The dynamics of formation of self-trapped excitons and Frenkel pairs, upon band-gap excitation, were studied by means of fs time-resolved spectroscopy at 6 to 330K. It was found that the primary yield of Frenkel pairs was governed by a process of exciton relaxation that ended within 10ps of excitation at all of the temperatures studied. The yield increased with temperature, and was anti-correlated with the yield of triplet self-trapped excitons. This revealed a strong effect of temperature upon branching during exciton relaxation.

Temperature-Dependent Yield of Frenkel Pairs Generated by Valence Excitation in NaCl. K.Tanimura, W.P.Hess: Physical Review B, 2004, 69[15], 155102 (7pp)