Effect Of A Triaxial Nuclear Shape On Proton Tunneling: The Decay And Structure Of Tm-145

Gamma rays deexciting states in the proton emitter Tm-145 were observed using the recoil-decay tagging method. The Tm-145 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 Er-144 and the 2(+)-> 0(+) 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 pi h(11/2) band and the proton-decay rates in Tm-145 are consistent with the presence of triaxiality with an asymmetry parameter gamma approximate to 20 degrees.