Intruder states shell-model

Toward a Shell-Model Description of Intruder States and the Onset of Deformation... 

Basing on the nuclear shell-model and concentrating on the monopole,pairing and quadrupole corrections originating from the nucleon-nucleon force,both the appearance of low-lying 0+ intruder states near major closed shell (Z=50, 82)and sub-shell regions (Z=40,64) can be described.Moreover,a number of new facets related to the study of intruder states are presented. 

In this picture, the excitation of nucleons into shell-model intruder states leads to the coexistence of states with different deformations. Shell-model intruder states for the odd-mass Au isotopes, for example, are presented in fig. 2. Note that the h9 2 and i13y2 intruders drop rapidly as one goes more neutron deficient [ZGA80]. 

By studying the a decay of mass-separated nuclei in the region around Z=82 we have extended the knowledge of shell-model intruder states. The allowed a-decay branches of the odd-odd Bi nuclei connect across the Z=82 shell closure initial and final states of the same single-particle character. 

There are mainly two inter-related reasons why on would like to formulate a size-extensive theory involving incomplete model spaces (i) to bypass intruders, (ii) for calculating the low-lying EE s of a closed-shell ground state, one feels that a set of hole-particle determinants would suffice as a choice for a reasonable model space, which involves valence holes as well as valence particles. This is an IMS. 

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