Identification and decay of the 0.48 ms13/2+isomer inHg181

Abstract

A new isomer with a half-life of $0.48(2)$ ms was identified in the nuclide $^{181}\mathrm{Hg}$, which was produced in the complete fusion reaction $^{40}\mathrm{Ca}+^{144}\mathrm{Sm}\ensuremath{\rightarrow}^{184}\mathrm{Pb}$${}^{*}$ at the velocity filter SHIP (GSI, Darmstadt). The isomeric state was tentatively assigned a spin-parity of $13/{2}^{+}$. We propose that this isomer de-excites by a yet unobserved low-energy, strongly converted $\ensuremath{\gamma}$-ray transition, followed by a newly identified cascade composed of a $90.3$ keV $M1$ and a $71.4$ keV $E2$ $\ensuremath{\gamma}$-ray transition.