Determination of Zero-Point Phonon Parameters: Calibration of the Second-Order Doppler Shift
A considerable body of research has been devoted to the determination of the Mössbauer recoil-free fraction, or f-factor, from which the mean square atomic displacement of resonant nuclei can be deduced. A quantity intimately related to the mean square displacement, but considerably less accessible to experiment, is the mean square velocity. Normally this quantity is hidden amida wealth of complexity relating to the chemical shifts of source and absorber. We have developed a technique of inter comparing two quantities, both directly determined from the Mössbauer experiments—the recoil-free fraction and the second order Doppler shift—so as to permit deduction of the absolute zero-point mean-square velocity. This quantity has not been hitherto determined in any experiments of which we are aware, and we believe it will prove valuable in permitting tests of theoretical models of impurities in crystal lattices. Results are presented for a number of systems involving both the Fe57 and the Sn119 resonances.
KeywordsDebye Model Einstein Model Resonant Nucleus Mossbauer Effect Order Doppler Shift
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