Yrast traps and very high spin states in the N approx. 82 region

The properties of discrete high-spin states at or near the yrast line are discussed. A possible general relation between the energies and spins of yrast states and the question of whether shape changes are induced by large angular momentum are considered. The emphasis is on particle alignment along a symmetry axis. The yrast lines expected from different modes of motion are shown. High-spin isomers found in bombardment of Sn and Te by 32S are tabulated. The occurrence of high-spin isomers provides a valuable experimental tool for studying by delayed coincidence methods states of even higher spin, which eventually decay into the isomer; use of this technique is described. Spectra from the 124Sn (32S, xn) reaction are shown, and detailed level schemes (J, π, multipolarity, lifetime) are presented for 151Dy and 152Dy. Plots of energy vs I(I+1) are given and interpreted for these nuclei. 13 figures, 1 table