  Quantum mechanics thinks that all atoms do not have permanent electric dipole
moment (EDM) because of their spherical symmetry. Therefore, there is no polar
atom in nature except for polar molecules. The electric susceptibility Xe
caused by the orientation of polar substances is inversely proportional to the
absolute temperature T while the induced susceptibility of atoms is temperature
independent. Using special capacitors our experiments discovered that
directional motion of Rb atoms in a non-uniform electric field and ground state
Rb atom is polar atom with a large EDM: d(Rb) =2.72*10-29C.m = 1.70*10-8e.cm.
The experiment showed that the relationship between Xe of Rb vapor and T is
just Xe =B/T, where the slope B =380(k) as polar molecules. Its capacitance C
at different voltage V was measured. The C-V curve shows that the saturation
polarization of Rb vapor has be observed when E more than 8.5*104V/m. New
example of CP (charge conjugation and parity) violation occurred in Rb atoms
(see arXiv 0809.4767). If Rb atom has a large EDM, why the linear Stark effect
has not been observed? The article discussed the question thoroughly. Our
results are easy to be repeated because the details of the experiment are
described in the article.
