Search for the resonance environmental effect on the decay periods of long-lived nuclear isomers

Experiments on a search for the resonance environmental effect on the decay periods $T_{1/2}$ of long-lived nuclear isomers are described. It is shown that a change in $T_{1/2}$ obtained upon sample cooling in previous experiments with the $^{180m}$Hf isomer is likely due to the insufficient correctness of the procedure used for separating $\gamma$-peaks from the backgrounds in the measured $\gamma$-spectra. The new approach to this problem reveals the absence of this effect for $T_{1/2}$ within an experimental accuracy of 1.2%. However, a difference of $2.25\pm 0.77\%$ between the $^{103m}$Rh decay periods $T_{1/2}$ was found for the solid and liquid $\gamma$-sources. A control experiment with the $^{80m}$Br isomer showed that, as expected, the decay periods $T_{1/2}$ for two temperatures coincide with each other within an accuracy of 1%.