Diode laser measurements of temperature-dependent line parameters for water vapor near 820 nm

Air- and self-broadening coefficients and relative line strengths for 8-10 low-J lines in the (2 1 1) vibrational band of water vapor have been accurately measured over the T = 330-540 K range using an 817-824 nm GaAlAs diode laser. The technique of wavelength modulation with third-harmonic line locking and second-harmonic detection was used to derive the line parameters with accuracies of several percent from measurements with absorptivities as low as 0.002. The linewidths and temperature coefficients are in good agreement with theoretical calculations and with recent measurements in the (2 2 1) and (3 0 1) bands. Absolute line strengths have been derived from measurements on two of the lines and are found to be 21 +/- 4 percent higher than the values listed in the 1991 HITRAN compilation.