Temperature dependence of the Raman linewidth and line shift for the Q(1) and Q(0) transitions in normal and para-H2

Abstract

Using stimulated Raman gain spectroscopy, we have measured the temperature and density dependence of the Raman linewidth and line shift for the Q(1) and Q(0) vibrational transitions in ${\mathrm{H}}_2$ covering the range 77–480 K and 1–20 amagats, and as a function of ortho to para ratio. We conclude that the dominant contribution to the Q(1) linewidth comes from vibrational dephasing collisions, an effect not included in current theories. The line-shift coefficient has a much larger temperature variation than the linewidth coefficient, with the ratio of line shift to linewidth reaching a maximum value of 7.3 at 81 K. These results are important for applications requiring the tuning of the Stokes frequency generated by the stimulated Raman process.