α-vibrations

The existence of states which change the number of particles in four and which are specifically excited in α-transfer reactions like (16O, 12C), (6Li, d), etc. is predicted, as a consequence of the existence of proton and neutron pairing vibrations which are strongly excited in two-particle transfer reactions. In particular a Jsup(π) = 0+ two-phonon α-vibration (4p-4h) state is expected at approximately 7 MeV of excitation in 208Pb and with a relative cross section sigma(204Hg → 7 MeV (208Pb))/sigma(208Pb → gs (212Po)) approximately 1. Similar states are expected in neighbouring nuclei. (Auth.)