On a Certain Inverse Problem in γ ‐Acoustic Spectroscopy

Abstract

Acoustic Spectroscopy Paper /1/ suggests a new method to measure the propagation velocity and attenuation coefficient of acoustic oscillations based on modulation of resonance 7-radiation by coherent ultrasonic excitations. To measure changes of the sound velocity in condensed media the investigated sample was placed in a special cell transmitting acoustic excitations from the transducer t o the absorber. Characteristic dependences of the unshifted line intensity of the Mossbauer absorption spectra on the sample thickness with olive oil a s medium a r e shown in Fig. 1. Here the unshifted absorption line intensity is seen t o oscillate depending on the layer thickness d. This is due to the change of amplitude of the acoustic wave /1/ which reaches the absorber and which has its maxima a t d = n h / 2 a n d i t s m i n i m a a t d = ( 2 n + l ) h / 4 , n = l , 2, ..., while h i s t h e sound wavelength. -On the other hand, propagation of acoustic waves in condensed media is accompanied by attenuation, the ultrasound amplitude decreasing and the central line intensity increasing with the increase of the thickness (see Fig. 2 ) . 0.8 1 '? 0.7 9 0.6 0.2 03 0.4 03 . d (mm) -* Fig. 1 . Dependence of the unshifted line relative intensity on thickness (olive oil). As shown in /2/, for the applied Mossbauer sample with the effective thickness B = 0.6the ratio of the peak square in case of US excitation to that without US may with great accuracy be replaced by the ratio of intensities 1 ) 375012 Erevan, USSR.