The acetyl radicals CH3CO· and CD3CO· studied by flash photolysis and kinetic spectroscopy

1981 ◽  
Vol 13 (12) ◽  
pp. 1251-1276 ◽  
Author(s):  
Hiroyuki Adachi ◽  
N. Basco ◽  
D. G. L. James
Keyword(s):  
Flash Photolysis ◽  
Kinetic Spectroscopy

Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy I. Free radical absorption spectra in acetylene combustion

1953 ◽  
Vol 216 (1125) ◽  
pp. 165-183 ◽  
Keyword(s):  
Absorption Spectra ◽  
Total Pressure ◽  
Flash Photolysis ◽  
Initial Period ◽  
Kinetic Spectroscopy ◽  
Radical Concentration ◽  
Stage 4 ◽  
Explosive Reaction ◽  
Stage 1 ◽  
Flash Spectroscopy

The explosive oxidation of acetylene, initiated homogeneously by the flash photolysis of a small quantity of nitrogen dioxide, has been investigated by flash spectroscopy. The absorption spectra of OH, CH, C 2 (singlet and triplet), C 3 , CN and NH, a number of which have not previously been observed, are described, and the relative concentrations, at all times throughout the explosion, are given. Four stages have been distinguished in the explosive reaction: 1. An initial period during which only OH appears. 2. A rapid chain branching involving all the diatomic radicals. 3. Further reaction, occurring only when oxygen is present in excess of equimolecular proportions, during which the OH concentration rises exponentially and the other radicals are totally consumed. 4. A relatively slow exponential decay of the excess radical concentration remaining after completion of stages 2 and 3. The duration of stage 1 is 0 to 3 ms. In an equimolecular mixture at 20 mm total pressure, containing 1.5 mm NO 2 , the durations of both stage 2 and stage 3 are approximately 10 -4 s and the half-life of OH in stage 4 is 0.28 ms. A preliminary interpretation of these changes and of the radical reactions is given.

The Reaction of S(3P) Atoms with Molecular Oxygen

1971 ◽  
Vol 49 (10) ◽  
pp. 1659-1664 ◽  
Author(s):  
R. W. Fair ◽  
A. Van Roodselaar ◽  
O. P. Strausz
Keyword(s):  
Molecular Oxygen ◽  
Rate Constant ◽  
Ground State ◽  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Ultraviolet Region ◽  
Kinetic Spectroscopy ◽  
Vacuum Ultraviolet Region

The rate constant of the reaction of ground state S(3P) atoms with molecular oxygen, S(3P) + O2(X3Σg−) → SO(X3Σ−) + O(3P), has been determined as (1.7 ± 0.2) × 1012 cm3 mol−s− at 298 °K by means of kinetic spectroscopy in the vacuum ultraviolet region. The source of S(3P) atoms was the isothermal flash photolysis of COS in the presence of Ar or CO2.

The photolysis and pyrolysis of nitromethane and methyl nitrite

1967 ◽  
Vol 299 (1458) ◽  
pp. 317-336 ◽  
Keyword(s):  
Nitric Oxide ◽  
Nitrogen Dioxide ◽  
Elevated Temperatures ◽  
Flash Photolysis ◽  
Stable Form ◽  
Methyl Radicals ◽  
Elimination Reaction ◽  
Kinetic Spectroscopy ◽  
Methyl Nitrite ◽  
A Minor

The photolysis and pyrolysis of nitromethane and methyl nitrite have been studied using the techniques of flash photolysis and kinetic spectroscopy. The results show that photolysis of nitromethane yields methyl radicals and nitrogen dioxide, and that these fragments undergo recombination and disproportionation reactions to form methyl nitrite, methoxyl, and nitric oxide. In the presence of added nitric oxide, the methyl radicals react principally with nitric oxide to form nitrosomethane, which subsequently dimerizes and also reacts further with nitric oxide to yield nitrogen dioxide. The evidence also suggests that nitrosomethane is removed by a relatively efficient reaction with nitrogen dioxide at elevated temperatures to produce nitromethane and nitric oxide. In the case of methyl nitrite, light absorption results not only in photolysis, but also in the formation of an isomer of the nitrite which then reverts slowly to the stable form. The nature of this isomer is not known, but possibilities are suggested and discussed. It is concluded that the decomposition (photolytic or pyrolytic) of methyl nitrite occurs by the rupture of the O—N bond, and that the methoxyl radicals formed disproportionate to yield methanol and form aldehyde. Nitroxyl is also formed but only as a minor product, and the marked increase in intensity of its spectrum in the presence of added nitric oxide shows that it is not formed by a molecular elimination reaction, but probably by CH 3 O + NO → CH 2 O + HNO.

Absorption and flash photolysis kinetic spectroscopy studies on difluoro-, chlorodifluoro-, dichlorofluoro-, and tetrafluorophosphine

1973 ◽  
Vol 77 (9) ◽  
pp. 1126-1128 ◽  
Author(s):  
Edeard G. Skolnik ◽  
Robert J. Salesi ◽  
Charles R. Russ ◽  
P. L. Goodfriend
Keyword(s):  
Flash Photolysis ◽  
Kinetic Spectroscopy ◽  
Spectroscopy Studies

Fluorescence and vibrational relaxation of nitric oxide studied by kinetic spectroscopy

1961 ◽  
Vol 260 (1303) ◽  
pp. 459-474 ◽  
Keyword(s):  
Nitric Oxide ◽  
Vibrational Relaxation ◽  
High Pressures ◽  
Flash Photolysis ◽  
Electronic States ◽  
Analytic Form ◽  
Gas Mixtures ◽  
Inert Gas ◽  
Flash Duration ◽  
Kinetic Spectroscopy

The first excited vibrational level of the ground electronic states of nitric oxide was popu­lated above its equilibrium value by flash photolysis of nitric oxide + inert gas mixtures, under isothermal conditions. Electronic excitation NO 2 II ( v = 0) + hv → NO 2 Ʃ ( v = 0, 1, 2) was followed either by fluorescence NO 2 Ʃ ( v = 0, 1, 2) → NO 2 II ( v = 0, 1, 2...) + hv , or by quenching NO 2 Ʃ ( v = 0, 1, 2) + M → NO 2 II( v = 0, 1, 2...) + M , causing a non-equilibrium population of the vibrational levels of the ground electronic states. Subsequently, the reactions NO 2 II ( v = 1) + M → NO 2 II ( v = 0) + M and NO 2 II ( v = 1) + NO 2 II ( v = 0) → 2NO 2 II ( v = 1) caused a decay of the vibrationally excited molecules with time; this was followed in absorption by kinetic spectroscopy. Because of the rapidity of the last reaction, bands of NO2 II with v >1 were usually observed only in the fluorescence spectrum. In mixtures of 1 to 5 mm of NO with a large excess of nitrogen or krypton, the con­centration of NO2 II ( v = 1) produced by the flash was of the order of 10-1 mm pressure, i. e. about the same concentration which is present in one atmosphere pressure of NO at room temperature. The absolute concentration of NO2 II ( v = 1) was measured accurately by plate photometry, high pressures of NO being used for calibration. The recorded probabilities of vibrational relaxation, P1-0, for NO2 II ( v = 1), and radii for electronic quenching, σ e , by NO, N 2 , CO, H 2 O and CO 2 , are P 1-0 σ e (Å) NO 3.55 x 10 -4 14 N 2 4 x 10 -7 ≤ 2x 10 -2 CO 2.5 x 10 -5 0.6 H 2 O 7 x 10 -3 30 CO 2 1.7 x 10 -4 5 With the use of an analytic form for the flash duration, the entire rise and fall of the concentration of excited species was quantitatively interpreted. A very small fraction of the NO was decomposed by the flash, due either to absorption of radiation below 1900 Å or by reaction of metastable NO molecules with each other or with ground state molecules. Abnormal effects were observed in NO+ H 2 +inert gas mixtures and chemical reaction occurred.

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