Hydrogen and helium pressure broadening of water transitions in the 380– region

Abstract We present results of recent experiments on the pressure broadening of pure rotational transitions of H216O water in the 380– 600 cm −1 range by hydrogen and helium. The hydrogen coefficients vary between 0.033 and 0.076 cm −1 / atm (average: 0.056 cm −1 / atm ) while the helium coefficients vary between 0.006 and 0.017 cm −1 / atm (average: 0.013 cm −1 / atm ) . While this average hydrogen-broadening coefficient matches the average nitrogen-broadening coefficient we observed in this region earlier, the range over which they vary is narrower for hydrogen than for nitrogen. We find that previously published complex Robert–Bonamy formalism calculations of the hydrogen coefficients are broadly consistent with these results, and that, to some extent, our experimental results can be predicted from HITRAN air widths.

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