NUCLEON-PAIR SHELL-MODEL - THE EFFECTS OF THE SD PAIR STRUCTURE ON COLLECTIVITY OF LOW-LYING STATES

In the nucleon-pair shell model truncated to the S-D subspace with sin gle-particle level splitting fully taken into account, the effects on the collectivity due to the pair structure are studied for Ba-134. It is found that the yrast states are not sensitive, but the others, espe cially the 0(2)(+) and 2(2)(+) states, are very sensitive to the D-pai r structure. Among the four pair structures studied in the paper, only the SD pairs taken from the 0(1)(+), 2(1)(+) states of two-valence-nu cleon systems with surface delta interaction can describe the spectra, and the B(E2) and B(M1) values of Ba-134. (C) 1998 Published by Elsev ier Science B.V.