Highhyphen;resolution infrared absorption spectra of the van der Waals complexes of BF3with a rare gas atom (Ne, Ar, and Kr) are obtained near the ngr;3band of BF3monomer in a supersonic free jet. Each spectrum shows a characteristic perpendicular band of a symmetrichyphen;top molecule withC3vsymmetry. The bands are shifted toward the red with respect to the monomer band by 0.3933(4), 1.7609(1), and 2.4059(4) cmminus;1for NeBF3, ArBF3, and KrBF3, respectively. The Coriolis coupling constants of the complexes are almost identical to that of the monomer. These results show that complexing with a rare gas atom does not strongly influence the ngr;3vibrational motion in BF3. The observed red shifts correlate well with the polarizabilities of the rare gas atoms. This finding is explained in terms of the instantaneous dipolendash;induced dipole interaction. The observed full widths of the Dopplerhyphen;limited spectral lines, typically 70 MHz, indicate that the lower limit of the vibrational predissociation lifetime is 2 ns.
展开▼
