First observation of proton emission from deformed states in ^140Ho and ^141mHo^*

New proton emitters, ^140Ho and ^141mHo, located in the region of deformed nuclei were identified at HRIBF (ORNL) using a fusion--evaporation reaction of a ^54Fe beam (315 MeV) on a ^92Mo target (0.91 mg/cm^2). Reaction products were selected by means of the Recoil Mass Spectrometer and identified with the Position Sensitive Avalanche Counter and Double-Sided Silicon Strip Detector. The known proton emitter ^141gsHo (E_p=1.17 MeV, T_1/2 ≈ 4 ms) as well as two new proton radioactivities were detected. Position correlations allowed us to separate the proton activities at A=141 and A=140. A new proton line at A=141 (preliminary values of E_p=1.23(2)MeV and T_1/2 ≈ 10 μs) was assigned to the decay of ^141mHo. Measured decay properties and the calculations including minimization of total energy surface with respect to [β_2,β_4,β_6] deformation space suggest 7/2^-[523] and 1/2^+[411] proton orbitals for the configurations of ^141gsHo and ^141mHo, respectively. The proton line correlated with the implantation of A=140 recoils (preliminary values of E_p=1.086(10) MeV and T_1/2 ≈ 6 ms) was assigned to the decay of ^140gsHo. The structure of this odd--odd emitter could be described as a coupling of 7/2^-[523] proton to the 7/2^-[514] or 5/2^+[402] neutron orbital, since these two configurations are predicted to be nearly degenerate. ^* Work supported by the U.S. Department of Energy.