Application of the Mössbauer effect to the study of opto‐acoustic phenomena

Abstract

We present the results of the proof of principle experiment on the observation of the acoustic oscillations induced by the pulsed laser excitation. Time domain spectra agree well with the model of the frequency modulation of Mössbauer radiation passing through a vibrating resonance medium. The ratio of the fourth and second Fourier harmonics D 4V =D 2V of the modulated radiation is suggested to measure the modulation index since this ratio is very sensitive to the amplitude of nuclear vibrations. The proposed methodology may be used for the study of opto-acoustic phenomena. 1 Introduction Mössbauer spectroscopy is a unique technique for investigating structural and dynamical properties of solids on the atomic scale. This technique provides information about local symmetry, magnetic ordering, and chemical bonding in the immediate vicinity of the probing nucleus. Among many other promising applications of Mössbauer effect there are those, which provide information about dynamical processes induced in materials by radiofrequency (RF) magnetic field, ultrasound, and optical laser radiation [1]. Since the discovery of the Mössbauer effect a number of interesting phenomena stimulated by external fields were observed: Ultrasonic [2] and magnetostriction modulation of gamma-radiation [3][4][5], RF collapse of the magnetic hyperfine structure [6], Rabi splitting of Mössbauer lines under NMR excitation [7][8][9], the effect of the rotating hyperfine magnetic field [10], gamma echo [11], etc. These phenomena noticeably enhance the efficiency of the Mössbauer effect as an experimental tool and allow getting information not attainable by conventional acquisition schemes. For example, the modulation of Mössbauer spectra with ultrasound was efficiently used in studies of ultrasonic phenomena in solids [12]; RF collapse of the magnetic hyperfine structure was used in magnetic soft alloys for determination of the quadrupole splitting distribution [13]; Rabi splitting of Mössbauer lines were used to determine the amplitude of the RF field experienced by a nucleus and the hyperfine amplification factor [14].

Application of the Mössbauer effect to the study of subnanometer harmonic displacements in thin solids

“…Similar experiments were performed with the vibrated absorber and the source moved only by Mössbauer drive [10,18,19,25]. In…”

“…In addition to the arguments given above, the incoherent model contradicts the observations of time domain spectra, which are obtained for γ rays from the vibrated source by filtering trough a single line absorber [8,9]. Similar experiments were performed with the vibrated absorber and the source moved only by Mössbauer drive [14,15,20,21]. In Ref.…”

“…Among them, we just briefly mention a few. They are gravitational red shift experiments [1][2][3][4][5][6][7], novel tests of the general relativity theory [8,9], detection of fast and tiny sample displacements induced by pulsed-laser heating [10], time differential nuclear resonance spectroscopy of geophysically important materials containing iron under extremely high static pressure and pulsed laser heating, which simulate physical and chemical processes in deep planetary interiors [11]. A rapidly developing field of science, which is known as γ-ray (or hard x-ray) quantum optics based on Mössbauer effect, provides unambiguous test of many concepts and ideas of coherent quantum optics with γ-photons resonantly interacting with ensemble of nuclei.…”

Transmission of gamma-quanta through vibrating target

“…Combining (9) and 10 (13) The relation (13) can be called an addition 126 theorem for the expansion coefficients n a in close analogy with the theorem for Bessel functions [13].…”