DEPHASING OF OPTICAL EXCITATIONS IN DISORDERED ORGANIC $SOLIDS^{*}$

$^{*}$Supported by Air Force Office of Scientific Research, Contact \# F49620-79-C-0229 $^{+}$ Alfred P. Sloan FellowAuthor Institution:In a disordered solid the dephasing is induced by both the disorder and the physical processes leading to $T_{1}$ and $T_{2}$-relaxation. This paper presents results of investigations on dephasing of optical excitation in disordered solids by measuring the temperature dependence of the linewidth and lineshape. Several types of optical excitations (electronic, internal vibration and phonon) in both structurally and substitutionally disordered solids are investigated. Vibrational excitations are studied in the Raman spectra while the study of electronic excitations employs absorption and emission spectra. Computer simulation methods are used to compare the experimental observations with the theoretical models of dephasing in order to identify the $T_{1}$ and $T_{2}$ relaxations involved