| Résumé | Infrared spectra of weakly bound CO₂-H₂ complexes have been studied in the region of the CO₂ v₃ asymmetric stretch, using a tunable diode laser probe and a pulsed supersonic jet expansion. For CO₂-paraH₂, results were obtained for three isotopic species, ¹²C¹⁶O₂, ¹³C¹⁶O₂, and ¹²C¹⁸O₂. These spectra were analyzed using an asymmetric rotor Hamiltonian, with results that resembled those obtained previously for OCS- and N₂O-paraH₂, except that half the rotational levels were missing due to the symmetry of CO₂ and the spin statistics of the ¹⁶O or ¹⁸O nuclei. However, for CO₂-orthoH₂, more complicated spectra were observed which could not be assigned, in contrast with OCS- and N₂O-H₂ where the paraH₂ and orthoH₂ spectra were similar, though distinct. The CO₂-paraH₂ complex has a T-shaped structure with and intermolecular distance of about 3.5 Å, and the CO₂ v₃ vibration exhibits a small redshift (-0.20 cm⁻¹) in the complex. |
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