Experimental Oscillator Strength of OH, 2Σ+→2Π, by a Chemical Method

Golden, David M.; Greco, Frank P. Del; Kaufman, F.

doi:10.1063/1.1734139

Cited by 70 publications

(5 citation statements)

References 16 publications

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“…Values obtained from the absorption data were from 80-97% of the calculated equilibrium concentration of hydroxyl radicals in the burnt gas. This is within the accuracy of the method which is ± 50 % under favourable circumstances, the major source of uncertainty being the band oscillator strength (Golden et al (1963». Although the absorption method using the continuous source was suitable for concentrations of hydroxyl less than I x 10-3 mass fraction, for higher concentrations the method is unsatisfactory unless a spectrometer of very high resolving power is used. For a medium resolution spectrometer of the kind used in this work, the linear dependence of hydroxyl concentration on absorption falls off rapidly as the absorption increases much above 10% (Oldenberg and Rieke (1938), Smith (1969».…”

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confidence: 75%

The Structure of a Reaction-Broadened Diffusion Flame

Melvin¹,

Moss²,

Clarke

1971

Combustion Science and Technology

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Results of an experimental investigation of the structure of flat diffusion flames on a Parker-Wolfhard burner are compared with theoretical predictions of perturbation solutions which incorporate realistic schemes for the chemical kinetics. Measurements of hydroxyl radical concentrations show that the flames are reaction-broadened for temperatures below 1950OK, while at higher temperatures reaction zone structure is of equilibriumbroadened type. Experiment also shows that, close to extinction, there is significant convective transfer of material from one stream to the other at the flame base. It is suggested that the consequent disruption of mixing in, or shielding of, the reaction zone makes extinction a progressive process. Complementary studies of spherical and counter flow diffusion flames suggest that the former geometry is preferable in future studies designed to test hypotheses about the role of kinetics in diffusion flame extinction.Despite the practical importance of laminar diffusion flames, they have received relatively little attention in comparison with premixed flames, which have been studied extensively. Part of this neglect has been due to the lack of an adeq uate treatment of diffusion flame structure. In the main, this lack can be ascribed to the two-dimensional nature of most steady diffusion flames. Since premixed flames can often be made quasi-unidimensional, solution of the appropriate conservation equations is a relatively much more simple problem. As a result, many of the studies of diffusion flames which appear in the literature are concerned not with structure but with ancillary problems e.g. carbon formation. Burke and Schumann (1928) produced the first simple treatment of diffusion flame structure for a single reaction of infinite rate. This model was modified in an empirical way by Barr (1949) but Fendell (1965) Chung and Blankenship (1966 and Clarke (1967a, b) interpreted the original BurkeSchumann flame sheet model as a singular perturbation problem. The model was extended by the method of matched asymptotic expansions for sets of reactions in chemical equilibrium by Clarke (1968) and for systems not in that chemical state also by Clarke (1969). The burner configuration dealt with was an idealisation of the two-dimensional Parker-Wolfhard burner and the conservation equations were simplified by use of the Oseen approximation. Clarke and Moss (1970) have recently applied a similar analysis to the 3 one-dimensional spherical diffusion flame (for which the Oseen approximation is now unnecessary) and have tentatively interpreted a breakdown in the analysis for reaction-broadened hydrogen-oxygen flames as a possible kinetically-controlled extinction condition operating in the region of 1500 OK. The work on hydrogen-oxygen flames also leads to prediction of hydroxyl radical concentrations in the reaction zones of these flames. There appears to be no relevant experimental information on extinction conditions or on hydroxyl radical concentrations for such diffusion flames in which the rea...

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confidence: 75%

The Structure of a Reaction-Broadened Diffusion Flame

Melvin¹,

Moss²,

Clarke

1971

Combustion Science and Technology

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“…The 2 2 1/2 + state lifetime has been measured in a number of experiments as reviewed by Golden, Del Greco, and Kaufman. 10 Although earlier work shows a large spread of values, the recent results of Bennet and Dalby 11 and of Golden, Del Greco, and Kauf- man, 10 obtained by careful application of two different methods, are in excellent agreement with one another. The oscillator strengths/(Q t 4) and /(P x 2) measured by Golden, Del Greco, and Kaufman, when combined with the relative line strengths for competing transitions tabulated by Dieke and Crosswhite, 4 yield independently r = 1.03 xlO -6 sec and r = 1.05xl0~6 sec for the K = 4, J= f and K = 1, J = f rotational sublevels of the 2 S 1/2 + state.…”

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confidence: 76%

Level-Crossing Spectroscopy in Molecules: Application to the OH Free Radical

1969

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We have observed the Hanle effect in the 2 2 (v = 0) excited state of the free radical OH in lines which originate from sublevels with rotational quantum numbers K=3,4, 5. From the widths of each of these experimental signals we can calculate the ^--factor-lifetime product and, since the lifetime of the state has been measured previously, our observations yield the values g[K = 3] =0.176 (23), g[K = 4] =0.141(15), andg[K=5] =0.118(11).

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“…mole/l. can be estimated from thef number of the Q1-4 doublet of the 0, 0 band given by Golden et al [19].…”

Section: A Apparatusmentioning

confidence: 99%

A quantitative study of alkyl radical reactions by kinetic spectroscopy. II. Combination of the methyl radical with the oxygen molecule

Basco

James

1972

Int J of Chemical Kinetics

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The kinetics of the reaction CH3 + 0 2 (+M) -+ CH302 (+MI have been studied, using the technique of flash photolysis and kinetic spectroscopy to follow the methyl radical concentration. The order of the reaction lies between 2 and 3 throughout the range of pressure from 25 to 380 torr at 22"C, and the results are consistent with a single reaction sequence:The limiting values of the third-order rate coefficients at low pressures are (3.6 f 0.3) X 10" 1. mole-2 sec-' when M is neopentane, and (0.94 f 0.03) X 10" L 2 mole-2 sec-' when M is nitrogen. The limiting value of the second-order rate coefficient at high pressures is (3.1 f 0.3) X lo8 1. mole-' sec-I. The rate constant for the independent second-order reaction CH3 + 0 2 -+ CH20 + OH is shown to be not much greater than 2 X lo5 1. mole-' sec-I, so that this reaction does not complete significantly with the combination reaction.This new interpretation is contrary to currently accepted views.

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Experimental Oscillator Strength of OH, 2Σ+→2Π, by a Chemical Method

Cited by 70 publications

References 16 publications

The Structure of a Reaction-Broadened Diffusion Flame

The Structure of a Reaction-Broadened Diffusion Flame

Level-Crossing Spectroscopy in Molecules: Application to the OH Free Radical

A quantitative study of alkyl radical reactions by kinetic spectroscopy. II. Combination of the methyl radical with the oxygen molecule

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