Low-temperature dynamics in an ethanol glass studied by the long-lived stimulated photon echo

The long-lived stimulated photon echo has been used to measure the dynamics of a deuterated ethanol glass at 1.5 K. The time dependence of the effective dephasing time constant can be described by using the standard two-level system model and a I/R distribution function for the relaxation rates of the two level systems, except for the kHz-MHz region where a gap exists. The standard TLS model, however, does not describe correctly the longitudinal decay of the stimulated photon echo during the waiting time.