Effect of Pressure on the Decay Constant ofTc99m

Abstract

An experimental investigation of the influence of high hydrostatic pressure on the decay constant of ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ has been performed. By the use of a multianvil high-pressure apparatus, a carrier-free source of ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ was compressed at a pressure of 100 kbar. The observed decay rate of the compressed ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ source was compared with that of a standard ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ source in the normal uncompressed state. The fractional increase in the decay constant, $\frac{\Delta \lambda }{\lambda }$, of the compressed ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ under that pressure was found to be (4.6 ± 2.3) × ${10}^{-4\mathrm{}}$. Our result agrees with that observed by Bainbridge, $\frac{\Delta \lambda }{\lambda }=(2.3\mathrm{}\pm 0.5)\times {10}^{-4\mathrm{}}$, to within a factor of about 2. Comparison with theoretical studies by other workers is also discussed.