EVIDENCE FOR HEXADECAPOLE COLLECTIVITY IN CLOSED-SHELL NUCLEI

Evidence for hexadecapole collectivity in closed-shell nuclei is presented by examining the observed characteristics of the lowest 4+ excited state in each case. These 4+ states, presently identified in the N=82 isotones Sn132 and Ce140, and the Z=82 isotopes, Pb202 and Pb204, have nanosecond half-lives, and are found to decay by enhanced E4 transitions to the respective 0+ ground state, whereas ΔI=2 E2 transitions from, and to, these states have B(E2) values which are only a fraction of a Weisskopf unit. These features, suggestive of a significant one-phonon hexadecapole component in the structure of these 4+ states, are interpreted in terms of their shell model configurations. Similar characteristics are predicted for some other closed-shell nuclei. © 1995 The American Physical Society.