Abstract

Recent experimental data show that the optical dephasing processes leading to zero-phonon lines (ZPL) temperature broadening in the spectra of impurity crystals result from quadratic electron-phonon interaction [1-4]. However, this theory fails to describe some of the experimental results [4]. We suppose that another mechanism of ZPL temperature broadening in crystal can exist. The experimental data presented in this paper show that the temperature broadening of ZPL is due to the low-frequency excitation of non-phonon type. They are excitations in so-called Two-Level Systems (TLS) [5,6], which are under discussion at present with respect to dephasing processes in polymers and glasses [2].

© 1992 Optical Society of America