Mössbauer Method for Studying Vibrations in a Granular Medium Excited by Ultrasound

Abstract

It is shown that analysis of Mössbaur spectra of a granulated medium, immersed into the epoxy resin without hardener, allows to study mechanical vibrations of granules. In our experiments, small particles of the potassium ferrocyanide with a 1.25 micron mean size played a role of granules. This compound was enriched by 57 Fe isotope. Particle vibrations in the vibrated resin with the frequency 12.72 MHz were induced by piezo polymer film. At rest, Mössbauer spectrum of 57 Fe in the potassium ferrocyanide consists of a single line. Ultrasonic vibration of nuclei splits the line into a comb structure with a period equal to the vibration frequency. The spectrum analysis allows to estimate the vibration amplitude of particles and decay of the ultrasound in this medium.The proposed method is unique since it allows to measure subangstrom displacements of particles vibrating with several MHz frequency.

Powder vibration studied by Mössbauer spectroscopy

“…(2). Similar spectra were observed for powder pressed in a tablet onto the surface of piezo transducer [20] and powder suspended in viscous liquid or resin [22,27]. One may assume that grains in a pile or grains in a resin vibrate with the same frequency but their amplitudes are different depending on the distance from the transducer.…”

“…When the quasi-monochromatic source radiation with main frequency ω S is transmitted through a medium with resonant nuclei, which are vibrated, the spectrum of the radiation field is transformed into polychromatic with a set of spectral lines ω S ± nΩ, where Ω is the vibration frequency and n = 0, ±1, ±2 [20][21][22][23][24][25][26][27]. These lines are produced by Raman scattering, which is inelastic scattering of γ-radiation by vibrating nuclei.…”