Nonequilibrium photochemical reactions induced by lasers. Final report
The work carried out under this contract has addressed two principal issues: how the multiple infrared photon excitation process is initiated in a polyatomic molecule; and how to understand the chemical processes which ensue following such excitation. The first question has been addressed by the technique of diode-infrared laser-double resonance. Sulfur hexafluoride was chosen as the test molecule. Power broadening induced by the pump beam, transitions in the 2 ..nu../sub 3/ reverse arrow ..nu../sub 3/ manifold, and relaxations within the ..nu../sub 3/ vibrational level brought about by collisions between SF/sub 6/ and other molecules of SF/sub 6/, He, and CH/sub 3/F have been observed. The results indicate that rotational broadening of the excited-state absorption band envelopes may play a significant role in anharmonicity compensation, and that rotational relaxation proceeds mainly by collisions which reorient the angular momentum with respect to the internal coordinates of the SF/sub 6/ molecules, but leave the total J quantum number nearly unchanged. The double resonance signals have now been satisfactorily interpreted in terms of standard 2- and 3- level models, with the possible exception of some collisional redistribution of intensity. From the excited-state-absorption signals, some of the spectroscopic parameters of the (n > 1)..nu../sub 3/ levels can be determined. The infrared photochemistry of a series of chloro-substituted ethylenes has been studied. The primary reaction mode has been established as 3-center elimination of HCl, leading in some cases to a transient vinylidenecarbene (R/sub 2/C=C:) intermediate. The kinetics can be fully accounted for in terms of RRKM unimolecular rate theory.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Chemistry
- DOE Contract Number:
- AS02-76ET33056
- OSTI ID:
- 6789787
- Report Number(s):
- DOE/ET/33056-15
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHLORINATED ALIPHATIC HYDROCARBONS
CHEMICAL REACTION KINETICS
PHOTOCHEMICAL REACTIONS
LASER ISOTOPE SEPARATION
RESEARCH PROGRAMS
SULFUR FLUORIDES
EXCITED STATES
HELIUM
HYDROCHLORIC ACID
INFRARED RADIATION
LASER RADIATION
LASERS
METHYL FLUORIDE
MOLECULE COLLISIONS
PHOTON BEAMS
REACTION INTERMEDIATES
RESONANCE
VIBRATIONAL STATES
BEAMS
CHEMICAL REACTIONS
COLLISIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY LEVELS
FLUIDS
FLUORIDES
FLUORINATED ALIPHATIC HYDROCARBONS
FLUORINE COMPOUNDS
GASES
HALIDES
HALOGEN COMPOUNDS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
ISOTOPE SEPARATION
KINETICS
NONMETALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADIATIONS
RARE GASES
REACTION KINETICS
SEPARATION PROCESSES
SULFUR COMPOUNDS
400500* - Photochemistry
400203 - Isotope Exchange & Isotope Separation- (-1987)