Direct 2T1−2E Phonon Relaxation in Ruby and Its Effect Upon R-Line Breadth

Abstract
Fluorescence spectroscopy and R‐line excitation measurements have been made on ruby samples at 4°K. These demonstrate the existence of a direct relaxation process between the 2T1 and 2E levels—possibly by emission of a phonon into a mode affecting the trigonal component of the chromium ion site symmetry. It is shown that this process contributes a substantial part to the temperature‐dependent R‐line breadth in the range 100°–500°K.