Effect of a triaxial nuclear shape on proton tunneling: the decay and structure of 145Tm.

Gamma rays deexciting states in the proton emitter $^{145}\mathrm{Tm}$ were observed using the recoil-decay tagging method. The $^{145}\mathrm{Tm}$ ground-state rotational band was found to exhibit the properties expected for an ${h}_{11/2}$ proton decoupled band. In addition, coincidences between protons feeding the ${2}^{+}$ state in $^{144}\mathrm{Er}$ and the ${2}^{+}\ensuremath{\rightarrow}{0}^{+}$ $\ensuremath{\gamma}$-ray transition were detected, the first measurement of this kind, leading to a more precise value for the ${2}^{+}$ excitation energy of 329(1) keV. Calculations with the particle-rotor model and the core quasiparticle coupling model indicate that the properties of the $\ensuremath{\pi}{h}_{11/2}$ band and the proton-decay rates in $^{145}\mathrm{Tm}$ are consistent with the presence of triaxiality with an asymmetry parameter $\ensuremath{\gamma}\ensuremath{\approx}20\ifmmode^\circ\else\textdegree\fi{}$.