Strong M1 components in 3(i)(-) -> 3(1)(-) transitions in nearly spherical nuclei: Evidence for isovector-octupole excitations

An evaluation of data obtained in (n, n'gamma) experiments reveals strong M1 3(i)(-) -> 3(1)(-) transitions in nuclei near the N = 50 (Zr-92, Mo-94, and Mo-96), Z = 50 (Cd-112 and Cd-114), and N = 82 (Nd-144) shell closures. The observed < 3(1)(-) ||M1||3(i)(-)> matrix elements scale with the < 2(1)(+) ||M1||2(ms)(+)> matrix elements connecting the mixed-symmetric and symmetric quadrupole excitations. In accordance with a picture of a mixed two-component quantum system, the energy difference between the initial 3(i)(-) state and the 3(1)(-) octupole phonon is proportional to the |< 3(1)(-)|| E3||0(gs)(+)>| matrix element. The possibility of assigning the 3(-) states of interest as octupole isovector states is discussed.