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.

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 .

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.

The flash photolysis of chlorine monoxide

1957 ◽  
Vol 243 (1232) ◽  
pp. 24-32 ◽  
Keyword(s):  
Chlorine Dioxide ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Reaction Scheme ◽  
Inert Gas ◽  
Short Chain ◽  
Large Excess ◽  
Straight Chain ◽  
Chain Reaction ◽  
Chlorine Monoxide

The flash photolysis of chlorine monoxide in a large excess of inert gas yields chlorine and oxygen, the normal products of photolysis, accompanied by measurable quantities of the ClO radical as an intermediate. The normal and chlorine-sensitized decompositions of chlorine monoxide are studied and a reaction scheme is proposed for the system which has the character of a short-chain reaction with CIO and CI acting as chain carriers. By a study of the decay of the CIO radical and the formation of chlorine dioxide, rate constants are derived for the CIO decay, the production of chlorine dioxide and the straight-chain decomposition of chlorine monoxide by the CIO radical.

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.

Vibrational energy distribution in HF formed by elimination from activated CH3CF3 and CH2CF2

1970 ◽  
Vol 48 (18) ◽  
pp. 2919-2930 ◽  
Author(s):  
P. N. Clough ◽  
J. C. Polanyi ◽  
R. T. Taguchi
Keyword(s):  
Rate Constants ◽  
Vibrational Energy ◽  
Flow System ◽  
Relative Rate ◽  
Elimination Reaction ◽  
Vibrationally Excited ◽  
Vibrational Levels ◽  
Relative Rate Constants ◽  
Fast Flow ◽  
Vibrational Energy Distribution

The combination–elimination reaction CH3 + CF3 → CH3CF3† → CH2CF2 + HF has been studied in a fast-flow system. Infrared chemiluminescence arising from the HF product has been observed from vibrational levels v = 1–4, and relative rate constants, k(v), have been obtained for HF formation in these levels. A study has also been made of the reaction CH2CF2 + Hg*(63P1) → CHCF + HF + Hg(61S0), which has been found to produce vibrationally-excited HF. Relative rate constants k(v) for vibrational levels v = 1–4 have been obtained. It appears that channelling of the potential energy into HF vibration, in the course of the elimination step, is more efficient in the first than in the second of these reactions. In the second reaction HF is eliminated with considerable rotational excitation.

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).

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.

Production of Vibrationally Excited Oxygen Molecules in the Flash Photolysis of Ozone

Nature ◽  
1957 ◽  
Vol 180 (4597) ◽  
pp. 1272-1273 ◽  
Author(s):  
W. D. McGRATH ◽  
R. G. W. NORRISH
Keyword(s):  
Flash Photolysis ◽  
Vibrationally Excited ◽  
Excited Oxygen

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.

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