High-resolution, near-infrared CW-CRDS, and ab initio investigations of N2O-HDO

• Published in: Molecular physics Vol. 113; no. 5; pp. 473 - 482
• Main Authors: Földes, T., Lauzin, C., Vanfleteren, T., Herman, M., Liévin, J., Didriche, K.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 04.03.2015; Taylor & Francis Ltd
• Subjects: ab initio calculation; cavity ring-down spectroscopy; molecular complex; overtone spectroscopy; Spectrum analysis
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2014.953611

We have investigated the N 2 O-HDO molecular complex using ab initio calculations at the CCSD(T)-F12a/aug-cc-pVTZ level of theory and using cavity ring-down spectroscopy to probe an HDO/N 2 O/Ar supersonic jet around 1.58 μm. A single a-type vibrational band was observed, 13 cm −1 redshifted compared to the OH+OD excited band in HDO, and 173 vibration-rotation lines were assigned (T rot ≈ 20 K). A weighted fit of existing microwave and present near infrared (NIR) data was achieved using a standard Watson's Hamiltonian (σ = 1.26), producing ground and excited states rotational constants. The comparison of the former with those calculated ab initio suggests a planar geometry in which the OD rather than the OH bond in water is almost parallel to NNO. The equilibrium geometry and dissociation energy (D e = -11.7 kJ/mol) of the water-nitrous oxide complex were calculated. The calculations further demonstrate and allow characterising another minimum, 404 cm −1 (ΔE 0 ) higher in energy. Harmonic vibrational frequencies and dissociation energies, D 0 , were calculated for various conformers and isotopic forms of the complex, in both minima. The absence of N 2 O-D 2 O from dedicated NIR experiments is reported and discussed.