Estimation of Three‐Body Recombination Rate Constants

The temperature rise which accompanies every flash photolytic reaction interferes with, and often makes impractical, measurements of the reaction rate constants. This difficulty may be partly overcome if the whole reaction vessel is uniformly irradiated by both the photolytic and the analyzing flash lamps.A flash photolysis apparatus with these characteristics was used to study bromine atom recombination. A 10 to 15 fold gain in atomic concentration, which corresponds to a 100 to 225 fold increase in three-body recombination rate, compared with the work of previous authors, was achieved with this apparatus. The reaction rate constants were determined from the changes in absorption of Br2 at either 4 035 Å or at 4 980 Å. The recombination rate constant of bromine in an excess of helium at 90 ± 20 °C was found to be equal to (0.8 ± 0.3)109 l2 mole−2 s−1 (measured at 4 980 Å) and (0.5 ± 0.1)109 l2 mole−2 s−1 (measured at 4 035 Å). The results suggest that the technique herein described can yield meaningful data, even though the reaction was accompanied by a 105 °C temperature rise. There was little heat exchanged between the reacting gas and the walls of the reaction vessel. Consequently the reaction vessel behaved as an effective calorimeter throughout the reaction.

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Homogeneous rate of recombination of hydrogen atoms

Canadian Journal of Chemistry ◽

10.1139/v68-164 ◽

1968 ◽

Vol 46 (6) ◽

pp. 1005-1015 ◽

Cited By ~ 21

Author(s):

F. S. Larkin

Keyword(s):

Rate Constants ◽

Hydrogen Atoms ◽

First Order ◽

A Value ◽

Rate Of Decay ◽

Low Levels ◽

Three Body ◽

Conventional Type ◽

Order Surface ◽

Body Recombination

The rate of decay of hydrogen atoms has been measured in a conventional type of discharge-flow system at temperatures between 190–350 °K. The recombination fitted the equation[Formula: see text]where ks is the first order surface rate constant. No three-body recombination for M = H was observed at the low levels of dissociation (2–5%) employed. When the flow gases contained traces of water vapor and (or) oxygen as impurities, the homogeneous rate constants (k2,M) had a small positive activation energy which was due to the influence of a surface reaction between hydrogen atoms and the impurities. In the absence of impurities, true homogeneous rate constants were obtained. A value of k2,Ar = 4.6 ± 0.5 × 1015 cm6 mole−20s−1 was found at 291 °K. The temperature variation was approximately T−1/2 over the range 190–350 °K.

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Two- and Three-body Ion-Electron Recombination Rate Coefficients in Neon

Australian Journal of Physics ◽

10.1071/ph950503 ◽

1995 ◽

Vol 48 (3) ◽

pp. 503 ◽

Cited By ~ 5

Author(s):

RN Bhave ◽

R Cooper

Keyword(s):

Recombination Rate ◽

Rate Coefficient ◽

Rate Coefficients ◽

Electron Recombination ◽

Wide Range ◽

Recombination Processes ◽

Three Body ◽

Modified Theory ◽

Body Recombination ◽

Monatomic Gas

The rates of recombination of electrons with Net ions over a wide range of pressure (1001000 Torr) and at temperatures of 133, 233 and 295 K were measured. Two- and three-body recombination processes were resolved. The observed two-body rate coefficient is lower than earlier reports. The three-body rate measured agrees well with predictions from Flarinery's modified theory by Bates for termolecular ion-electron recombination in a monatomic gas.

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The association of oxygen atoms and their combination with nitrogen atoms

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1967.0015 ◽

1967 ◽

Vol 296 (1445) ◽

pp. 222-232 ◽

Cited By ~ 82

Keyword(s):

Activation Energy ◽

Temperature Coefficient ◽

Rate Constants ◽

Room Temperature ◽

Kinetic Studies ◽

Active Nitrogen ◽

Similar Temperature ◽

Three Body ◽

Body Recombination ◽

Oxygen Atoms

The rate constants of the reactions N + O + M = NO + M (2) O + O + M = O 2 + M (4) have been determined in active nitrogen systems, nitric oxide being added to result in the partial production of oxygen atoms. The concentrations of these atoms were monitored by measurements of the intensity of the N 2 First Positive emission and NO β emission. The following rate constants (in cm 6 mole –2 s –1 ) were obtained at room temperature (298 °K) N 2 Ar He 10 –15 k 2 3.88 ± 0.30 2.98 ± 0.35 1.36 ± 0.17 10 -14 k 4 11.3 ± 1.1 6.0 ± 0.6 4.6 + 0.4 In the range 196 to 327 °K, the temperature coefficient of reaction (2) corresponds to a T -½ dependence or an activation energy of –270 ± 120 cal/mole. This is unusually small for a three body recombination and contrasts with more ‘normal’ activation energy of –1420 ±350 cal/mole found for reaction (4). The NO β emission associated with reaction (2) has a similar temperature coefficient to the overall reaction, but is slightly enhanced by replacing the nitrogen carrier by argon. Our kinetic studies of this emission generally confirm the mechanism of Young & Sharpless (1962).

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