Measurement and rate law analysis of D2 Q-branch line broadening coefficients for collisions with D2, He, Ar, H2, and CH4

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Abstract
Continuous‐wave stimulated Raman spectroscopy has been used to obtain high resolution vibrational Q‐branch spectra at room temperature for pure D2 and D2:He, D2:H2, D2:Ar, and D2:CH4 mixtures. Measurements have been made for J=0–5 in the density region of 0.5–20.0 amagat, from which line broadening coefficients have been determined. These coefficients have been analyzed using a modified exponential energy gap rate law to identify the contributions of rotationally inelastic collisions and vibrational dephasing collisions to the linewidth. This analysis has assumed that vibrational dephasing is independent of rotational state, in accord with available theoretical studies. Results are compared with experimental and theoretical work on H2, HD, and D2, thereby characterizing the contributions of rotationally inelastic and vibrational dephasing collisions to the line broadening coefficients as a function of both rotational level and collision partner.