<title>Phonon spectroscopy and phonon-induced energy transfer in solids</title>

Abstract

We describe how defect induced one phonon absorption of far infrared radiation can be utilized for monochromatic generation of high frequency acoustic phonons in doped insulating materials. By combining this monochromatic phonon generation technique with an absorption vibronic sideband spectrometer we have been able to use time resolved high resolution phonon spectroscopy to investigate a range of fundamental dynamical processes which determine the behavior of a nonequilibrium phonon population. The combination of spectral and temporal resolution has enabled us to investigate the interaction of phonons both with electronic states and with themselves. We describe the mechanisms of energy transfer in insulating materials with particular emphasis on phonon assisted processes. While phonon assisted transfer is usually studied in a regime where a steady state phonon population stimulates energy transfer we describe results where a nonequilibrium phonon population stimulates the energy transfer between disparate Pr<SUP>3+</SUP> sites in PrF<SUB>3</SUB>.