Effect of Radio-Frequency Fields on Mössbauer Spectra

Abstract

The effect of a radio-frequency field on Mössbauer spectra is reconsidered. Both the ground and the excited state of the source nuclei are simultaneously exposed to the rf magnetic field. As an example, the effect of the rf field on ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nuclei in a source with magnetic splitting (detected by a single-line absorber) is discussed in detail for two experimental geometries. Mössbauer spectra taken at a constant velocity, but with varying radio frequency, show that the main features can be understood in terms of two-quantum processes (rf-induced transitions between the magnetic sublevels preceding or subsequent to the emission of a $\gamma$ quantum), as long as the rf amplitude is small compared to the static magnetic field at the nucleus.