Moessbauer spectra of interacting fine particles

Exact formulae for the Moessbauer absorption spectra are derived on the basis of the dispersion theory, for solid absorbers as well as for systems of interacting fine particles. The result shows that the spectra consist of a great many Lorentzian lines of natural width. These lines are classified into several groups according to the categories of the vibrational modes in the absorber, to which the lines are related, each group constituting a spectral component. In particular, for the systems of interacting fine particles, a component due to particle-oscillation modes can be observed under some conditions in the Moessbauer spectra as broad lines superimposed on the usual unshifted narrow lines. (orig.)