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The intent of the work reported here has been to ascertain which properties of nuclei with 20

A procedure is developed to calculate the chemical potential of a system of fermions at high temperatures in the independent particle model. This is then used to investigate the occurrence of liquid-gas phase transitions in finite nuclei employing various zero-range nuclear effective interactions. Finite size effects and the Coulomb force are found to lead to a sizeable reduction in the "critical" temperature as compared to the case of infinite nuclear rnatter.

The g 9/2 shell of identical particles is the first one for which one can have seniority-mixing effects. We consider three interactions: a delta interaction that conserves seniority, a quadrupolequadrupole (Q·Q) interaction that does not, and a third one consisting of two-body matrix elements taken from experiment ( 98 Cd) that also leads to some seniority mixing. We deal with proton holes relative to a Z = 50, N = 50 core. One surprising result is that, for a four-particle system with total angular momentum I = 4, there is one state with seniority v = 4 that is an eigenstate of any two-body interaction-seniority conserving or not. The other two states are mixtures of v = 2 and v = 4 for the seniority-mixing interactions. The same thing holds true for I = 6. Another point of interest is that, in the single-j-shell approximation, the splittings ∆E = E(I max ) − E(I min ) are the same for three and five particles with a seniority conserving interaction (a well known result), but are equal and opposite for a Q · Q interaction. We also fit the spectra with a combination of the delta and Q · Q interactions. The Z = 40, N = 40 core plus g 9/2 neutrons (Zr isotopes) is also considered, although it is recognized that the core is deformed. PACS numbers:

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