High-resolution spectroscopic study of the H₂O–CO₂ van der Waals complex in the 2OH overtone range

Abstract

The jet-cooled spectrum ($T_{\mathrm{r}\mathrm{o}\mathrm{t}}=12$K) of the H${}_2$O–CO${}_2$ van der Waals complex has been recorded in the 1.4 μm region by cavity ring-down spectroscopy. Two b-type vibrational bands have been observed and analysed. The rotational assignment has been achieved using a different asymmetric rotor Hamiltonian for each nuclear spin species, accounting for the internal rotation of the H${}_2$O and CO${}_2$ units. The band at 7247 cm${}^{-1}$ is assigned to (101) in terms of the ($v_1{v}_2{v}_3$) vibrational quantum number of the H${}_2$O monomer. The band at 7238 cm${}^{-1}$ is assigned to (200) + an intermolecular mode ($v_{12}$) excited in the complex. Vibration-rotation constants are provided for the excited states. The symmetry of the wavefunction, the effect of vibrational excitation on the tunnelling dynamics and the vibrational assignment are discussed.

GRAPHICAL ABSTRACT

Keywords:

• Van der Waals complexes
• tunnelling
• cavity ring-down
• combination band

Acknowledgments

The authors thank Dr. J. Bowman for fruitful discussion concerning the irreducible representations of the intermolecular modes. The authors are indebted to the Service de ‘Chimie Quantique et Photophysique’ of the ‘Universit Libre de Bruxelles’ for the loan of the FANTASIO set-up.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

C. L. thanks the financial support of the Fonds De La Recherche Scientifique - FNRS under grant number J.0179.18 (CDR-Sensitive Optical Spectroscopy at 20 K) and the Action de Recherches Concertes (ARC Ibeam-18/23-090). Fédération Wallonie-Bruxelles