Pressure-Broadened Linewidths in the Electric-Field-Induced Spectrum ofH2

Abstract

The linewidths of $Q\left(0\right)-Q\left(4\right)\mathrm{}$ in the electric-field-induced fundamental band of ${\mathrm{H}}_2$ are measured with 0.027-${\mathrm{cm}}^{-1\mathrm{}}$ resolution for pressures between 4.4 and 35 atm. The widths are found to vary linearly with density, with negligible contributions from the Doppler effect because of collision narrowing. The values obtained for the broadening coefficients at 300°K are, in order of increasing $J$: 2.78, 1.83, 3.05, 4.60, and 3.26 in units of ${10}^{-3\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$/amagat. These values are 20-30% larger than previous results from Raman data. The linewidth calculations of Van Kranendonk are revised to include the effective rotational constants of ${\mathrm{H}}_2$, and the results are compared with experiment. The agreement is fair when the anomalously small calculated width for $Q\left(1\right)\mathrm{}$ is excluded.