Accession Number : ADA251286


Title :   High Resolution Spectroscopy of 1,2-Difluoroethane in a Molecular Beam: A Case Study of Vibrational Mode-Coupling


Descriptive Note : Technical rept. no. 4


Corporate Author : CORNELL UNIV ITHACA NY DEPT OF CHEMISTRY


Personal Author(s) : Mork, Steven M. ; Miller, C. C. ; Philips, Laura A.


Full Text : http://www.dtic.mil/get-tr-doc/pdf?AD=ADA251286


Report Date : 29 MAY 1992


Pagination or Media Count : 49


Abstract : The high resolution infrared spectrum of 1,2-difluoroethane (DFE) in a molecular beam has been obtained over the 2978-2996 cm-1 spectral region. This region corresponds to the symmetric combination of asymmetric C-H stretches in DFE. Observed rotational fine structure indicates that this C-H stretch is undergoing vibrational mode coupling to a single dark mode. The dark mode is split by approximately 19 cm-1 due to tunneling between the two identical gauche conformers. The mechanism of the coupling is largely anharmonic with a minor component of B/C plane Coriolis coupling. Effects of centrifugal distortion along the molecular A-axis are also observed. Analysis of the fine structure identifies the dark state as being composed of C-C torsion, CCF bend and CH2 rock. Coupling between the C-H stretches and the C-C torsion is of particular interest because DFE has been observed to undergo vibrationally induced isomerization from the gauche to trans conformer upon excitation of the C-H stretch.


Descriptors :   *HIGH RESOLUTION , *MOLECULAR BEAMS , *MOLECULAR VIBRATION , *SPECTROSCOPY , STRUCTURES , COUPLINGS , TORSION , TUNNELING , EXCITATION , ISOMERIZATION , DISTORTION , INFRARED SPECTROSCOPY


Subject Categories : PHYSICAL CHEMISTRY
      ATOMIC AND MOLECULAR PHYSICS AND SPECTROSCOPY


Distribution Statement : APPROVED FOR PUBLIC RELEASE