Tunable Diode Laser Measurements of Water Vapor Line Parameters in the 6-μm Spectral Region

Abstract

High-resolution infrared diode laser spectroscopy has been used to determine line strengths, foreign-, and self-broadening coefficients for several transitions in the ν2 band of H2O near 6 μm. Sources of systematic experimental error, most notably stray radiation from off-axis modes and thermal etalon effects, were detected and characterized. Their effects on the resulting line parameters were minimized by making appropriate corrections or adjusting experimental conditions such as laser current and temperature. Measured line strengths are found to agree to better than 5% with one published tabulation. Foreign-gas broadening coefficients compare favorably with theoretical values, whereas measured self-broadening coefficients were found to be systematically less.