Ethanol glass dynamics: Logarithmic line broadening and optically induced dephasing

The time and fluence dependence of the homogeneous line width of Zn-porphin in deuterated ethanol glass at 1.8 K is remeasured by stimulated photon ec ho. The observed spectral dynamics is interpreted in terms of the standard two-level system model and by using a commonly used modified version of it. It is shown, as was suggested recently (Phys. Rev. B 1997, 56, 11571), tha t time-dependent local heating is the cause of the plateau found in earlier echo experiments on this system. The anomalous intensity loss of the photo n echo in the population dimension, however, is confirmed, as well as the e xistence of excess optical dephasing on a short time scale. The former effe ct is attributed to spontaneous frequency jumps outside the laser bandwidth , the latter to spectral diffusion induced by the change of electronic stat e of the chromophore. This phenomenon is not captured in existing theoretic al models, which assume the probe molecule to be just a spectator of glass dynamics.