$K$-shell internal conversion coefficient for $M4$ decay of the 30.8 keV isomer in $^{93}\mathrm{Nb}$

$K$ -shell internal conversion coefficient for $M 4$ decay of the 30.8 keV isomer in ${}^{93}{Nb}$

V. Horvat, E. E. Tereshatov, J. C. Hardy, N. Nica, C. M. Folden, III, V. E. Iacob, and M. B. Trzhaskovskaya

Phys. Rev. C 102, 014310 – Published 13 July 2020

Abstract

The 30.8 keV ${(1 / 2)}^{-}$ isomeric state in ${}_{41}^{93}{Nb}$ decays by an $M 4$ transition to the ${(9 / 2)}^{+}$ ground state. We have measured the $K$ -shell internal conversion coefficient $α_{K}$ for this transition in order to test the validity of current methods of calculation for a case with relatively low atomic number, low transition energy, and a high value of $α_{K}$ . Taking the fluorescence yield of niobium to be 0.751(4), we obtain $α_{K} = 2.56 (9) \times 10^{4}$ , a result that agrees with the Dirac-Fock calculations that take into account the presence of a $K$ vacancy in the final state, and disagrees by 1.7 standard deviations with calculations that ignore the vacancy. We also determine the energy of the isomeric state to be 30.760(5) keV, a fourfold improvement in precision over the currently accepted value.