Investigation of the effect of resonant environment (Ms̈sbauer screen) on the observed half-life of the ${}^{119m1}$Sn isomer ($E=23.8$ keV, $T_{1/2}\sim18$ ns)

In order to analyze the effect of resиonant environment on the $\gamma$ decay of excited nuclei, the half-life of the${}^{119m1}$Sn isomer ($E=23.8$ keV, $T_{1/2}\sim18$ ns), which appears from the decay of the ${}^{119m2}$Sn state ($E\sim89$ keV, $T_{1/2}\sim293$ d), has been measured by the $e-\gamma$ coincidence method on samples consisting of the mixture of tin oxides containing the ${}^{119}$Sn stable nucleus and ${}^{119m2}$Sn radioactive nuclei with various values of the ${}^{119}\mathrm{SnO}_2/{}^{119m2}\mathrm{SnO}_2$ ratio. For the samples, where this ratio is equal to $6.2\times10^4$, $1.2\times10^6$, $6.5\times10^6$ and $1.7\times10^7$, the half-life $T_{1/2}$ is equal to 18.69(2), 18.71(2), 18.91(5), and 19.43(4) ns, respectively. For the reference sample (a metal with a ${}^{119}\mathrm{Sn}/{}^{119m2}\mathrm{Sn}$ ratio of $1.5\times10^5$, the value $T_{1/2}=18.68(6)$ ns is obtained.