LINE MIXING AND STATE-TO-STATE ROTATIONAL RELAXATION RATES IN D2 DETERMINED FROM THE RAMAN Q-BRANCH

Precise line-shape measurements of the Q(0) to Q(4) lines in D2 have been made using Raman gain spectroscopy. At the densities studied (2.5-30 amagat), the Q-branch lines are well separated but slightly asymmetric due to quantum-mechanical line mixing. We have measured both the symmetric and the asymmetric contributions to the line shape as a function of the density. From the broadening coefficients and the line-mixing parameters, we have deduced the dephasing and the state-to-state rotational relaxation rates. Semiquantitatively, the results support the empirical modified-exponential-gap law.