Chemically induced change in nuclear decay rate as a tool for calibratingFe57isomer shifts

The calibration constant of ${\mathrm{Fe}}^{57}$ has been determined to be $\frac{\delta R}{R}=-\left({2.3}_{-0.8\mathrm{}}^{+2.6\mathrm{}}\right)\times {10}^{-4\mathrm{}}$, from the isomeric chemical shift of the 14.4-keV $\gamma$ rays, resulting from decay of ${\mathrm{Co}}^{57}$ diffused into zinc and vanadium host lattices. The difference in electron density at the nucleus was obtained directly from the measured difference in decay constant of the isomeric level. The fractional difference in the decay constant of the Mössbauer level of ${\mathrm{Fe}}^{57}$ between zinc and vanadium was measured to be (4.2 ± 2.2) × ${10}^{-4\mathrm{}}$.