Knowledge Bank

The modulation of low temperature ($2\circ K$) molecular crystal fluorescence and phosphorescence by sub-microsecond duration heat pulses is discussed in connection with the study of rates of triplet energy transfer and trap thermalization. A discussion of the dynamics of heat pulse propagation in molecular solids is presented and estimates of the thermal relaxation time of the lattice obtained. It is suggested that these times are sufficiently short to permit investigation of the dynamics of exciton energy transport in molecular crystals by means of low temperature T-jump experiments. The details of the technique are discussed and results from several experiments presented. Additionally, heat pulse modulation of the electron paramagnetic spin distribution of radiative triplet states is discussed and some preliminary results presented.