The infrared spectrum of the He-C2D2 complex.
Spectra of the helium-acetylene complex are elusive because this weakly bound system lies close to the free rotor limit. Previously, limited assignments of He-C2D2 transitions in the R(0) region of the ν3 fundamental band (≈2440 cm(-1)) were published. Here, new He-C2D2 infrared spectra of this band are obtained using a tunable optical parametric oscillator laser source to probe a pulsed supersonic slit jet expansion from a cooled nozzle, and the analysis is extended to the weaker and more difficult P(1) and R(1) regions. A term value approach is used to obtain a consistent set of "experimental" energy levels. These are compared directly with calculations using two recently reported ab initio intermolecular potential energy surfaces, which exhibit small but significant differences. Rovibrational energies for the He-C2H2 complex are also calculated using both surfaces. A Coriolis model, useful for predicting spectral intensities, is used to interpret the energy level patterns, and a comparison with the isoelectronic complex He-CO is made.
Department of Physics and Astronomy, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada.
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Moazzen-Ahmadi
National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada.
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McKellar
Department of Physical Chemistry, and Center for Research in Biological Chemistry and Molecular Materials (CIQUS), University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
Berta
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Fernández
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
David
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Farrelly