Terrylene in hexadecane revisited: A hole burning study

Holes burnt into the absorption spectrum of terrylene in hexadecane have quite unusual features: spectral diffusion behavior under thermal cycles shows a narrowing regime at very low temperatures (2-5 K) followed by a plateau region (up to about 13 K) and a broadening regime (T13 K). Thermal line broadening (quasihomogeneous linewidth) shows a nonmonotonous behavior as a function of temperature: at around 4 K there is a maximum followed by a flat minimum and the onset of strong broadening at higher temperatures. Finally, the central hole shows one-sided narrowly spaced side features. This behavior is interpreted within the frame of a two-site model. One of the two sites can be well described by a standard two level system; the other, however, shows characteristic features of a multilevel system. The two sites are characterized by strongly different optical linewidths, phototransformation yields, and thermal stabilities.