Anomalous impurity spectra in low-temperature glasses

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Abstract
Spectral holes have been measured for chlorin dopant educt and photoproduct states in five different glasses, o-terphenyl, benzophenone, polystyrene, ethanol, and triethylamine at 5 K. In contrast to the conventional picture of zero-phonon holes and phonon sideholes observable in the educt state, spectral holes in the photoproduct state reveal rather unconventional features. No zero-phonon hole is observable yet the spectra exhibit a peculiarity resonant with the burning frequency (‘‘Λ-spectra’’). The low-temperature vibronic spectra of an impurity in a 1D elastic lattice are calculated and demonstrated to match qualitatively well the Λ-spectra in the case of weak electron-phonon coupling. The applicability of a 1D model is argued to be due to the formation of a local structural defect (planar crack) caused by dopant phototransformation.