Photon correlation probing of spectral diffusion in impurity glasses

A method of photon correlation probing of spectral diffusion at ultralow temperatures is suggested for polymer glasses. The method makes it possible to determine the ensemble-averaged autocorrelation function of fluctuations in the spectra of individual chromophores from the fluctuations of the fluorescence intensity of a sample, as well as to select subensembles of impurity molecules by the amplitudes of spectral jumps of their absorption lines due to the transitions of molecules between equilibrium states closely spaced in energy. The method has a number of advantages in comparison with the conventional methods of investigation of spectral diffusion: single-molecule spectroscopy, hole-burning spectroscopy, and the measurement of hole broadening with time.