Deep-lying hole states in nuclei

Abstract

The strength function for deep-lying hole states in a nucleus is examined from a many-body point of view. Due to their interaction with the compound state background, such single hole excitations are interpreted as quasihole states that are not eigenstates of the nuclear Hamiltonian. These states show up as giant resonances in the strength function, with position and width determined by the real and imaginary parts of the quasihole energy. A formal theory of the strength and fragmentation of such states is developed by splitting the self-energy into background and doorway state contributions. The theory is applied to the calculation of the strength function for the isotopes of Bn using doorway states of a collective nature that consist of a hole plus collective vibrations of the target nucleus. A microscopic description of both the collective excitations and the hole state that it dresses/ is given in terms of a modified Random Phase Approximation procedure that uses Green's functions for the individual single particle and single hole states that have been dressed by their interaction with the nuclear background. specific calculations for the isotope 115Sn, that are essentially free of adjustable parameters, shows excellent agreement with experiment.