The recently discovered, magnetically induced radio-frequency sidebands in the Mössbauer spectrum of metallic iron1 have been studied in more detail. Results of a survey to determine sideband intensity and location as a function of the experimental parameters are reported. In the earlier work1 the relative sideband intensities were fitted using Bessel functions Jn2(m), assuming that all the nuclei were vibrating with similar amplitudes. If, however, one assumes a Rayleigh distribution of amplitudes, the relative intensities should be proportional to exp(-m2)In(m2).2 A closer examination of the spectra indicates that either of these functions fits the data fairly well, although some intermediate distribution would seem to be more appropriate, particularly in light of a more elaborate model3 which relates the two functions cited above to sideband intensities at opposite extremes of phonon relaxation time (i.e., the time for a monochromatic vibration to spread into a wave packet characterized by kT). It should be stressed that fitting the data to either function yields essentially the same values for the physical parameters. Our original experiment1 was performed without a static field. When a static field is applied such that the rf field H 1, the static field H0, and the plane of the absorber foil are mutually perpendicular, the presence of H0 has little effect on the sideband intensity for values of H0 up to 1 kG. Above 1 kG, the sideband intensity rapidly diminishes, falling to zero at H0≈2 kG. When H0 is oriented parallel to H1, we find that the sideband intensity diminishes rapidly, even for small fields (H 0≈50 G), although a small sideband effect persists for fields as high as 1 kG. © 1969 The American Institute of Physics.
