  Inelastic proton scattering under extreme forward angles including $0^\circ$
and at energies of a few hundred MeV has been established as a new
spectroscopic tool for the study of complete dipole strength distributions in
nuclei. Such data allow an extraction of the electric dipole polarizability
which provides important constraints parameters of the symmetry energy, which
determine the neutron skin thickness and the equation of state (EOS) of
neutron-rich matter. Also new insight into the much-debated nature of the pygmy
dipole resonance (PDR) is obtained. Additionally, the isovector spin-M1
resonance can be studied in heavy nuclei, where only limited experimental
information exists so far. Together with much improved results on the isoscalar
spin-M1 strength distributions in $N = Z$ nuclei, these data shed new light on
the phenomenon of quenching of the nuclear spin response. Using dispersion
matching techniques, high energy resolution ($\Delta E/E \leq 10^{-4} \,\,$
full width at half maximum, FWHM) can be achieved in the experiments. In
spherical-vibrational nuclei considerable fine structure is observed in the
energy region of the isovector giant dipole resonance (IVGDR). A quantitative
analysis of the fine structure with wavelet methods provides information on the
role of different damping mechanisms contributing to the width of the IVGDR.
Furthermore, level densities can be extracted from a fluctuation analysis at
excitation energies well above neutron threshold, a region hardly accessible by
other means. The combination of the gamma strength function (GSF) extracted
from the E1 and M1 strength distributions with the independently derived level
density permits novel tests of the Brink-Axel hypothesis underlying all
calculations of statistical model reaction cross sections in astrophysical
applications in the energy region of the PDR.
