Multiphoton dissociation and thermal unimolecular reactions induced by infrared lasers. [REAMPA code]

Technical Report · Wed Apr 01 00:00:00 EST 1981

DOI:https://doi.org/10.2172/6353059· OSTI ID:6353059

Dai, H L

Multiphoton dissociation (MPD) of ethyl chloride was studied using a tunable 3.3 ..mu..m laser to excite CH stretches. The absorbed energy increases almost linearly with fluence, while for 10 ..mu..m excitation there is substantial saturation. Much higher dissociation yields were observed for 3.3 ..mu..m excitation than for 10 ..mu..m excitation, reflecting bottlenecking in the discrete region of 10 ..mu..m excitation. The resonant nature of the excitation allows the rate equations description for transitions in the quasicontinuum and continuum to be extended to the discrete levels. Absorption cross sections are estimated from ordinary ir spectra. A set of cross sections which is constant or slowly decreasing with increasing vibrational excitation gives good fits to both absorption and dissociation yield data. The rate equations model was also used to quantitatively calculate the pressure dependence of the MPD yield of SF/sub 6/ caused by vibrational self-quenching. Between 1000-3000 cm/sup -1/ of energy is removed from SF/sub 6/ excited to approx. > 60 kcal/mole by collision with a cold SF/sub 6/ molecule at gas kinetic rate. Calculation showed the fluence dependence of dissociation varies strongly with the gas pressure. Infrared multiphoton excitation was applied to study thermal unimolecular reactions. With SiF/sub 4/ as absorbing gas for the CO/sub 2/ laser pulse, transient high temperature pulses were generated in a gas mixture. IR fluorescence from the medium reflected the decay of the temperature. The activation energy and the preexponential factor of the reactant dissociation were obtained from a phenomenological model calculation. Results are presented in detail. (WHK)

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6353059
• Report Number(s): LBL-12626; TRN: 81-010843
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
CHLORINATED ALIPHATIC HYDROCARBONS
DISSOCIATION
PHOTON-MOLECULE COLLISIONS
COMPUTER CODES
R CODES
SILICON FLUORIDES
SULFUR FLUORIDES
ABSORPTION SPECTRA
ACTIVATION ENERGY
ARRHENIUS EQUATION
COMPUTER CALCULATIONS
CROSS SECTIONS
ENERGY LEVELS
EXCITATION
EXPERIMENTAL DATA
FLUORESCENCE
GRAPHS
INFRARED RADIATION
LASERS
MATHEMATICAL MODELS
PRESSURE DEPENDENCE
PYROLYSIS
THEORETICAL DATA
VIBRATIONAL STATES
CHEMICAL REACTIONS
COLLISIONS
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENERGY
ENERGY-LEVEL TRANSITIONS
EQUATIONS
EXCITED STATES
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENATED ALIPHATIC HYDROCARBONS
INFORMATION
LUMINESCENCE
MOLECULE COLLISIONS
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PHOTON COLLISIONS
RADIATIONS
SILICON COMPOUNDS
SPECTRA
SULFUR COMPOUNDS
THERMOCHEMICAL PROCESSES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena