Double Isomerism inAs73

Abstract

The levels in ${\mathrm{As}}^{73}$, populated by the decay of ${\mathrm{Se}}^{73}$, were studied. States at 0.425 and 0.066 MeV were found to decay by means of two cascade gamma rays with energies of 0.359 and 0.066 MeV, with no observed crossover transition. Half-lives of 5.0±0.4 μsec and 6.1±0.4 nsec were measured for the 0.425- and 0.066-MeV states, respectively. The 0.066-MeV transition, previously assigned as $M1\mathrm{}$, was found to be retarded by a factor of 97 compared to single-particle estimates. This result tends to confirm the $l$-forbidden character of this transition. This retardation is compared with that for the 0.068-MeV transition in ${\mathrm{Ni}}^{61}$, which proceeds between analogous states.