Gamma Rays from the Hg199(n, γ)Hg200 Reaction and Energy Levels in Hg200

Abstract

$\gamma$-radiation from slow-neutron capture in ${\mathrm{Hg}}^{199}$ has been measured in the energy region from 150 to 8040 keV with a Ge(Li) spectrometer at the Brookhaven graphite reactor. The $\gamma$ energies have been obtained with an accuracy varying between 0.10 keV for intense transitions and 3.0 keV for very weak transitions. $\gamma$ radiation from resonance neutron capture has been measured between 5240 and 8040 keV. Altogether, 32 excited states in ${\mathrm{Hg}}^{200}$ are established, and their modes of decay are given. The lowest five levels have properties which are more complex than those predicted by the vibrational model. The neutron separation energy of ${\mathrm{Hg}}^{200}$ has been determined as 8028.8±0.5 keV. The neutron separation energy of ${\mathrm{Hg}}^{202}$ is 7755.1±1.5 keV.