High overtone spectroscopy of polyatomic molecules

Technical Report · Tue Dec 01 00:00:00 EST 1981

OSTI ID:5225779

Wong, J S

Overtone spectra of the C-H stretching vibrations were observed using laser photoacoustic spectroscopy in the visible and Fourier transform infrared spectroscopy in the near-infrared. The microcomputer-controlled, laser photoacoustic spectrometer is described in detail. The fifth overtone spectra of gaseous alkanes and alkenes were analyzed using the local mode model, and resolvable peaks were seen for each inequivalent C-H bond. Correlations of overtone transition energies with C-H bond lengths and isolated fundamental frequencies were found. The integrated cross sections per C-H oscillator varied by a factor of two about the average value of (1.08+-0.28) x 10/sup -23/ cm/sup 2/ cm/sup -1/. Local mode spectra of cycloalkanes and cycloalkenes were observed using both gas phase high overtone and isotopically isolated fundamental spectroscopy. The shapes of the bands reflect the changes in the C-H bonds during conformational motion. Absorptions by axial and equatorial type C-H bonds were resolved in cyclobutane, cyclopentane, cyclopentene and cyclohexane and the isotopically isolated fundamentals were close to the frequencies extrapolated from the overtones except for liquid cyclohexane. The equatorial bands are consistently more intense than the axial ones. Spectra of chloroform, fluoroform, dichlorofluoromethane and chlorodifluoromethane are observed from the fundamentals through the fifth overtone of the C-H stretching vibrations. Fermi resonant combination bands with one less C-H stretching quantum plus two quanta of the C-H bending vibrations, along with the C-H stretching overtones, dominate the spectra. The intensities of these combination bands increase with the level of vibrational excitation, indicating strong, intramolecular mode coupling.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5225779
• Report Number(s): LBL-13868; ON: DE82007860
• Resource Relation: Other Information: Thesis. Portions of document are illegible
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKANES
VIBRATIONAL STATES
ALKENES
CHLORINATED ALIPHATIC HYDROCARBONS
CHLOROFORM
CYCLOALKANES
CYCLOHEXANE
ETHANE
ETHYLENE
FLUORINATED ALIPHATIC HYDROCARBONS
FLUOROFORM
METHANE
DESIGN
PHOTOACOUSTIC SPECTROMETERS
PROPANE
PROPYLENE
EXPERIMENTAL DATA
FOURIER TRANSFORMATION
INFRARED SPECTRA
LASERS
PHOTOACOUSTIC SPECTROSCOPY
VISIBLE SPECTRA
DATA
ENERGY LEVELS
EXCITED STATES
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROCARBONS
INFORMATION
INFRARED SPECTROMETERS
INTEGRAL TRANSFORMATIONS
MEASURING INSTRUMENTS
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
SPECTRA
SPECTROMETERS
SPECTROSCOPY
TRANSFORMATIONS
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)