Lifetimes andg-factor measurements in the decay of the 399 keV isomeric state inPt197and the quasiparticle-phonon coupling model

The nuclear levels in ${}_{}{}^{197}{}_{}{}^{}\mathrm{Pt}$ have been studied from the decay of 95.4 min ${}_{}{}^{197}{}_{}{}^{}\mathrm{Pt}_{}^m{}_{}{}^{}$. The isomeric state was produced by ($n$,$\gamma$) reaction on the enriched ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pt}$. The $\gamma$-ray spectra have been observed with a hyperpure Ge detector and a large volume Ge(Li) detector. The half-lives of the 399 keV and the 53 keV states were determined with improved precision. The results are $T_{\frac{1}{2}}$ (399 keV) =95.41±0.18 min and $T_{\frac{1}{2}}$ (53 keV)=16.58±0.17 ns. The $g$ factor of the 53 keV ${\frac{5}{2}}^{-}$ state has been measured by the gamma-gamma time differential perturbed angular correlation method in an external magnetic field of 25.1 kG using the 346-53 keV gamma cascade. The value of the $g$ factor was obtained to be +0.335±0.010. This result is compared with the known $g$ factors of the similar states in ${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$, and in ${}_{}{}^{197}{}_{}{}^{}\mathrm{Hg}$ and ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$, and also with theoretical calculations based on the quasiparticle-phonon coupling scheme. The possibility of using the 346-53 keV gamma cascade in ${}_{}{}^{197}{}_{}{}^{}\mathrm{Pt}$ in the future time differential perturbed angular correlation studies is discussed.