Measurements of H₂O-O₂ line shape parameters and the determination of the intermolecular potential for modified complex Robert-Bonamy calculations

Abstract

A series of spectra, one pure H₂O and four H₂O-O₂ mixtures, were measured for the ν₂ band in the 1200–1950 cm⁻¹ region at room temperature using a single-pass copper cell housed in the Bruker 125HR high-resolution Fourier transform spectrometer (FTS) at Jet Propulsion Laboratory (JPL). All the five spectra were fit simultaneously using a multispectrum non-linear least-squares fitting software, Labfit programme suite, which adopts a speed-dependent Voigt line shape profile using full line mixing taken into account through a relaxation matrix operation. O₂-broadened half-width and O₂-induced frequency shift coefficients were determined for more than 350 transitions of H₂¹⁶O. These data were then checked using the smooth variation and paring rules [Brown et al. J Mol Spectrosc. 2007;246:1-21, Ma et al. Mol Phys. 2011;109:1925-41] and 186 transitions that obey the rules with less than 3% difference were chosen. Using these selected data, Modified Complex Robert-Bonamy calculations were made to determine the intermolecular potential for the H₂O-O₂ collision system. Some 93 potential were investigated resulting in a final potential (potential 74) that agrees with the selected half-width measurements having an average percent difference of 0.052 and a standard deviation of 5.108% between measurement and calculations.

GRAPHICAL ABSTRACT

KEYWORDS:

• High resolution infrared spectroscopy
• line shape parameters for H₂O-O₂
• modified complex
• Robert-Bonamy calculations
• earth’s atmospheres

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The research at the Jet Propulsion Laboratory (JPL), California Institute of Technology, was performed under contracts with the National Aeronautics and Space Administration. R.R. Gamache, K. Sung, and G. Toon are pleased to acknowledge support from NASA ROSES-NRA: NNH20ZDA001N-XRP [grant number 20-XRP20_2-0063]. B. Vispoel would like to thank the F.R.S.-FNRS for postdoctoral financial support.