Analysis of Newly Derived Pressure Self-Induced Line Shape Parameters for the H2O v2 Band

Kurzfassung

High-resolution transmission spectra of pure water vapor in the spectral region of the v2 band (700-2000 cm-1) were recorded using a Bruker IFS 125 HR Fourier-transform spectrometer in combination with a multi-reflection cell. Spectra were measured at absorption path lengths between 14 and 161 m, water vapor pressures ranging from 0.003 to 20 mbar, and temperatures between 278 and 350 K.

The spectra were corrected for detector nonlinearity, thermal self-emission, and deviations from the ideal instrumental line shape. A micro-window-based multispectrum fitting approach was applied using a quadratic speed-dependent Voigt profile extended to include Rosenkranz line mixing. This analysis yielded new line parameters for more than 4000 transitions of the four most abundant water isotopologues, which were compiled into a dedicated database [1].

The present work focuses on the newly derived pressure self-induced parameters, including the self-broadening coefficients gamma0,self and gamma2,self, the temperature exponent nself, as well as the self-shift parameters delta0,self and their temperature dependence parameters deltaT,self, all of which are included in HITRAN2024 [2]. Where available, the retrieved parameters are compared with both experimental and theoretical results reported by other groups.

The analysis demonstrates a significantly improved consistency of the derived parameters, revealing smooth trends of gamma0,self as a function of |m| quantum number that were not evident in previous datasets. In addition, correlations between different line-shape parameters are investigated, and systematic comparisons are presented for transitions sharing the same quantum-number across the different isotopologues.

References:

[1] Röske, C., et al. "Line parameter database H2O self-broadened 700-2000 cm-1 [Data set].". Zenodo (2024). [2] Gordon, I. E., et al. "The HITRAN2024 molecular spectroscopic database." Journal of Quantitative Spectroscopy and Radiative Transfer (2026): 109807.