Single molecule spectral trajectories in low-temperature glasses

Spectral jumps of single molecule line shapes in low-temperature glasses are associated with tunneling of slow two-level systems. Each spectral trajectory can be characterized by its frequency autocorrelation function, which differs from molecule to molecule. We examine theoretically the distributions of the zero-time values and certain moments of the autocorrelation function. Based on the standard assumptions of two-level systems that are distributed homogeneously in space, and have dipolar interactions with the chromophore, we find that these distributions all map onto the same master curve. This theoretical prediction is proposed as a test of the above assumptions.