Millimeter-wave detection of free radicals using pulsed laser photolysis

Journal Article · Thu Aug 01 04:00:00 EDT 1985 · Rev. Sci. Instrum.; (United States)

DOI:https://doi.org/10.1063/1.1138156· OSTI ID:5525662

Kolbe, W F; Leskovar, B

The application of millimeter-wave microwave spectroscopy to the detection of free radicals and other species generated by pulsed excimer laser photolysis is described. To detect the radical species, a newly developed 140-GHz microwave spectrometer employing a high-Q Fabry--Perot cavity was used. The technique is illustrated by the observation of SO and CS radicals produced by photodissociation at 193 nm of SO/sub 2/ and CS/sub 2/, respectively. SO absorption signals from the ground vibrational state transition at 138.17 GHz and the first and second excited vibrational state transitions at 137.28 and 136.45 GHz were measured. CS was detected in several excited vibrational states up to ..nu.. = 4. Finally, as an example of the application of the technique to chemical kinetic studies, the reaction rate of SO with NO/sub 2/ was determined. The measured rate coefficient at 298 K of (1.46 +- 0.12) x 10/sup -11/ cm/sup 3/ molecule/sup -1/ s/sup -1/ is in excellent agreement with values reported in other studies. Millimeter-wave spectroscopy is shown to be a sensitive and highly specific probe for the detection of short lived species in gas phase chemical kinetic studies.

• Research Organization: Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5525662
• Journal Information: Rev. Sci. Instrum.; (United States), Journal Name: Rev. Sci. Instrum.; (United States) Vol. 56:8; ISSN RSINA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400104* -- Spectral Procedures-- (-1987)
440300 -- Miscellaneous Instruments-- (-1989)
47 OTHER INSTRUMENTATION
ABSORPTION SPECTRA
CARBON COMPOUNDS
CARBON SULFIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DESIGN
DISSOCIATION
ENERGY LEVELS
EXCIMER LASERS
EXCITED STATES
EXPERIMENTAL DATA
FABRICATION
GAS LASERS
INFORMATION
KINETICS
LASERS
MEASURING INSTRUMENTS
MEASURING METHODS
MICROWAVE SPECTRA
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN OXIDES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADICALS
REACTION KINETICS
SPECTRA
SPECTROMETERS
SULFIDES
SULFUR COMPOUNDS
SULFUR OXIDES
VIBRATIONAL STATES