Lifetime measurements have been made in the neutron-deficient nucleus ${}^{109}$Te using the coincident recoil distance Doppler-shift method. The experimental $B\left(E2\right)$ values have been compared with state-of-the-art shell-model calculations using the monopole-corrected realistic charge-dependent Bonn nucleon-nucleon potential. Lifetimes in the $\nu h_{11/2}$ band are consistent with an interpretation based on the deformation driving properties of a single valence neutron outside of the even-even tellurium core and highlight the unexpected presence of collective behavior as the $N=50$ shell closure is approached. Lifetime measurements for the low-lying positive-parity states also appear to correlate well with shell-model calculations. In addition, a comparison with the proton-unbound nucleus ${}^{109}$I suggests that the presence of a single decoupled valence proton affects the total measured $B\left(E2\right)$ strengths in a manner that is not currently well understood.

• Received 2 August 2012

DOI:https://doi.org/10.1103/PhysRevC.86.034308