We measured the Stokes to anti-Stokes intensity ratio in the phonon Raman spectrum of a rutile (TiO(2)) crystal. We found that although the ratio still equals the Boltzmann factor at the center frequency omega(0) of a mode, it deviates from the Boltzmann factor by up to 5% and approaches a constant value of e(h omega 0/kBT) within the spectrally-broadened region. It is suggested that irreversible dissipation is essential to understanding this deviation and the broadening of the phonon mode. (C) 2011 Published by Elsevier B. V.