Additional high-resolution lines in the ν3 CO2 fundamental band of the rovibrational spectrum of He2-CO2 have been observed using a tunable infrared laser to probe a pulsed supersonic jet expansion. The ro-vibrational spectrum was calculated using Euler angles and five vibrational coordinates that specify the positions of the He atoms with respect to the CO2 molecule, a product basis, and a Lanczos eigensolver. Rotational states with J = 0, 1, 2, and 3 associated with the vibrational ground state and different states (νt) of the torsional motion of the two He atoms about the CO2 axis are identified and assigned. The assignment is consistent with having different principle axis orientiations in νt = 0 and νt = 1 states. Δνt = 1 infrared transistions are forbidden due to the symmetry of CO2, but Δνt = 1 microwave transistions are possible. Theoretical line positions and intensities are predicted. Good agreement between experiment and theory was obtained. The calculated energy levels and intensities were crucial in assigning some of the weaker observed transitions.
ASJC Scopus subject areas
- Physics and Astronomy(all)