Temperature broadening of impurity transitions in the crystalline and glassy phase of benzophenone

The temperature dependence of the width of spectral holes in the crystalline and glassy phase of benzophenone:chlorin solid solutions is measured between 1.5 and 10 K. In the crystal, the holewidth levels on Γ(0) = 45 MHz for T < 5 K. This is close to the lifetime-limited value. For T > 5 K, it exhibits a rapid increase. In the glassy phase, the holewidth exceeds that in the crystalline state by more than a factor of ten. For T < 4 K, the width is governed by a power law with an exponent of 1.28. Around 5 K, there is a clear onset of a much steeper dependence.