On the Experimental Identification of Spin-Parities and Single-Particle Configurations in $^{257}$No and Its $\alpha$-Decay Daughter $^{253}$Fm

Abstract

Recently measured lifetimes of the favored $\alpha$ decays from $^{257}$No have been calculated using the quantum mechanical tunneling within WKB approximation using microscopic nuclear potentials. Results obtained assuming previously assigned (ambiguous) parent spin of $\frac{7^+}{2}$ and newly assigned configuration $\frac{3^+}{2}$ [622] have been compared. Hindrance factors for the favored decays have also been compared with the calculated hindrances using higher angular momenta transfers. Although the calculations substantiate the findings, yet it makes the spin-parity assignment of $\frac{3^+}{2}$ for the ground state of $^{257}$No less definite.