Alpha Decay ofAm240

Abstract

Three $\alpha$ groups have been observed in the decay of the odd-odd nucleus ${}_{}{}^{240}{}_{}{}^{}\mathrm{Am}$ with energies and relative abundances of 5.378 (86.8%), 5.337 (12.0%), and 5.286 (1.23%) MeV. The branching ratio for these three $\alpha$ groups is 1.9×${10}^{-4\mathrm{}}$%. The ground state of ${}_{}{}^{240}{}_{}{}^{}\mathrm{Am}$ has spin and $K$ of 3, and odd parity. It is composed of proton and neutron quasiparticle states with Nilsson assignments ($K\pi \left[N{n}_z\Lambda \right]$) of $\frac{5}{2}$-[523] and ½+ [631], respectively. The most abundant $\alpha$ group is nearly unhindered, and hence the state it populates in ${}_{}{}^{236}{}_{}{}^{}\mathrm{Np}$ has the same configuration as the parent.