Diode-laser measurements of linestrength and temperature-dependent lineshape parameters for H2O transitions near 1.4 μm using Voigt, Rautian, Galatry, and speed-dependent Voigt profiles

- Temperature-dependent lineshape parameters and linestrengths were measured for 7 H2O transitions near 1.4 μm at 300 to 1300 K.
- Voigt, Rautian, Galatry, and speed-dependent Voigt profile parameters were obtained for H2O and N2 perturbers.
- Transitions with J″=10-18 exhibited N2-broadening coefficients that increased with increasing temperature.
- Collisional-narrowing and speed-dependent-broadening coefficients trended similarly with temperature and J″.

Linestrengths and lineshapes for 7 H2O absorption transitions in the ν1+ν3 combination band near 1.4 μm were measured at high resolution using tunable diode laser absorption. H2O- and N2-perturbed lineshapes were measured at 300-1300 K and 2-760 Torr and Voigt, Galatry, Rautian, and quadratic-speed-dependent-Voigt profiles were least-squares fit to measured spectra using a multi-spectrum fitting routine. Transitions with J″ of 6-18 were studied to highlight the importance of collisional resonance and illustrate how the best-fit lineshape parameters varied with J″. The accuracy of the Voigt profile decreased as J″ increased (especially for J=Kc doublets). For transitions in N2, the collisional-broadening temperature exponents varied from ≈0.8 to −0.4 (for the Voigt profile) as J″ increased and this behavior coincided with increasing speed-dependent collisional-broadening coefficients. The quadratic-speed-dependent Voigt profile was found to offer the best combination of accuracy and robust lineshape parameters; however, Rautian and Galatry profiles provided similar performance.