Knowledge Bank

Temperature dependence of linewidths, lineshapes and frequencies can be used to derive the mechanism of dephasing and rates of vibrational relaxation [$T2$-relaxation). Experimental results are presented for Raman active phonons as well as for internal vibrations in several organic crystals and crystalline complexes. The effects on vibrational dephasing due to excitation delocalization as well as due to a dense manifold of vibrational states in the environment of a crystalline complex are investigated. A theoretical discussion is presented. From a correlation between the theoretical prediction and the experimental observation, the mechanism of dephasing is identified.