VIBRATIONAL DISEQUILIBRIUM IN REACTIONS BETWEEN ATOMS AND MOLECULES

1960 ◽  
Vol 38 (10) ◽  
pp. 1769-1779 ◽  
Author(s):  
N. Basco ◽  
R. G. W. Norrish
Keyword(s):  
Hydroxyl Radicals ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Electronic Energy ◽  
Reaction Products ◽  
Energy Distributions ◽  
Vibrationally Excited ◽  
Atoms And Molecules ◽  
New Class ◽  
Excited Oxygen

Observations on the production of vibrationally excited oxygen molecules in the flash photolysis of nitrogen peroxide and of ozone have extended previous work on these systems. In the case of nitrogen peroxide it has been shown that oxygen molecules possessing the entire exothermicity of the reaction in the form of vibrational energy are produced. A new class of reactions is reported in which vibrationally excited hydroxyl radicals are produced under isothermal conditions by the reaction O(1D) + RH → OH* + R, in which the energy for excitation is contributed by the electronic energy of the oxygen atom.These and other cases of non-equilibrated energy distributions in reaction products and theories accounting for this phenomenon are reviewed.

The production of vibrationally excited hydroxyl radicals under isothermal conditions by flash photolysis

1961 ◽  
Vol 260 (1302) ◽  
pp. 293-303 ◽  
Keyword(s):  
Oxygen Atom ◽  
Hydroxyl Radicals ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Hydrogen Abstraction ◽  
Electronic Energy ◽  
Vibrationally Excited ◽  
Isothermal Conditions ◽  
Abstraction Reaction ◽  
Hydrogen Abstraction Reaction

The flash photolysis of ozone in the presence of ammonia, hydrogen, hydrogen chloride, methane and water has been investigated under isothermal conditions. In each case the presence of vibrationally excited hydroxyl radicals has been shown spectroscopically. The concentration of these species is highest at the shortest time (i.e. during the photolysis flash) and decreases rapidly to below detectable limits within about 20 μs. The hydroxyl radical is produced by the reaction O( 1 D ) + HR -> OH + R + 29 to 46 kcal rotationally cold but with up to at least two quanta of vibrational energy, the energy for which is supplied by the electronic energy of the oxygen atom. Under some conditions, the spectrum of oxygen molecules with up to 16 quanta of vibrational energy is also seen and shows that the reaction competes successfully with the hydrogen abstraction reaction. O( 1 D ) + O 2 -> O 2 * + O 2 competes successfully with the hydrogen abstraction reaction.

Energy disequilibrium in the flash photolysis of NO 2

1973 ◽  
Vol 334 (1599) ◽  
pp. 553-568 ◽  
Keyword(s):  
Nitric Oxide ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Dissociation Limit ◽  
Primary Process ◽  
Transfer Energy ◽  
Vibrationally Excited ◽  
Absolute Concentrations ◽  
The Absolute ◽  
Excited Oxygen

From measurements of the absolute concentrations of vibrationally excited oxygen produced in levels v" = 4 to v" = 13, it is concluded that ca . 20 % of the exothermicity of the reaction O( 3 P) + NO 2 → NO + O + 2 ( v" ≤11) (1) appears initially as vibrational energy in oxygen. Vibrationally excited nitric oxide ( v" = 1, 2) is also observed and may be produced in this reaction or in the primary process NO 2 + hv → NO ( v" ≤ 2) + O( 3 P). More highly excited oxygen ( v" ≤ 15), with energy exceeding the exothermicity of the reaction, is produced in reaction (1) when the NO 2 is first excited by radiation above the dissociation limit near 400 nm. The excited NO 2 thus produced can also transfer energy to nitric oxide. NO 2 * + NO( v" = 0) → NO 2 + NO( v" = 1).

The study of energy transfer by kinetic spectroscopy I. The production of vibrationally excited oxygen

1956 ◽  
Vol 233 (1195) ◽  
pp. 455-464 ◽  
Keyword(s):  
Flash Photolysis ◽  
Vibrational Energy ◽  
Vibrationally Excited ◽  
Near Resonance ◽  
Vibrational Levels ◽  
Great Excess ◽  
First Time ◽  
Kinetics Of ◽  
Excited Oxygen ◽  
Electronic Ground

The flash photolysis of chlorine dioxide or of nitrogen dioxide in a great excess of inert gasyields oxygen molecules in their electronic ground states with up to eight quanta of vibrational energy. By a study of the reaction kinetics of the two systems, it is concluded that these excited molecules have their origin in the reactions O + NO 2 = NO + O 2 and O + CIO 2 = CIO + O 2 respectively. Thus, for the first time we have available a very convenient method of studying the collisional transfer and degradation of vibrational energy from molecules in the higher vibrational levels of the ground state and some preliminary measurements of the efficiency of deactivation by various molecules are given. It is concluded that the energy is removed most readily either when there is near resonance of the vibrational levels with those of the oxygen, or by free radicals. Some of the reactions of the chlorine oxides present are also discussed.

Studies of the reactions of excited oxygen atoms and molecules produced in the flash photolysis of ozone

1960 ◽  
Vol 254 (1278) ◽  
pp. 317-326 ◽  
Keyword(s):  
Flash Photolysis ◽  
Vibrational Energy ◽  
Oh Radicals ◽  
Chain Reaction ◽  
Vibrationally Excited ◽  
Detailed Mechanism ◽  
Photolytic Decomposition ◽  
Excited Oxygen ◽  
Electronic Ground ◽  
Oxygen Atoms

The photolytic decomposition of ozone has been further investigated using the technique of flash photolysis. Earlier results have been extended and a detailed mechanism for the production of vibrationally excited oxygen molecules put forward. Comparative studies of the decomposition with and without traces of water present have shown that the 1 D oxygen atom must be responsible for the chain reaction in both cases. When dry ozone is photolyzed under isothermal conditions, absorption due to vibrationally excited oxygen molecules in their electronic ground states is detected. These molecules are produced by the reaction O + O 3 → O* 2 + O 2 with up to 17 quanta of vibrational energy, and are rotationally cold. When water is present, however, no absorption due to O* 2 occurs but strong OH absorption is seen and it is shown that OH radicals are responsible for propagating the chain reaction in this case. These radicals can only be formed by the reaction O( 1 D ) + H 2 O → 2OH + O 2 , leading to chain branching. It is an interesting observation that this reaction must be preferred to that with ozone stated above. This conclusion will be examined later. Reactions of 1 D oxygen atoms with fluorine, chlorine, bromine and hydrogen have also been investigated.

Reactions of halogen oxides studied by flash photolysis IV. Vacuum ultraviolet kinetic spectroscopy studies on chlorine dioxide

1974 ◽  
Vol 336 (1607) ◽  
pp. 495-505 ◽  
Keyword(s):  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Heat Of Reaction ◽  
Rydberg Series ◽  
Vibrationally Excited ◽  
Extinction Coefficients ◽  
Spectroscopy Studies ◽  
Halogen Oxides ◽  
Excited Oxygen

The rate constants for the production of vibrationally excited oxygen in the reactions O + CIO 2 -----» O 2 (v''≤ 15) + CIO O + CIO -----» O 2 (v''≤ 14) + Cl are approximately equal for all values of v" ≤ 13. The oxygen initially receives 45+10% of the heat of reaction in the form of vibrational energy. Extinction coefficients have been measured for several bands of the C-X, D -X and E -X systems of CIO 2 in the vacuum ultraviolet. Five new systems are reported between 141 and 128 nm. Two of these, F-X and J-X , and the C-X system form a Rydberg series for an ionization potential of 10.36 eV.

Vibrational Energy Transfer in Carbon Monoxide

1972 ◽  
Vol 50 (9) ◽  
pp. 889-897 ◽  
Author(s):  
P. H. Dawson ◽  
W. G. Tam
Keyword(s):  
Energy Exchange ◽  
Vibrational Energy ◽  
Transverse Flow ◽  
Vibration Energy ◽  
Excess Oxygen ◽  
Experimental Measurements ◽  
Energy Distributions ◽  
Vibrationally Excited ◽  
Population Distributions

The role of V–V processes in vibrationally excited CO systems in the longitudinal and transverse flow chemical lasers is studied. Initial vibrational energy distributions of CO formed by the O + CS reaction are deduced from chemiluminescent data using calculated values of the vibration energy exchange probabilities. The time evolution of the population distributions is then obtained by computer simulation. The results are compared with experimental measurements. The effects of excess oxygen and of "cold" CO on the population distributions are also discussed.

Reactions of halogen oxides studied by flash photolysis II. The flash photolysis of chlorine monoxide and of the ClO free radical

1971 ◽  
Vol 323 (1554) ◽  
pp. 401-415 ◽  
Keyword(s):  
Free Radical ◽  
Quantum Yield ◽  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Vibrationally Excited ◽  
Chlorine Atoms ◽  
Chlorine Monoxide ◽  
Halogen Oxides ◽  
Excited Oxygen

A study of the flash photolysis of chlorine monoxide and of its photosensitized decomposition by chlorine and bromine has yielded rate constants for the reactions Cl + Cl 2 O → Cl 2 + ClO, k 1 = 4.1 x 10 8 l mol -1 s -1 , Br + Cl 2 O → BrCl + ClO, k 9 = 6.1 x 10 8 l mol -1 s -1 , ClO + Cl 2 O → ClO 2 + Cl 2 , k 3 = 2.6 x 10 5 l mol -1 s -1 , ClO + Cl 2 O → Cl 2 + O 2 + Cl, k 4 = 6.5 x 10 5 l mol -1 s -1 , 2ClO → Cl 2 + O 2 , k 2 = 2.8 x 10 7 l mol -1 s -1 . The quantum yield for the decomposition of chlorine monoxide was measured in each of the three systems and is quantitatively accounted for by the reactions given. The CIO free radical has been flash photolysed and the production of vibrationally excited oxygen in the reaction O + CIO → Cl + O* 2 ( v" ≼ 14), k 11 = 7.5 x 10 9 l mol -1 s -1 demonstrated. The same reaction is responsible for the production of O* 2 in the flash photo­lysis of Cl 2 O with radiation below ~ 300 nm. The relaxation of O* 2 by chlorine atoms is exceptionally efficient, with a rate constant for v" = 12 in excess of 2 x 10 9 l mol -1 s -1 . The corresponding rate constant for relaxation by Cl 2 O is < 10 8 l mol -1 s -1 .

The e.p.r. spectrum of vibrationally excited hydroxyl radicals

1971 ◽  
Vol 323 (1555) ◽  
pp. 541-554 ◽  
Keyword(s):  
Gas Phase ◽  
Hydroxyl Radicals ◽  
Hyperfine Coupling ◽  
Vibrational Energy ◽  
Theoretical Calculations ◽  
Coupling Constants ◽  
Hydrogen Atoms ◽  
Vibrationally Excited ◽  
The Matrix ◽  
Van Vleck

The e. p. r. spectrum of vibrationally excited hydroxyl radicals in levels v = 1, 2, 3 and 4 of the 2 II 3/2 ground state has been observed in the reaction between hydrogen atoms and ozone in the gas phase. Although the variation of ∧ -doubling with vibrational energy superficially agrees well with the ‘pure precession’ model of Van Vleck, there is clear evidence that the matrix element <II│ L y │ ∑> decreases considerably with increasing internuclear distance. The form of the decrease in the hyperfine coupling constants with increasing vibrational energy agrees well with that deduced from Kayama’s theoretical calculations.

Reactions of halogen oxides studied by flash photolysis. I. The flash photolysis of chlorine dioxide

1971 ◽  
Vol 323 (1552) ◽  
pp. 29-68 ◽  
Keyword(s):  
Chlorine Dioxide ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Vibrationally Excited ◽  
Extinction Coefficients ◽  
Chlorine Monoxide ◽  
Vibrational Levels ◽  
Halogen Oxides ◽  
Excited Oxygen

The production and decay of the CIO radical and of vibrationally excited oxygen following the isothermal flash photolysis of chlorine dioxide has been studied. From their dependence on flash energy and from the effects of added chlorine, oxygen and chlorine monoxide on the system, the following mechanism and rate constants are proposed: CIO 2 + hv → CIO + O 2CIO → CI 2 + O 2 K 1 = 2.7 x 10 7 l mol -1 s -1 O + CIO 2 → CIO + O 2 * ( v " ≼ 15) k 3 = 3.0 x 10 10 l mol -1 s -1 O + CIO → CI + O 2 * ( v " ≼ 14) k 4 = 7.0 x 10 9 l mol -1 s -1 CIO (CIO 2 ) + O 2 * ( v " = n ) → CIO (CIO 2 ) + O 2 * ( v " < n ) k 10 ( v " = 12) = 2 x 10 8 l mol -1 s -1 CI + O 2 * ( v " = n ) → CI + O 2 * ( v " < n ) k 11 ( v " = 12) = 7 x 10 9 l mol -1 s -1 O + O 2 * ( v " = n ) → O + O 2 * ( v " < n ) k 12 ( v " = 12) = 2 x 10 10 l mol -1 s -1 O + Cl 2 O → 2CIO k 6 = 5.2 x 10 9 l mol -1 s -1 The rate constants k 10 , k 11 and k 12 for O 2 * (v" = 6) and the relative values of k 3 for various vibrational levels have also been measured. Studies of the flash photolysis of mixtures of chlo­rine monoxide and chlorine dioxide and of chlorine and oxygen have yielded values of k 1 in agreement with that given above. The extinction coefficients of the CIO radical at 257.7, 277.2 and 292 nm were found to be 1150, 1700 and 1050 l mol -1 cm -1 respectively.

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