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There are two nuclear models, the shell and the clustered lattice models, which explain the so-called shell effects observed in nuclear data. The responsible interaction in the former model is the spin-orbit term, whereas for the latter it is the nucleon-phonon term (short range force). In contrast to the short range force, the spin-orbit interaction shifts all single particle states. However its effect on the level density expression can also be interpreted as a change in the ground state. If it is true that for the shell model the shift of the ground state for the shell closure is opposite to that of pairing correlation, in contrast to the clustered lattice model prediction, experiments should decide between the two models. In so doing, a systematics of the O(+) intruder states and of the level density of nuclear states for Pb (where a shell closure effect is expected) and for Cd (where a change in the pairing force due to n-p interaction is expected) are studied. These examples show that the deviation of the level density parameter from the base line can be interpreted as a degree of clustering in a nucleus.

Additional information

Authors: ROHR G, JRC Geel, B-2440 Geel (BE)
Bibliographic Reference: Paper presented: Specialists' Meeting on Nuclear Level Densities, Bologna (IT), Nov. 13-17, 1989
Availability: Text not available
Record Number: 198911234 / Last updated on: 1994-12-01
Original language: en
Available languages: en