High spin states of ${}^{204}$At: isomeric states and shears band structure

Abstract

High-spin states of neutron deficient Trans-Lead nucleus ${}^{204}$At were populated up to $\sim 8\mathrm{MeV}$ excitation through the ${}^{12}$C + ${}^{197}$Au fusion evaporation reaction. Decay of the associated levels through prompt and delayed ${\hat{I}}^3$-ray emissions were studied to evaluate the underlying nuclear structure. The level scheme, which was partly known, was extended further. An isomeric $16^{+}$ level with observed lifetime $\ddot{I}„=52\pm 5\mathrm{ns}$, was established from our measurements. Attempts were made to interpret the excited states based on multi quasiparticle and hole structures involving $2f_{5/2}$, $1h_{9/2}$, and $1i_{13/2}$ shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~$16^{+}-23^{+}$ was confirmed and evaluated in more detail, including the missing cross-over $E2$ transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighbouring neutron deficient ${}^{202}$Bi, ${}^{205}$Rn isotones and the ${}^{203}$At isotope. Based on comparison of the measured $B(M1)/B(E2)$ values for transitions along the band with the semiclassical model based estimates, the shears band of ${}^{204}$At was established along with the level scheme.

This preprint has not undergone peer review or any post-submission improvements or corrections. The Version of Record of this article is published in The European Physical Journal A and is available online at https://doi.org/10.1140/epja/s10050-022-00809-4