High-resolution infrared flash kinetic spectroscopy of OH radicals

Journal Article · Thu Apr 04 04:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100160a004· OSTI ID:5636235

Schiffman, A; Nelson, Jr, D D; Robinson, M S; Nesbitt, D J ^[1]

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1. Univ. of Colorado, Boulder (United States) National Inst. of Standards and Tech., Boulder, CO (United States)

A high-resolution infrared flash kinetic spectrometer is used for time- and frequency-resolved studies of the OH radical. OH is produced by 193-nm excimer laser photolysis of HNO{sub 3}/buffer gas mixtures in a 100-cm flow tube and is probed via weak fractional absorption of light from a widely tunable (2.35-3.59 {mu}m) single-mode ({Delta}{nu} {le} 2 MHz) color center laser. The IR absorption technique allows fast ({le}10{sup {minus}6} s), sensitive (<10{sup 9} radicals/cm{sup 3} per quantum state) detection of OH and is designed to permit determination of absolute OH number densities. The spectrometer is used to measure rate constants for the reactions of OH with ethane (k{sub 1}), propane (k{sub 2}), n-butane (k{sub 3}), and isobutane (k{sub 4}). The reliability of these measurements is tested on a variety of rotational, spin-orbit, and {lambda}-doublet states, with several buffer gases, and over more than an order of magnitude of alkane concentrations. The resulting rate constants are, in units of 10{sup {minus}12} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}, k{sub 1} = 0.243 {plus minus} 0.012, k{sub 2} = 1.02 {plus minus} 0.05, k{sub 3} = 2.35 {plus minus} 0.08, and k{sub 4} = 2.11 {plus minus} 0.09. The rate constants for the ethane, n-butane, and isobutane reactions agree with some previous determinations but are found to be between 10% and 25% lower than values currently used in atmospheric modeling; it is recommended that these values be revised to reflect the lower rates from this study. Current models of atmospheric air flow based on these rate constants, as well as those previously accepted values, are found to be inconsistent with daily changes in observed atmospheric alkane concentrations.

• OSTI ID: 5636235
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:7; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical &amp; Spectral Procedures
400500* -- Photochemistry
54 ENVIRONMENTAL SCIENCES
540120 -- Environment
Atmospheric-- Chemicals Monitoring &amp; Transport-- (1990-)
ABSORPTION SPECTROSCOPY
AIR FLOW
ALKANES
BUTANE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COLOR CENTERS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY RESOLUTION
ETHANE
EXPERIMENTAL DATA
FLUID FLOW
GAS FLOW
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXYL RADICALS
INFORMATION
INFRARED RADIATION
INFRARED SPECTRA
INORGANIC ACIDS
KINETICS
LASER RADIATION
MATHEMATICAL MODELS
NITRIC ACID
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
POINT DEFECTS
QUANTITY RATIO
RADIATIONS
RADICALS
REACTION KINETICS
RESOLUTION
SPECTRA
SPECTROSCOPY
TIME RESOLUTION
TIMING PROPERTIES
ULTRAVIOLET RADIATION
VACANCIES