Effect of Pairing Correlations on Nuclear Gamma-Ray Transitions

Abstract

Several examples of the effect of pairing correlations on nuclear gamma- ray transitions are presented. It is shown that even it collective coupling exists, gamma-ray transitions of electric multipole type between low-lying quasiparticle states whose free shell-model orbit energies are symmetrically related to the Fermi energy may be extremely retirded. The factor (U/sub i/U/sub f/-V/sub i/V/sub f/) that arises fro m the pairing correlation is directly estimated from empirical even-odd mass difference data. The agreement of the calculated transition probabilities with experimental results is good. A shell- model calculation taking into account the pairing correlation was also made for transitions of E2 type between d/sub 3/2/ and s/sub 1/2/ orbits in Sn/sup 117/ and Sn/sup 11 8/ and the results are compared with that of the quasiparticle approximation. It is shown that the quasiparticle approximation is more improved by using renormalized wave functions that are obtained by projecting out only the terms having the correct number of particles than by taking into account only the blocking effect except for special cases. (auth)