Fragmentation of mixed-symmetry excitations in stable even-even tellurium nuclei

Abstract

The lowest six excited ${2}^{+}$ levels of the even-even $^{122\ensuremath{-}130}\mathrm{Te}$ nuclei have been investigated using \ensuremath{\gamma}-ray spectroscopy following inelastic neutron scattering. These levels have been identified and their decay properties have been characterized from \ensuremath{\gamma}-ray excitation functions and \ensuremath{\gamma}-ray angular distributions; additionally, lifetimes of these levels have been deduced using the Doppler-shift attenuation method. Electromagnetic transition rates and $E2/M1$ multipole mixing ratios from the ${2}_{x}^{+}[x=2\text{\ensuremath{-}}6]\ensuremath{\rightarrow}{2}_{1}^{+}$ transitions have been examined to identify the lowest mixed-symmetry states in these nuclei. In each nucleus, the mixed-symmetry strength appears to be fragmented between more than one level. The summed $M1$ strength from the ${2}_{x}^{+}$ [$x=2\text{\ensuremath{-}}6$] states to the ${2}_{1}^{+}$ level agrees rather well with neutron-proton interacting boson model predictions in the U(5) or O(6) limits for these Te nuclei.