DIRECT OBSERVATION OF RADIATIONLESS RELAXATION PROCESSES IN MOLECULAR CRYSTALS AT $2^{\circ} K$

Abstract

Experiments will be described in which ultra-sensitive, thin-film semiconductor detectors are utilized to detect heating in molecular solids generated by radiationless electronic relaxation processes. The relative importance of radiationless and radiative relaxation routes from $S_{1}$ and $S_{2}$ of solid biacetyl are discussed in terms of the experimental results. Time resolved measurements of the relative rates of electronic relaxation from the excited singlet states of solid biacetyl are also discussed. Heating effects on the order of several microdegrees Kelvin due to radiationless electronic relaxation and photochemical decomposition processes have been recorded and will be briefly discussed.