Direct study of the reactions of CH/sub 2/(X(tilde) /sup 3/B/sub 1/) radicals with H and D atoms
The following reactions of CH/sub 2/ radicals in their triplet electronic ground state X(tilde) /sup 3/B/sub 1/ with hydrogen and deuterium atoms were investigated at room temperature and pressures of a few mbar in an isothermal discharge flow reactor: CH/sub 2/(X(tilde) /sup 3/B/sub 1/) + H(/sup 2/S) ..-->.. CH(/sup 2/II) + H/sup 2/(/sup 1/..sigma..) (1a) ..-->.. CH/sub 3/(/sup 2/A/sub 2/'') (1b); CH/sub 2/(X(tilde) /sup 3/B/sub 1/) + D(/sup 2/S) ..-->.. CH(/sup 2/II) + HD(/sup 1/..sigma..) (2a), ..-->.. CD(/sup 2/II) + H/sub 2/(/sup 1/..sigma..) (2b), ..-->.. CHD(/sup 3/B/sub 1/) + H(/sup 2/S) (2c), ..-->.. CH/sub 2/D(/sup 2/A/sub 2/'') (2d). CH/sub 2/ and CH radicals were detected with a far-infrared laser magnetic resonance (LMR) spectrometer while H and D atoms were monitored via their Lyman-..cap alpha.. vacuum ultraviolet resonance absorption. Direct measurements of the pseudo-first-order decay of (CH/sub 2/) in the presence of an excess of H or D yielded the rate constants k/sub 1/(298 K) = (1.1 +/- 0.3) x 10/sup 14/ cm/sup 3//(mol s) and k/sub 2/(298 K) = (1.1 +/- 0.3) x 10/sup 14/ cm/sup 3//(mol s). Under the conditions used the recombination channels 1b and 2d are negligible. Thus, the measured values correspond to k/sub 1/ = k/sub 1a/ and k/sub 2/ = K/sub 2a/ = k/sub 2b/ = k/sub 2c/. When the value for k/sub 1a/ is combined with literature data for the reverse reaction CH + H/sub 2/ ..-->.. CH/sub 2/ + H (-1a), the heat of formation of CH/sub 2/ radicals was found to be ..delta..H/sub f//sup 0/ /sub 298/(CH/sub 2/(X(tilde)/sup 3/B/sub 1/)) = 389 +/- 4 kJ/mol.
- Research Organization:
- Max-Planck-Institut fuer Stroemungsforschung, Goettingen, West Germany
- OSTI ID:
- 6358291
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 91:5
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DEUTERIUM
CHEMICAL REACTIONS
HYDROGEN
METHYLENE RADICALS
FORMATION HEAT
GROUND STATES
CHEMICAL REACTION KINETICS
EXPERIMENTAL DATA
LASERS
MAGNETIC RESONANCE
MEDIUM PRESSURE
MEDIUM TEMPERATURE
RESONANCE ABSORPTION
TRIPLETS
ABSORPTION
DATA
ELEMENTS
ENERGY LEVELS
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ODD-ODD NUCLEI
PHYSICAL PROPERTIES
RADICALS
REACTION HEAT
REACTION KINETICS
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STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
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