부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jms.2006.03.003 Byline: Robynne Kirkpatrick (a), Tony Masiello (b), Alfons Weber (c), Joseph W. Nibler (a) Keywords: Coherent Raman spectroscopy; CARS spectroscopy; Rovibrational spectrum; High resolution; Ab initio; Boron trifluoride; Boron-10; Boron-11 Abstract: High resolution (0.001cm.sup.-1) coherent anti-Stokes Raman spectroscopy (CARS) was used to directly examine the [nu].sub.1 symmetric stretching mode of the planar symmetric D.sub.3h molecules.sup.10BF.sub.3 and.sup.11BF.sub.3. Simulations of the spectra were done using [nu].sub.1 rovibrational parameters deduced from published infrared hot-band and difference-band studies and the close similarity to the observed CARS spectra confirms the validity of the infrared constants. No significant perturbations by Fermi resonance or Coriolis interactions with nearby states are observed, in marked contrast to the case of sulfur trioxide, a similar D.sub.3h molecule recently studied. In the harmonic approximation, the.sup.10BF.sub.3 and.sup.11BF.sub.3 [nu].sub.1 Q-branches would be identical since the isotopic substitution is at the center of mass but, interestingly, the [nu].sub.1 stretching frequency for.sup.11BF.sub.3 is found to be 0.198cm.sup.-1 higher than for the lighter.sup.10BF.sub.3 isotopomer. This counterintuitive result is reproduced almost exactly (0.200cm.sup.-1) by ab initio calculations (B3LYP/cc-pVTZ) that included evaluation of cubic and quartic force constants and x.sub.ij anharmonicity constants. The ab initio computations also predict to within 1% the [DELTA]B, [DELTA]C changes in the rotational constants in going from the ground state to the v.sub.1 =1 vibrational level. The results illustrate nicely the complementary interplay of modern infrared, Raman, and ab initio methods in obtaining and analyzing rovibrational spectra. Author Affiliation: (a) Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003, USA (b) Pacific Northwest National Laboratory, P.O. Box 999, Mail Stop K8-88, Richland, WA 99352, USA (c) National Institute of Standards and Technology, Gaithersburg, MD 20899, USA Article History: Received 25 January 2006; Revised 2 March 2006