Excitation of pairing vibrations in superfluid nuclei

Excitation of monopole pairing vibrations in superfluid nuclei in the two-neutron transfer reaction is studied within a kinetic model based on the semiclassical time-dependent Hartree - Fock - Bogolyubov theory. Using the anomalous (correlated) density response function, the monopole pairing mode and the amplitude of the dynamic variation of the pairing gap associated with this mode are obtained. It is shown that the pairing correlations give a coherent contribution to the spectroscopic factor for the excitation of monopole pairing vibrations in the two-neutron transfer reaction in superfluid nuclei. The contribution is determined by the distribution of neutron levels near the Fermi energy and does not exceed a few percent of the spectroscopic factor for the transfer of two neutrons to the ground state. This estimate is in agreement with experimental data for the ratio of the cross-section for excitation of the 0+-state in the (p, t)-reaction in the energy region of the monopole pairing mode, which is equal to the double pairing gap, to the cross section for excitation of the ground state in superfluid nuclei.