Zero-phonon events

Recoil-free Fraction and Debye-Waller Factor We have already seen qualitatively that the recoil-free fraction or probability of zero-phonon events will depend on three things ... 

However, in contrast, the resonance effect increased by cooling both the source and the absorber. Mdssbauer not only observed this striking experimental effect that was not consistent with the prediction, but also presented an explanation that is based on zero-phonon processes associated with emission and absorption of y-rays in solids. Such events occur with a certain probability/, the recoil-free fraction of the nuclear transition (Sect. 2.4). Thus, the factor/is a measure of the recoilless nuclear absorption of y-radiation - the Mdssbauer effect. 

We apply Eq. (2.72) and obtain the weights of the phonon orders given in Table 2.7. Approximately 98% of the total intensity is found distributed across only the first three phonon orders. The zero-phonon line, or band origin, remains the strongest feature but, at this value of 0, the first order event is quite strong. If we had chosen 0 = 9 A, the first order contribution would have been the stronger. 

Figure 13.14 Evolution of a single QD continuous line is the fit obtained with our emission line as a function of temperature model. The inset shows the difference (empty dots same experimental data as between the zero-phonon line and the full Figure 13.13). The dotted line represents the model, which corresponds to the acoustic zero-phonon line (Voigt profile) and the phonon emission and absorption events.

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