← nuclearjs surface vibrations → E1 rates
Giant resonances
A photon near the big peak in the plot on the right is absorbed by the nucleus as a whole: its electric field pushes the protons one way and the neutrons the other, and the two fluids swing against each other. This isovector giant dipole resonance (GDR) is a broad peak that holds most of the dipole sum rule. In a deformed nucleus the swing along the long axis is slower than across it, and the peak splits in two. In-phase (isoscalar) modes of all the nucleons, the breathing monopole and the quadrupole, photons barely excite them (E2 absorption is weak), and they are measured with inelastic α and deuteron scattering.
Mode