The 14 μm bands of BF3-CO complexes: Isotopedependent chaotic fine structure J. Chem. Phys. 98, 3612 (1993); 10.1063/1.464038 Freejet infrared absorption spectroscopy of rare gas-1 1BF3 complexes in the 7 μm region High resolution infrared absorption spectra of rare gas (Rg)-BF3 van del' Waals complexes are studied in the 14 f.1m region near the 1'2 band of BF3 monomer. Spectroscopic constants are determined for the 2oNe_llBF 3' Ar_JO,IlBFJ' 82-84.86Kr_IIBF3' and 84Kr-1oBF3 complexes. The observed redshifts from the monomer band origin correlate linearly with the rare gas polarizabilities. These shifts are about three times as large as those measured previously near the monomer v.) band. This mode dependence of the shifts cannot be reproduced in a consistent manner with the instantaneous vibrational dipole-induced dipole interaction model, and indicates much greater enhancement of bonding energy by the excitation of "'2 vibration. The band shifts are discussed on the basis of electrostatic interaction behveen rare gas atom and point charges on BF 3 . The anomalous band shifts for the V2 band are successfully accounted for by the interaction of vibrational dipole moment with the static induced dipole moment on the rare gas atom, which is parallel to the direction of vibrational motion. The isotope shifts observed for the Kr-BF 3 complexes and the band shifts due to the modification of force field by vdW bonding are discussed with a linear triatomic molecular model.
Infrared absorption spectra of jet-cooled four isotopic 10,11BF3–12,13CO complexes are studied in the 14 μm region. The spectra of the 10BF3–12CO and 10BF3–13CO complexes are parallel bands with unresolved K-structure characteristic of a heavy symmetric top molecule. On the other hand, the spectra of the 11BF3–12CO and 11BF3–13CO complexes exhibit a complicated fine structure that cannot be interpreted by an ordinary semirigid molecular model. All of the observed bands are shifted to the red by 28–30 cm−1 from the ν3 band origin of uncomplexed BF3, indicating a considerable increase in bond energies by the vibrational excitation. Possible origins of the anomalous fine structure are discussed.
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