Recoil-Free Resonant Absorption inAu197

Abstract

The Mössbauer absorption in Au has been measured at 4°K for the 77-kev gamma ray emitted by ${\mathrm{Au}}^{197}$ nuclei embedded in gold, platinum, stainless steel, iron, cobalt, and nickel. In each case, a Doppler-shift curve was measured to find the effective width and the chemical shift. The recoil-free fractions, $f$, are obtained with the aid of a straightforward analysis, which incidentally shows the errors that can be made in $f$ if the chemical shift and effective width are not taken into account. The observed recoil-free emission fractions were found to be approximately 0.06 (Au), 0.34 and 0.14 (Pt), 0.24 (steel), 0.32 (Fe), 0.27 (Co), and 0.35 (Ni). The relative $f$ values are correct; the correct absolute $f$ values might require a multiplicative correction factor that could be as small as 0.53.