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Title: High-resolution rovibrational study of the Coriolis-coupled v12 and v15 modes of [1.1.1]propellane

Infrared spectra of the small strained cage molecule [1.1.1]propellane have been obtained at high resolution (0.0015 cm-1) and the J and K, l rovibrational structure has been resolved for the first time. We recently used combination-differences to obtain ground state parameters for propellane; over 4,100 differences from five fundamental and four combination bands were used in this process. The combination-difference approach eliminated errors due to localized perturbations in the upper state levels of the transitions and gave well-determined ground state parameters. In the current work, these ground state parameters were used in a determination of the upper state parameters for the v12(e') perpendicular and v15(a2") parallel bands. Over 4000 infrared transitions were fitted for each band, with J, K values ranging up to 71, 51 and 92, 90 respectively. While the transition frequencies for both bands can be fit nicely using separate analyses for each band, the strong intensity perturbations observed in the weaker v12 band indicated that Coriolis coupling between the two modes was significant and should be included. Due to correlations with other parameters, the Coriolis coupling parameter ζy15,12a for the v15 and v12 interaction is poorly determined by a transition frequency fit alone. However, by combining themore » frequency fit with a fit of experimental intensities, a value of -0.42 was obtained, quite close to that predicted from the ab initio calculation (-0.44). This intensity fit also yielded a (∂μz/∂Q15)/(∂μx/∂Q12a) dipole derivative ratio of 36.5, in reasonable agreement with a value of 29.2 predicted by Gaussian ab initio density functional calculations using a cc-pVTZ basis. This ratio is unusually high due to large charge movement as the novel central Caxial-Caxial bond is displaced along the symmetry axis of the molecule for the v15 mode.« less
Authors:
; ; ; ; ; ;
Publication Date:
OSTI Identifier:
949071
Report Number(s):
PNNL-SA-61274
20907; KP1504020; TRN: US200907%%303
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Molecular Spectroscopy, 253(1):41-50; Journal Volume: 253; Journal Issue: 1
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ORGANIC COMPOUNDS; GROUND STATES; INFRARED SPECTRA; ROTATIONAL STATES; VIBRATIONAL STATES; CORIOLIS FORCE; DENSITY FUNCTIONAL METHOD Corrected title. yh 3/9/09; Environmental Molecular Sciences Laboratory