Time Dependence of Resonance γ‐Radiation Modulated by Acoustic Excitations. Experiment

Abstract

Investigations of the time dependence of the r-resonance absorption line intensity in c a s e of modulation by acoustic waves occupy a special place i n modulation Mossbauer spectroscopy. The first works in that field performed by Perlow and Monahan and Perlow /1, 2/ correspond to the case when the acoustic oscillation frequency is g r e a t e r than the absorption linewidth ra. In those papers the counting rate of ;r-quanta is shown to become dependent on time due t o the transition of the r-radiation frequency modulated by the source oscillations through the crystal. Harmonic composition and relative phase of the counting rate are sensitive t o small shifts of energy and may be used t o measure them. Paper /3/ reports lineshapes in Mossbauer experiments with sinusoidal phase modulation at frequencies close to the linewidth of the Mossbauer state.The present note suggests an experimental realization of the case considered in /4/ where the authors theoretically analysed the time-dependent Mossbauer spectroscopy when r-radiation was modulated by low-frequency acoustic oscillations (Wr).In our experiment the source of the resonant -6-quanta was 57C0 in a chromium matrix and a stainless steel foil 10 prn thick was chosen as an abs o r b e r . The block diagram of the experimental device is presented in Fig. 1.The r-radiation passes through the oscillating absorber 1 and is registered by the multichannel analyser 4 operating in a multiscalar.mode. The absorber is oscillated by the vibrosystem 2 supplied by a periodical voltage from the sound generator 5. The s a m e generator simultaneously excites circuit 6 which forms the starting pulse from each period t o start the internal sweep of the analyser channels.1) Hr. Nersesyan s t r . 25, 37501 4 Erevan, USSR.

Effect of Forced Vibrations on the Scattering of X‐Rays and Mössbauer Radiation by a Crystal (I)

“…The coherent and noncoherent approaches were combined in [8,9]. At first the influence of coherent ultrasonic waves on the Mossbauer absorption spectrum has been observed in [lo,111. Paper [12] is devoted to the inverse problem for the case of low-frequency modulation.…”