The flash photolysis of ozone

1957 ◽  
Vol 242 (1230) ◽  
pp. 265-276 ◽  
Keyword(s):  
Electronic State ◽  
Vibrational Energy ◽  
Inert Gases ◽  
Inert Gas ◽  
Ground Electronic State ◽  
Explosive Decomposition ◽  
Kcal Mole ◽  
Vibrationally Excited ◽  
Energy Chain ◽  
Excited Oxygen

The photolytic decomposition of ozone in ultra-violet radiation has been studied by kinetic spectroscopy. It has been shown that vibrationally excited oxygen in its ground electronic state plays a most important part in the decomposition. These molecules have sufficient vibrational energy to bring about dissociation of ozone, thus regenerating oxygen atoms which can again produce vibrationally excited oxygen. The importance of this energy chain is emphasized by comparative studies on the explosive decomposition of pure ozone, and the isothermal decomposition when an excess of inert gas is present. In the former case the O* 2 is removed so rapidly, mainly by reaction with ozone, that no absorption due to it can be detected. Using an excess of inert gas to obtain isothermal conditions it has been possible to observe Schumann–Runge absorption of oxygen molecules in their ground electronic state, with up to 16 quanta of vibrational energy. The vibrational energy distribution of the oxygen molecules formed has an apparent maximum at v " = 13 (53.5 kcal/mole) and falls off sharply at v " = 12 and 16 (49.0 and 63.2 kcal/mole). It is shown that the only reasonable reaction for the production of excited oxygen is O + O 3 → O* 2 + O 2 . Studies on the rate of ozone decay with time have also been carried out and the results analyzed in terms of the rate constants of reactions involving the deactivation of excited oxygen and the three-body recombination O + O 2 + M → O 3 + M . It is shown that the spherically symmetrical and chemically inert gases such as A, He and SF 6 are much less efficient in bringing about recombination than N 2 , N 2 O or CO 2 .

Vibrational energy transfer. Collisional quenching of competitive unimolecular reactions

1968 ◽  
Vol 46 (2) ◽  
pp. 341-343 ◽  
Author(s):  
D. C. Tardy ◽  
C. W. Larson ◽  
B. S. Rabinovitch
Keyword(s):  
Vibrational Energy ◽  
Heat Bath ◽  
Polyatomic Molecules ◽  
Unimolecular Reaction ◽  
Collisional Quenching ◽  
Kcal Mole ◽  
Vibrationally Excited ◽  
Reaction Systems ◽  
A Value ◽  
Collisional Deexcitation

A technique is described for the study of collisional deexcitation of highly vibrationally excited polyatomic molecules by use of externally activated competitive unimolecular reaction systems. This method has some advantages and is illustrated by the decomposition of chemically activated hexyl-3 radicals in the presence of H2 and CF4 as heat bath molecules. The former removes ~1.2 kcal mole−1 per successful collision; while for the latter a value in excess of 4.6 kcal is found so that CF4 behaves operationally like a strong collider.

AN IMPROVED TECHNIQUE FOR THE OBSERVATION OF INFRARED CHEMILUMINESCENCE: RESOLVED INFRARED EMISSION OF OH ARISING FROM THE SYSTEM H + O2

1960 ◽  
Vol 38 (10) ◽  
pp. 1742-1755 ◽  
Author(s):  
P. E. Charters ◽  
J. C. Polanyi
Keyword(s):  
Infrared Spectrum ◽  
Electronic State ◽  
Vibrational Temperature ◽  
Infrared Emission ◽  
Multiple Reflection ◽  
Ground Electronic State ◽  
Oh Radicals ◽  
Vibrationally Excited ◽  
Improved Technique ◽  
First Time

A multiple reflection apparatus for the observation of infrared chemiluminescence is described. By means of this apparatus infrared emission from the system H + O2 has been identified as being due to vibrationally excited OH radicals in levels v = 1, 2, and 3 of the ground electronic state. The resolved infrared spectrum of the OH fundamental has been observed for the first time without interference from other emission. The most likely source of excited OH is the reaction H + HO2 → OH† + OH. The vibrational 'temperature' of OH† (vibrationally excited OH in its ground electronic state) in our system is in the region of TV = 2240 °K. These findings are discussed in relation to Krassovsky's suggestion that reaction between H and O2 could account for the Meinel hydroxyl bands in the night sky.

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).

scholarly journals Collisional relaxation of apocarotenals: identifying the S* state with vibrationally excited molecules in the ground electronic state S0*

2015 ◽  
Vol 17 (16) ◽  
pp. 10478-10488 ◽  
Author(s):  
Florian Ehlers ◽  
Mirko Scholz ◽  
Jens Schimpfhauser ◽  
Jürgen Bienert ◽  
Kawon Oum ◽  
...  
Keyword(s):  
Electronic State ◽  
Ground Electronic State ◽  
Collisional Relaxation ◽  
Vibrationally Excited ◽  
Vibrationally Hot Molecules ◽  
Excited Molecules

The S* signal of carotenoids corresponds to vibrationally hot molecules in the ground electronic state S0*.

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.

Infra-red chemiluminescence I. Infra-red emission from hydrogen chloride formed in the systems atomic hydrogen plus chlorine, atomic hydrogen plus hydrogen chloride, atomic hydrogen plus deuterium chloride, and atomic deuterium plus hydrogen chloride

1960 ◽  
Vol 258 (1295) ◽  
pp. 529-563 ◽  
Keyword(s):  
Electronic State ◽  
Hydrogen Chloride ◽  
Atomic Hydrogen ◽  
Room Temperature ◽  
Ground Electronic State ◽  
Third Body ◽  
Vibrationally Excited ◽  
Red Emission ◽  
Vibrational Levels ◽  
Infra Red

Infra-red emission arising from several room-temperature gas-phase reactions has previously been described by the authors in preliminary communications (Cashion & Polanyi 1958, 1959 a, b, c ). In the present work, details of this new technique are given. Spectra obtained from the systems H + Cl 2 , H + HCl, H + DCl and D + HCl are described. These consist of the resolved spectra of the HCl fundamental transitions (∆ v = 1) in the ground electronic state, the partially resolved first overtones (∆ v = 2) and, in one system, the unresolved second overtones (∆ v = 3). The system H + Cl 2 gives rise to emission from all vibrational levels up to and including v = 6; the system H + HCl from all levels up to and including v = 7. A detailed examination of the spectra obtained from the systems H + HCl, H + DCl and D + HCl leads to the conclusion that these emissions arise from the formation of vibrationally excited HCl or DCl as the product of an association reaction between hydrogen atoms and chlorine atoms (in the presence of some ‘third body’, M ). This result constitutes the first direct evidence for the view that association reactions lead to the formation of highly vibrating molecules (Polanyi 1959). Also consistent with this view is the observation made here that HCl or DCl acting as a third body in association reactions is not excited to levels higher than v = 1. The bulk of the emission observed from the system H + Cl 2 is believed to arise from the exchange reaction H + Cl 2 = HClꜛ v ≼ 6 + Cl (where HClꜛ is vibrationally excited HCl in its ground electronic state). The vibrational distribution of HClꜛ in the system H + Cl 2 , under our experimental conditions, conforms approximately to a Boltzmann distribution for a vibrational temperature of 2700°K. From this observed distribution a calculation of the initial distribution is made, which would indicate that the HClꜛ are formed initially in all accessible vibrational levels, lower levels being favoured over higher. However, this result is based on the arbitrary assumption that vibrational-vibrational exchange between HClꜛ molecules is negligible. The distribution of HClꜛ among rotational levels of v = 1 in the system H + Cl 2 is definitely non-Boltzmann. The excess rotational energy over room temperature equilibrium energy, is shown to come from an even greater excess present in the HClꜛ as originally formed. The absolute intensity of the emission is calculated at ca . 0.005 W. It is estimated that roughly 1 to 10 % of the heat of reaction goes into vibrational excitation.

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.

scholarly journals The Populations of H2 Vibrational States in Intense UV Fields Near O-B Stars

1987 ◽  
Vol 115 ◽  
pp. 179-180
Author(s):  
P. E. Dewdney ◽  
R. S. Roger ◽  
N. Robert
Keyword(s):  
Electronic State ◽  
Excited States ◽  
Ground State ◽  
Molecular Hydrogen ◽  
Ground Electronic State ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
B Stars ◽  
Intense Fields ◽  
The Mean

In most places where molecular hydrogen exists in the interstellar medium, it will be found in the ground vibrational and ground electronic state. This will not be so, however, near 0 or early B stars where, in the region just beyond the ionization boundary, populations will be determined by UV fields up to 105 times more intense than the mean interstellar value (4 × 10−16 ergs cm−3 s−1 = 1 Habing unit). The H2 absorbs Lyman-Werner band photons longwards of λ91 nm and subsequent decays to the ground electronic state may lead to dissociation (vibrational continuum) or to one of 14 vibrationally excited states. Molecules in these states have lifetimes of order 1010 s and, in the intense fields, will be exposed to further Lyman-Werner excitation. The probability of dissociation is therefore greatly enhanced by this ‘multiple excitation’, since the number of lines available to vibrationally excited H2 is many times that available to ground-state H2 (Shull, 1978).

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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