charge would need to be less (how much less could not be told) than 3.4 × 10 metres.
Rutherford model | Experimental basis for the model
Carl Stumpf was a participant in this study. However, there has been some ongoing dispute on the experiment itself, as the fact that Fechner deliberately discarded results of the study ill-fitting to his needs became known, with many mathematicians including Mario Livio refuting the result of the experiment.
Gustav Fechner | Golden section hypothesis
The first estimate of a nuclear charge radius was made by Hans Geiger and Ernest Marsden in 1909, under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester, UK. The famous experiment involved the scattering of α-particles by gold foil, with some of the particles being scattered through angles of more than 90°, that is coming back to the same side of the foil as the α-source. Rutherford was able to put an upper limit on the radius of the gold nucleus of 34 femtometres. Later studies found an empirical relation between the charge radius and the mass number, "A", for heavier nuclei ("A" > 20): where the empirical constant "r" of 1.2–1.5 fm can be interpreted as the Compton wavelength of the proton.
Charge radius | History
Jack Steinberger, working on what were then considered high energy experiments at the Nevis Laboratory of Columbia. Goldhaber became a naturalized citizen of the United States in 1953. The Goldhabers moved to Berkeley, California in 1953 when Gerson was given a job as an assistant professor at the University of California. While Goldhaber had previously worked in physical chemistry, she was able to transition to high energy physics and form a collaboration with her husband working on nuclear emulsion. The Goldhabers hoped to use their nuclear emulsion technique with the newly opened Bevatron — at the time the highest energy accelerator in operation — and it was through their methods that they observed some of the earliest interactions between K mesons and protons.
Sulamith Goldhaber | Biography
Geiger was born at Neustadt an der Haardt, Germany. He was one of five children born to the Indologist Wilhelm Ludwig Geiger, who was a professor at the University of Erlangen. In 1902, Geiger started studying physics and mathematics at the University of Erlangen and was awarded a doctorate in 1906. His thesis was on electrical discharges through gases. He received a fellowship to the University of Manchester and worked as an assistant to Arthur Schuster. In 1907, after Schuster's retirement, Geiger began to work with his successor, Ernest Rutherford, and in 1908, along with Ernest Marsden, conducted the famous Geiger–Marsden experiment (also known as the "gold foil experiment").
Hans Geiger | Biography
After receiving his Ph.D. in 1977, Goldston was offered a staff position at the Princeton Plasma Physics Laboratory. His early work there involved studying how plasmas are heated by energetic ions, with the ultimate goal being the construction of a fusion reactor, a device that would generate fusion reactions of light nuclei rather than fission reactions of heavy nuclei. In a 1979 interview, Goldston explained the significance of his research: "If we can accomplish this, we will have created an inexhaustible fuel, which will burn without leaving the quantities of dangerous radioactive waste generated by the atomic power plants we have now." Later that decade, Goldston produced physical evidence that fast ions circulating in toroidal magnetically confined plasmas such as the tokamak configuration slowed down in good agreement with classical collision theory, thus providing a physical underpinning for the further development of the powerful neutral beam systems which have heated and driven electric current in successive generations of tokamaks and other magnetic plasma confinement devices such as stellarators.
Robert J. Goldston | Career
Unable to convince Fermi that this was the case, Szilard set out on his own. He obtained permission from the head of the Physics Department at Columbia, George B. Pegram, to use a laboratory for three months. To fund his experiment, he borrowed $2,000 from a fellow inventor, Benjamin Liebowitz. He wired Frederick Lindemann at Oxford and asked him to send a beryllium cylinder. He convinced Walter Zinn to become his collaborator, and hired Semyon Krewer to investigate processes for manufacturing pure uranium and graphite. Szilard and Zinn conducted a simple experiment on the seventh floor of Pupin Hall at Columbia, using a radium–beryllium source to bombard uranium with neutrons.
Leo Szilard | Columbia University
Since Maurice's lab was only set up for nuclear physics research, Gertrude Goldhaber took up research in that field as well. During this time Gertrude and Maurice Goldhaber had two sons: Alfred and Michael. Goldhaber was eventually given a soft-money line by the department to help support her research. Goldhaber studied neutron-proton and neutron-nucleus reaction cross sections in 1941, and gamma radiation emission and absorption by nuclei in 1942. Around this time she also observed that spontaneous nuclear fission is accompanied by the release of neutrons — a result that had been theorized earlier but had yet to be shown.
Gertrude Scharff Goldhaber | Career
Ernest Rutherford was Langsworthy Professor of Physics at the Victoria University of Manchester (now the University of Manchester). He had already received numerous honours for his studies of radiation. He had discovered the existence of alpha rays, beta rays, and gamma rays, and had proved that these were the consequence of the disintegration of atoms. In 1906, he received a visit from a German physicist named Hans Geiger, and was so impressed that he asked Geiger to stay and help him with his research. Ernest Marsden was a physics undergraduate student studying under Geiger. Alpha particles are tiny, positively charged particles that are spontaneously emitted by certain substances such as uranium and radium.
Geiger–Marsden experiment | Background
His conclusion on the formula proved to be incorrect but offered a fair estimate for later scientists to jump from.
Fulminating gold | History
At first, he continued his work on crystals on his own but when Bohr's student became ill, he was assigned the urgent task of working on the helium problem. Hylleraas modified the first attempt in two important ways: he replaced the incomplete bound-state hydrogenic functions by the complete Laguerre functions and reduced the number of co-ordinates from 6 to 3, namely the distances of the two electrons from the nucleus and the angle between the position vectors of the two electrons. Then, with the aid of a mechanical desk calculator obtained result in much better agreement with experiment. The result was well received but the discrepancy of 0.12 eV continued to bother him.
Egil Hylleraas | The Golden Age of Atomic Physics
He had, for example, badly miscalculated the numbers of particles in atoms of silver and gold, and he had assumed all subatomic particles to be the same, except for their electric charge, which he thought could be changed at will. Just as Hunter was unveiling his transmutation claims, chemists William Ramsay and Frederick Soddy reported one of the most important findings of early atomic science. Their study of radium radioactivity had revealed that radium, as it decays, transmutes into helium. Hunter, in response to that news, wrote Ramsay to tell him that he had already achieved the transmutation of silver into gold.
Rudolph M. Hunter | Transmutation
In Britain, a number of scientists considered whether an atomic bomb was practical. At the University of Liverpool, Chadwick and the Polish refugee scientist Joseph Rotblat tackled the problem, but their calculations were inconclusive. At Cambridge, Nobel Prize in Physics laureates George Paget Thomson and William Lawrence Bragg wanted the government to take urgent action to acquire uranium ore. The main source of this was the Belgian Congo, and they were worried that it could fall into German hands. Unsure as to how to go about this, they spoke to Sir William Spens, the master of Corpus Christi College, Cambridge.
Tube Alloys | Frisch–Peierls memorandum
Gold began discussing problems in physics with Hoyle and Bondi again, centering on the issues over redshift and Hubble's law. This led the three to all start questioning the Big Bang theory originally proposed by Georges Lemaître in 1931 and later advanced by George Gamow, which suggested that the universe expanded from an extremely dense and hot state and continues to expand today. As recounted in a 1978 interview with physicist and historian Spencer R. Weart, Gold believed that there was reason to think that the creation of matter was "done all the time and then none of the problems about fleeting moments arise.
Thomas Gold | Steady-state theory
The earliest of several probability puzzles related to the Monty Hall problem is Bertrand's box paradox, posed by Joseph Bertrand in 1889 in his "Calcul des probabilités". In this puzzle, there are three boxes: a box containing two gold coins, a box with two silver coins, and a box with one of each. After choosing a box at random and withdrawing one coin at random that happens to be a gold coin, the question is what is the probability that the other coin is gold. As in the Monty Hall problem, the intuitive answer is , but the probability is actually .
Monty Hall problem | History
They counted the number of scintillations per minute that each foil produced on the screen. They divided the number of scintillations per minute by the respective foil's air equivalent, then divided again by the square root of the atomic weight (Geiger and Marsden knew that for foils of equal stopping power, the number of atoms per unit area is proportional to the square root of the atomic weight). Thus, for each metal, Geiger and Marsden obtained the number of scintillations that a fixed number of atoms produce. For each metal, they then divided this number by the square of the atomic weight, and found that the ratios were more or less the same.
Geiger–Marsden experiment | The 1913 experiment
In 1980, he transmuted several thousand atoms of bismuth into gold at the Lawrence Berkeley Laboratory. His experimental technique, using nuclear physics, was able to remove protons and neutrons from the bismuth atoms. Seaborg's technique would have been far too expensive to enable routine manufacturing of gold, but his work was close to the mythical Philosopher's Stone. In 1981, Seaborg became a founding member of the World Cultural Council.
Glenn T. Seaborg | Return to California
At most small deflections should occur as the alpha particles passed almost unhindered through the foil. Instead, when Marsden positioned the detector on the same side of the foil as the alpha particle source, he immediately detected a noticeable backscattered signal. According to Rutherford, "It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you." Rutherford interpreted the result of the Geiger–Marsden experiment as an indication of a Coulomb collision with a single massive positive particle.
Rutherford backscattering spectrometry | The Geiger–Marsden experiment
In 1950, John Wheeler was setting up a secret H-bomb research lab at Princeton University. Lyman Spitzer, Jr., an avid mountaineer, was aware of this program and suggested the name "Project Matterhorn". Spitzer, a professor of Astronomy, had for many years been involved in the study of very hot rarefied gases in interstellar space. While leaving for a ski trip to Aspen in February 1951, his father called and told him to read the front page of the "New York Times". The paper had a story about claims released the day before in Argentina that a relatively unknown German scientist named Ronald Richter had achieved nuclear fusion in his Huemul Project.
Princeton Plasma Physics Laboratory | History
The total cost of the project was estimated at US$300 million (2003 value). In 1951 Richter announced that he had achieved controlled nuclear fusion under laboratory conditions, a claim later proven false: it transpired that Richer had simply exploded hydrogen in an electric arc.
Ronald Richter | Argentina
This apparatus allowed them to study the nuclear cross section of the various reactions, and it was their work that produced the 100 keV figure. The chance that any given deuteron will hit one of the deuterium atoms in the metal foil is vanishingly small. The experiment only succeeded because it ran for extended periods, and the rare reactions that did occur were so powerful that they could not be missed. But as the basis of a system for power production it simply wouldn't work; the vast majority of the accelerated deuterons goes right through the foil without undergoing a collision, and all the energy put into accelerating it is lost.
Colliding beam fusion | Direct acceleration
In 1932, physicist Ernest Rutherford discovered that when lithium atoms were "split" by protons from a proton accelerator, immense amounts of energy were released in accordance with the principle of mass–energy equivalence. However, he and other nuclear physics pioneers Niels Bohr and Albert Einstein believed harnessing the power of the atom for practical purposes anytime in the near future was unlikely. The same year, Rutherford's doctoral student James Chadwick discovered the neutron, which was immediately recognized as a potential tool for nuclear experimentation because of its lack of an electric charge. Experiments bombarding materials with neutrons led Frédéric and Irène Joliot-Curie to discover induced radioactivity in 1934, which allowed the creation of radium-like elements.
Nuclear power | Origins
By the autumn of 1939, Gold had gained a place at University College (transferred to King’s and Bristol, because of the war) to study chemistry, but the following summer all Austrian and German aliens were interned, mostly in Douglas, Isle of Man. In the camp Gold met Hans Pelzer, one of the founders of transition state theory, who taught Victor some quantum mechanics.
Victor Gold (chemist) | Introduction
Using the Bevatron and the nuclear emulsion technique Goldhaber was the first to observe mass splitting in charged E hyperons as well as the first nuclear interactions of the antiproton. In the 1960s the Goldhabers realized that they should begin using the bubble chamber to continue their studies instead of nuclear emulsion so they formed the "Goldhaber-Trilling Group" with George Trilling. Goldhaber quickly became a renowned expert in hydrogen bubble chamber physics, accruing a lengthy list of invited papers and conference talks. The Goldhabers were the first to measure the spin of the K* meson and the first to study the simultaneous production of pairs of resonant states.
Sulamith Goldhaber | Biography
The plum pudding model had predicted that the alpha particles should come out of the foil with their trajectories being at most slightly bent. But Rutherford instructed his team to look for something that shocked him to observe: a few particles were scattered through large angles, even completely backwards in some cases. He likened it to firing a bullet at tissue paper and having it bounce off. The discovery, with Rutherford's analysis of the data in 1911, led to the Rutherford model of the atom, in which the atom had a very small, very dense nucleus containing most of its mass, and consisting of heavy positively charged particles with embedded electrons in order to balance out the charge (since the neutron was unknown).
Nuclear physics | Rutherford's team discovers the nucleus
Immediately after the war, Hoyle and Bondi returned to Cambridge, while Gold stayed with naval research until 1947. He then began working at Cambridge's Cavendish Laboratory to help construct the world's largest magnetron, a device invented by two British scientists in 1940 that generated intense microwaves for radar. Soon after, Gold joined R. J. Pumphrey, a zoologist at the Cambridge Zoology Laboratory who had served as the deputy head of radar naval research during the war, to study the effect of resonance on the human ear. He found that the degree of resonance observed in the cochlea was not in accordance with the level of damping that would be expected from the viscosity of the watery liquid that fills the inner ear.
Thomas Gold | Work at Cambridge
This recoil target was made by an electroplating technique, developed by Alfred Chetham-Strode. This technique gave a very high yield, which was absolutely necessary when working with such a rare and valuable product as the einsteinium target material. The recoil target consisted of 10 atoms of Es which were deposited electrolytically on a thin gold foil. It was bombarded by 41 MeV alpha particles in the Berkeley cyclotron with a very high beam density of 6×10 particles per second over an area of 0.05 cm. The target was cooled by water or liquid helium, and the foil could be replaced.
Mendelevium | Discovery
He also investigated using uranium hydride instead of uranium metal, but its efficiency turned out to be "negligible or less". He continued to push his ideas for a fusion weapon even though it had been put on a low priority during the war (as the creation of a fission weapon proved to be difficult enough). On a visit to New York, he asked Maria Goeppert-Mayer to carry out calculations on the Super for him. She confirmed Teller's own results: the Super was not going to work.
Edward Teller | Los Alamos Laboratory
It may seem that the probability that the remaining coin is gold is , but in truth, the probability is actually . Two problems that are very similar are the Monty Hall problem and the Three Prisoners problem.
Bertrand's box paradox | Solution
Rutherford's speech in part, read:
Ernest Rutherford | Nuclear physics
The nucleus was discovered in 1911, as a result of Ernest Rutherford's efforts to test Thomson's "plum pudding model" of the atom. The electron had already been discovered by J.J. Thomson himself. Knowing that atoms are electrically neutral, J.J.Thomson postulated that there must be a positive charge as well. In his plum pudding model, Thomson suggested that an atom consisted of negative electrons randomly scattered within a sphere of positive charge. Ernest Rutherford later devised an experiment with his research partner Hans Geiger and with help of Ernest Marsden, that involved the deflection of alpha particles (helium nuclei) directed at a thin sheet of metal foil.
Atomic nucleus | History
In the summer of 1944 Goldstine had a chance encounter with the prominent mathematician John von Neumann on a railway platform in Aberdeen, Maryland, and Goldstine described his project at the University of Pennsylvania. Unknown to Goldstine, von Neumann was then working on the Manhattan Project, which was aiming to build the first atomic bomb. The calculations needed for this project were also daunting.
Herman Goldstine | Meeting John von Neumann
The medal is named after Ernest Rutherford, the New Zealand experimental physicist and Nobel Laureate, who pioneered the orbital theory of the atom.
Rutherford Medal (Royal Society of New Zealand) | Introduction
Maurice Goldhaber (April 18, 1911 – May 11, 2011) was an American physicist, who in 1957 (with Lee Grodzins and Andrew Sunyar) established that neutrinos have negative helicity.
Maurice Goldhaber | Introduction
Bird followed this tradition and was particularly influenced by the work of William Prout, an expert in chemical physiology. Bird became well known for his knowledge of chemistry. An early example dates from 1832, when he commented on a paper on the copper sulphate test for arsenic poisoning, delivered by his future brother-in-law R. H. Brett to the Pupils' Physical Society. Bird criticised the test's positive result when a green precipitate is formed, claiming the test was inconclusive because precipitates other than copper arsenite can produce the same green colour. Bird did not limit himself to challenging his future brother-in-law.
Golding Bird | Collateral sciences
This led him to the conclusion that the atom's positive charge could not be diffuse but instead must be concentrated in a single massive core: the atomic nucleus. Calculations indicated that the charge necessary to accomplish this deflection was approximately 100 times the charge of the electron, close to the atomic number of gold. This led to the development of the Rutherford model of the atom in which a positive nucleus made up of "N"e positive particles, or protons, was surrounded by "N" orbiting electrons of charge -e to balance the nuclear charge. This model was eventually superseded by the Bohr atom, incorporating some early results from quantum mechanics.
Rutherford backscattering spectrometry | The Geiger–Marsden experiment
In his "Reminiscences", Hylleraas referred to the period 1925–1930 as the "Golden Age" of atomic physics. It was a time when Bohr's theory of the atom was being replaced by the new quantum mechanics. By 1926, the one-electron hydrogen problem had been solved and Heisenberg had formulated the two-electron helium problem quantum mechanically but a simple first-order perturbation treatment yielded an ionization potential considerably in error with experimental measurement. Born considered it crucial for quantum mechanics to provide a result in much better agreement with experiment. When Hylleraas arrived in Göttingen he was disappointed to learn that Born had abandoned crystallography.
Egil Hylleraas | The Golden Age of Atomic Physics
The Fellows of the Royal Society were less convinced, however, and asked him to repeat the experiments in the presence of some of the members of the Society. Price seemed less than happy to do this. He claimed that his powders were exhausted and preparation of new samples would cost him time and money and be damaging to his health. He also protested that the cost of preparing the gold or silver by this method was not economical, as it cost £17 to make an ounce of gold, which was only valued at £4. The Royal Society insisted on the repetition of the experiments and reminded Price that, as a member, he was calling the honour of the Society into question.
James Price (chemist) | Challenged by other Fellows
His PhD was awarded in 1951, under the supervision of Professor Herrington, for his thesis on the diffusion of electrogenerated hydrogen through palladium foils. He met Sheila, his future wife, as a student and remained married to her for 62 years.
Martin Fleischmann | Personal life
Ernest Rutherford accepted Cockcroft as a research student at the Cavendish Laboratory on the recommendation of Miles Walker and the director of research at Metropolitan Vickers. Cockcroft enrolled as a PhD student in 1924, with a Foundation Scholarship of St John's College, and a State Scholarship. Under Rutherford's supervision, he wrote his doctoral thesis "On phenomena occurring in the condensation of molecular streams on surfaces", which was published in the "Proceedings of the Royal Society". He was awarded his doctorate on 6 September 1925. During this time he was an assistant to the Russian physicist Peter Kapitza, who was working on the physics of magnetic fields in extremely low temperatures.
John Cockcroft | Nuclear research
While there, Gold attracted some controversy by suggesting that the interaction between charged particles from the Sun with the Earth's magnetic field in creating magnetic storms in the upper atmosphere was an example of a collisionless shock wave. The theory was widely disputed, until American scientists in 1957 discovered that Gold's theory held up to mathematical scrutiny by conducting a simulation using a shock tube. Gold resigned from the Royal Observatory following Spencer-Jones's retirement and moved to the United States in 1956, where he served as Professor of Astronomy (1957–1958) and Robert Wheeler Wilson Professor of Applied Astronomy (1958–1959) at Harvard University.
Thomas Gold | Astrophysics research
Thomas Gold (also known as Tommy Gold), (May 22, 1920 – June 22, 2004) was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society (London). Gold was one of three young Cambridge scientists who in 1948 proposed the now mostly abandoned "steady state" hypothesis of the universe. Gold's work crossed academic and scientific boundaries, into biophysics, astronomy, aerospace engineering, and geophysics.
Thomas Gold | Introduction
Goldhaber was born on February 20, 1924 in Germany. His Jewish family fled Nazi Germany to Egypt and Goldhaber earned a master's degree in physics in 1947 from the Hebrew University of Jerusalem. Goldhaber was awarded his Ph.D. in 1950 from the University of Wisconsin and became a naturalized citizen of the United States in 1953 while he was on the faculty of Columbia University. Goldhaber became a professor at the University of California, Berkeley and did additional work at the Lawrence Berkeley National Laboratory. At Berkeley, Goldhaber was part of a particle physics research team that used photographic emulsion to track the movements of subatomic particles in proton-proton scattering experiments that led to the identification of the antiproton, a discovery that earned Owen Chamberlain and Emilio G.
Gerson Goldhaber | Biography
He tried but failed to make a rapid return to the gold standard.
Hugh McCulloch | Introduction
Using the new 27-inch cyclotron, the team at Berkeley discovered that every element that they bombarded with recently discovered deuterium emitted energy, and in the same range. They, therefore, postulated the existence of a new and hitherto unknown particle that was a possible source of limitless energy. William Laurence of "The New York Times" described Lawrence as "a new miracle worker of science". At Cockcroft's invitation, Lawrence attended the 1933 Solvay Conference in Belgium. This was a regular gathering of the world's top physicists. Nearly all were from Europe, but occasionally an outstanding American scientist like Robert A. Millikan or Arthur Compton would be invited to attend.
Ernest Lawrence | Reception
After completing his studies at Manchester he spent two years as a research associate at Cavendish Laboratory in Cambridge. He was a Fellow at the University of California, Berkeley until 1960. While at Berkeley in 1960, together with Andrew Sessler, he made the prediction that liquid helium-3 would experience superfluidity, flowing without friction, at temperatures very close to absolute zero. The theory was later confirmed experimentally. At this stage he returned to the United Kingdom where he spent some time as a lecturer at the University of Birmingham. As a result of his work at Berkeley, Emery was invited to join the Brookhaven National Laboratory's Physics Department in 1964.
Victor Emery | Career in Theoretical Physics
In 1951, at a meeting of the Royal Astronomical Society, Gold proposed that the source of recent radio signals detected from space was outside the Milky Way galaxy, much to the derision of radio astronomer Martin Ryle and several mathematical cosmologists. However, a year later, a distant source was identified and Gold announced at an International Astronomical Union meeting in Rome that his theory had been proven. Ryle would later take Gold's argument as proof of extragalactic evolution, claiming that it invalidated the steady-state theory. Gold left Cambridge in 1952 to become the chief assistant to Astronomer Royal Harold Spencer Jones at the Royal Greenwich Observatory in Herstmonceux, Sussex, England.
Thomas Gold | Astrophysics research
His next contribution to economical science was a series of articles on the gold question, published partly in Fraser's Magazine, in which the probable consequences of the increased supply of gold attendant on the Australian and Californian gold discoveries were analysed with great skill and ability. And a critical article on M. Chevaliers' work, "On the Probable Fall in the Value of Gold", appeared in the "Edinburgh Review" for July 1860.
John Elliott Cairnes | Biography
Bird used his position as head of the department of electricity and galvanism to further his research efforts and to aid him in teaching his students. He was interested in electrolysis and repeated the experiments of Antoine César Becquerel, Edmund Davy and others to extract metals in this way. He was particularly interested in the possibility of detecting low levels of heavy metal poisons with this technique, pioneered by Davy. Bird also studied the properties of albumen under electrolysis, finding that the albumen coagulated at the anode because hydrochloric acid was produced there. He corrected an earlier erroneous conclusion by W.
Golding Bird | Electrochemistry
Between 1908 and 1913, Rutheford and his colleagues performed a series of experiments in which they bombarded thin foils of metal with alpha particles. They spotted alpha particles being deflected by angles greater than 90°. To explain this, Rutherford proposed that the positive charge of the atom is not distributed throughout the atom's volume as Thomson believed, but is concentrated in a tiny nucleus at the center. Only such an intense concentration of charge could produce an electric field strong enough to deflect the alpha particles as observed.
Atomic theory | Discovery of the nucleus
Along with the pit, the whole physics package was also informally nicknamed "Christy['s] Gadget". Of the several allotropes of plutonium, the metallurgists preferred the malleable δ (delta) phase. This was stabilized at room temperature by alloying it with gallium. Two equal hemispheres of plutonium-gallium alloy were plated with silver, and designated by serial numbers HS-1 and HS-2. The radioactive core generated 15 W of heat, which warmed it up to about , and the silver plating developed blisters that had to be filed down and covered with gold foil; later cores were plated with nickel instead. The Trinity core consisted of just these two hemispheres.
Trinity (nuclear test) | The Gadget
"Dear Professor . . . I would be eternally indebted if you could find time to read my work," he began. "In 1953 Einstein sent me a reply, from Princeton, New Jersey, but it was written in German. So I ran down to my barber shop (in Copenhagen) to have my barber translate it for me. Through that summer and fall, we exchanged about a half dozen letters. The local press picked up on these stories which then caught the attention of physicist Niels Bohr and others. Suddenly doors of opportunity were swinging open for me". (Perimeter Institute for Theoretical Physics, 2005) Einstein's initial reply:
John Moffat (physicist) | Interest in physics
His body reflected neutrons back into the stack. Out of the corner of his eye he saw that the red lamps that flickered intermittently when neutrons were being emitted, were 'glowing continuously'. Realizing what was happening, Frisch quickly scattered the bars with his hand. Later he calculated that the radiation dose was "quite harmless" but that if he "had hesitated for another two seconds before removing the material ... the dose would have been fatal". "In two seconds he received, by the generous standards of the time, a full day's permissible dose of neutron radiation." In this way his experiments determined the exact masses of uranium required to fire the Little Boy bomb over Hiroshima.
Otto Robert Frisch | Manhattan Project
At this point, Hahn decided that he first needed to know more about the subject, so he wrote to the leading expert on the field, Ernest Rutherford. Rutherford agreed to take Hahn on as an assistant, and Hahn's parents undertook to pay Hahn's expenses. From September 1905 until mid-1906, Hahn worked with Rutherford's group in the basement of the Macdonald Physics Building at McGill University in Montreal. There was some scepticism about the existence of radiothorium, which Bertram Boltwood memorably described as a compound of thorium X and stupidity. Boltwood was soon convinced that it did exist, although he and Hahn differed on what its half life was.
Otto Hahn | Discovery of radio thorium, and other "new elements"
Edward Creutz, the head of the group responsible for fabricating the uranium, wanted a metal sphere the size of an orange for his experiments. With Westinghouse's process, it would have cost $200,000 and taken a year to produce. The other major problem was the purity of the uranium. Impurities could act as neutron poisons and prevent a nuclear reactor from working, but the uranium oxide that Fermi wanted for his experimental reactor contained unacceptably large amounts of impurities. As a result, references published before 1942 typically listed its melting point at around when pure uranium metal actually melts at .
Frank Spedding | Manhattan Project
[which was] known to extend out to a distance of the order of 10 Earth radii". In 1960, Gold collaborated again with Fred Hoyle to show that magnetic energy fueled solar flares and that flares were triggered when opposite magnetic loops interact and release their stored energy.
Thomas Gold | Astrophysics research
He had first formulated such an idea in 1933 upon reading Ernest Rutherford's disparaging remarks about generating power from his team's 1932 experiment using protons to split lithium. However, Szilárd had not been able to achieve a neutron-driven chain reaction with neutron-rich light atoms. In theory, if the number of secondary neutrons produced in a neutron-driven chain reaction was greater than one, then each such reaction could trigger multiple additional reactions, producing an exponentially increasing number of reactions. Szilárd teamed up with Fermi to build a nuclear reactor from natural uranium at Columbia University, where George B. Pegram headed the physics department.
Einstein–Szilárd letter | Origin
Lawrence was asked to give a presentation on the cyclotron. Lawrence's claims of limitless energy met a very different reception in Solvay. He ran into withering skepticism from the Cavendish Laboratory's James Chadwick, the physicist who had discovered the neutron in 1932, for which he was awarded the Nobel Prize in 1935. In a British accent that sounded condescending to American ears, Chadwick suggested that what Lawrence's team was observing was contamination of their apparatus. When he returned to Berkeley, Lawrence mobilized his team to go painstakingly over the results to gather enough evidence to convince Chadwick. Meanwhile, at the Cavendish laboratory, Rutherford and Mark Oliphant found that deuterium fuses to form helium-3, which causes the effect that the cyclotroneers had observed.
Ernest Lawrence | Reception
He became a professor in 1937. In 1931 Rabi returned to particle beam experiments. In collaboration with Gregory Breit, he developed the Breit-Rabi equation, and predicted that the Stern–Gerlach experiment could be modified to confirm the properties of the atomic nucleus. The next step was to do so. With the help of Victor W. Cohen, Rabi built a molecular beam apparatus at Columbia. Their idea was to employ a weak magnetic field instead of a strong one, with which they hoped to detect the nuclear spin of sodium. When the experiment was conducted, four beamlets were found, from which they deduced a nuclear spin of .
Isidor Isaac Rabi | Molecular Beam Laboratory
These were followed by experiments in 1961 by Miyake, Narasimham and Ramanamurty and sponsored by TIFR. During 1984, Naba Kumar Mondal, TIFR, and Prof. Ito, Osaka City University, Japan, performed experimental studies on proton decay and indirectly observed the scatter of muons. Murali and Balasubramaniam briefly assisted Mondal and Ito as research assistants.
Particle experiments at Kolar Gold Fields | Initial experiments
After beginning his physics studies at the University of Berlin, he earned his doctorate at Cambridge University in 1936, belonging to Magdalene College.
Maurice Goldhaber | Education
The invention that brought Lawrence to international fame started out as a sketch on a scrap of a paper napkin. While sitting in the library one evening in 1929, Lawrence glanced over a journal article by Rolf Widerøe, and was intrigued by one of the diagrams. This depicted a device that produced high-energy particles by means of a succession of small "pushes". The device depicted was laid out in a straight line using increasingly longer electrodes. At the time, physicists were beginning to explore the atomic nucleus. In 1919, the New Zealand physicist Ernest Rutherford had fired alpha particles into nitrogen and had succeeded in knocking protons out of some of the nuclei.
Ernest Lawrence | Invention
At Rutherford's behest, Geiger and Marsden performed a series of experiments where they pointed a beam of alpha particles at a thin foil of metal and measured the scattering pattern by using a fluorescent screen. They spotted alpha particles bouncing off the metal foil in all directions, some right back at the source. This should have been impossible according to Thomson's model; the alpha particles should have all gone straight through. Obviously, those particles had encountered an electrostatic force far greater than Thomson's model suggested they would. Furthermore, only a small fraction of the alpha particles were deflected by more than 90°.
Geiger–Marsden experiment | The outcome of the experiments
The initial discovery was quite serendipitous. Rosenberg was looking into the effects of an electric field on the growth of bacteria. He noticed that bacteria ceased to divide when placed in an electric field and eventually traced the cause of this phenomenon to the platinum electrode he was using.
Barnett Rosenberg | Introduction
Walton was awarded his PhD in 1931 and remained at Cambridge as a researcher until 1934. During the early 1930s Walton and John Cockcroft collaborated to build an apparatus that split the nuclei of lithium atoms by bombarding them with a stream of protons accelerated inside a high-voltage tube (700 kilovolts). The splitting of the lithium nuclei produced helium nuclei. This was experimental verification of theories about atomic structure that had been proposed earlier by Rutherford, George Gamow, and others. The successful apparatus – a type of particle accelerator now called the Cockcroft-Walton generator – helped to usher in an era of particle-accelerator-based experimental nuclear physics.
Ernest Walton | Early years
He demonstrated his "transmutation" of uranium oxide into radium to physicists of the University of Cologne, but declined to explain his procedure. When the newspapers took up his claims, the "Physikalisch-Technische Reichsanstalt" examined them and found them to be fraudulent. In May 1928, as a result of the publicity Kurschildgen now enjoyed, the apothecary of his hometown Hilden had a bust of Kurschildgen installed in town, mockingly dedicated to the "genius goldmaker". In 1929, Kurschildgen returned to the gold-making business. He unsuccessfully contacted the German president Paul von Hindenburg as well as "Reichsbank" president Hjalmar Schacht with proposals to manufacture gold to pay back Germany's World War I reparations.
Heinz Kurschildgen | Weimar Republic: gold and radium
Gold spent most of his nearly 15 months of internment in a camp in Canada, after which he returned to England and reentered Cambridge University, where he abandoned his study of mechanical sciences for physics. After graduating with a pass (Ordinary) degree in June 1942, Gold worked briefly as an agricultural labourer and lumberjack in northern England before joining Bondi and Fred Hoyle on naval research into radar ground clutter near Dunsfold, Surrey. The three men would spend their off-duty hours in "intense and wide-ranging scientific discussion" on topics such as cosmology, mathematics and astrophysics. Within months, Gold was placed in charge of constructing new radar systems.
Thomas Gold | Early life
Geiger and Marsden then tested how the scattering varied with the thickness of the foil (i.e. if "s ∝ t"). They constructed a disc (S) with six holes drilled in it. The holes were covered with metal foil (F) of varying thickness, or none for control. This disc was then sealed in a brass ring (A) between two glass plates (B and C). The disc could be rotated by means of a rod (P) to bring each window in front of the alpha particle source (R). On the rear glass pane was a zinc sulfide screen (Z). Geiger and Marsden found that the number of scintillations that appeared on the zinc sulfide screen was indeed proportional to the thickness as long as said thickness was small.
Geiger–Marsden experiment | The 1913 experiment