The Reaction of the Electronically Excited Oxygen Atom O(1D2) with Nitrous Oxide

1971 ◽  
Vol 49 (11) ◽  
pp. 1808-1817 ◽  
Author(s):  
P. M. Scott ◽  
K. F. Preston ◽  
R. J. Andersen ◽  
L. M. Quick
Keyword(s):  
Oxygen Atom ◽  
Gas Phase ◽  
Room Temperature ◽  
Flash Photolysis ◽  
Excited Atom ◽  
Total Rate ◽  
A Value ◽  
Electronically Excited ◽  
Excited Oxygen

An investigation has been made of the relative importance of the possible pathways [2a]–[2d][Formula: see text]for the reaction in the gas phase at room temperature between the excited oxygen atom O(1D2) and N2O, using the photolysis of NO2, O3, and N2O as sources of the excited atom. Measurement of the yields of N2 and NO from the photolysis at 2288 Å of mixtures of NO2 and N2O has led to a value of 1.01 ± 0.06 for k2a/k2b, the ratio of the rate constants for [2a] and [2b], in excellent agreement with the value of 0.99 ± 0.06 obtained from determination of the yields of N2 and NO2 arising from the flash photolysis of O3–N2O mixtures. The isotopic composition of the N2 produced in the photolysis of 15NO2–N2O mixtures indicated that k2c/k2a < 5 × 10 – 3. Furthermore, the value of k2a/(k2b + k2d) = 1.08 ± 0.19, obtained from a study of the effect of CO2 and Xe additions on the yield of N2 from the photolysis of N2O at 2288 Å, suggests that deactivation [2d] does not make an important contribution to the total rate constant for destruction of O(1D2).

A method for the direct determination of the rate constants for radical-radical interactions in the gas phase II. The rate constant for the recombination of methyl radicals

1957 ◽  
Vol 243 (1232) ◽  
pp. 130-142 ◽  
Keyword(s):  
Gas Phase ◽  
Rate Constant ◽  
Room Temperature ◽  
Direct Determination ◽  
Theoretical Interpretation ◽  
Methyl Radicals ◽  
Gas Phase Reactions ◽  
A Value ◽  
Acetone Vapour

The technique outlined in part I of this paper has been employed to study the photo­sensitized decomposition of acetone vapour. A theoretical interpretation of the non-stationary state applied to non-chain photochemical gas phase reactions with second-order termination has been given and the effects of non-homogeneous absorption of radiation have been considered. A value has been obtained for the rate constant for the recombination of methyl radicals in the gas phase at room temperature.

THE Hg 6(3P1)-PHOTOSENSITIZED DECOMPOSITION OF NITRIC OXIDE

1961 ◽  
Vol 39 (12) ◽  
pp. 2549-2555 ◽  
Author(s):  
Otto P. Strausz ◽  
Harry E. Gunning
Keyword(s):  
Nitric Oxide ◽  
Quantum Yield ◽  
Ground State ◽  
Pressure Range ◽  
Oxides Of Nitrogen ◽  
Total Rate ◽  
A Value ◽  
Electronically Excited ◽  
Static Conditions ◽  
Observed Behavior

The reaction of NO with Hg 6(3P1) atoms has been studied under static conditions at 30°, over the pressure range 1–286 mm. The products were found to be N2, N2O, and higher oxides of nitrogen. At NO pressures exceeding 4 mm, the total rate of formation of N2+N2O was constant, while the ratio N2O/N2 increased linearly with the substrate pressure. The rate was found to vary directly with the first power of the intensity at 2537 Å, and a value of 1.9 × 10−3 moles/einstein was established for the quantum yield of N2 + N2O production. In the proposed mechanism, reaction is attributed to the decomposition of an energy-rich dimer, (NO)2*, which is formed by the collision of electronically excited (4II) NO molecules with those in the ground state. The (NO)2* species is assumed to decompose by the steps: (NO)2* → N2 + O2 and (NO)2* + NO → N2O + NO2. The mechanism satisfactorily explains the observed behavior of the system.

Excited-Atom Production by Electron Bombardment of Alkali-Halides

1986 ◽  
Vol 75 ◽  
Author(s):  
R. E. Walkup ◽  
Ph. Avouris ◽  
A. P. Ghosh
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Ground State ◽  
Excited Atom ◽  
Alkali Halides ◽  
Electron Bombardment ◽  
Secondary Electrons ◽  
Excited Atoms ◽  
Positive Ions ◽  
Electronically Excited

AbstractWe present experimental results which suggest a new mechanism for the production of excited atoms and ions by electron bombardment of alkali-halides. Doppler shift measurements show that the electronically excited atoms have a thermal velocity distribution in equilibrium with the surface temperature. Measurements of the absolute yield of excited atoms, the distribution of population among the excited states, and the dependence of yield on incident electron current support a model in which excited atoms are produced by gas-phase collisions between desorbed ground-state atoms and secondary electrons. Similarly, gas-phase ionization of ground-state neutrals by secondary electrons accounts for a substantial portion of the positive ions produced by electron bombardment of alkali-halides.

scholarly journals Measurements of rate constants of O2(b) quenching by CH4, NO, N2O at temperatures 300-800 K

2018 ◽  
Vol 209 ◽  
pp. 00006
Author(s):  
G.I. Tolstov ◽  
M.V. Zagidullin ◽  
N.A. Khvatov ◽  
I.A. Medvedkov ◽  
A.M. Mebel ◽  
...  
Keyword(s):  
Rate Constants ◽  
Room Temperature ◽  
Quenching Rate ◽  
Important Place ◽  
The Past ◽  
Tunable Dye Laser ◽  
Deactivation Kinetics ◽  
Electronically Excited ◽  
Excited Oxygen ◽  
Good Agreement

Electronically excited oxygen has an important place in the kinetic schemes of the processes taking place in the atmosphere, in the active medium of an oxygen-iodine laser, and in plasma-assisted combustion1. Over the past decades, a large amount of data on the rate constants of quenching O2(b) on a large number of collision partners has been accumulated. However, they mostly refer to the results of measurements at room temperature. In this paper, rate constants for the quenching of O2(b) by collisions with N2O, NO, and CH4 have been determined in the temperature range from 297 to 800 K, by the laser-induced fluorescence method. O2(b) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed via observing the temporal behavior of the b1Σg+→ X3Σg- fluorescence. From the analysis of experimental results, the following temperature dependencies of the quenching rate constants by these gases were obtained, and could be represented by the expressions: kNO=(1.77±0.2)×10-24×T3.5 exp(1138±37/T); kN2O=(2.63±0.14)×10-16×T1.5×exp(590±26/T) and kCH4=(3.54±0.4)×10-18×T1.5×exp(-220±24/T) cm3s-1. All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.

An Overview of Aeronomic Processes in the Stratosphere and Mesosphere

1974 ◽  
Vol 52 (8) ◽  
pp. 1381-1396 ◽  
Author(s):  
M. Nicolet
Keyword(s):  
Nitric Oxide ◽  
Water Vapor ◽  
Nitric Acid ◽  
Oxygen Atom ◽  
Eddy Diffusion ◽  
Atmospheric Conditions ◽  
Hydrogen Atoms ◽  
Electronically Excited ◽  
The Vertical Distribution ◽  
Excited Oxygen

The discrepancy noted between theoretical and observational concentrations of O3 in the mesosphere and stratosphere can be explained by an effect of hydrogen compounds and of nitrogen oxides. Solar radiation dissociates water vapor and methane in the thermosphere and upper mesosphere. In the stratosphere the reaction of the excited oxygen atom O(1D) with methane and nitrous oxide leads to a destruction of these two molecules in the stratosphere which corresponds to a production of carbon monoxide with water vapor and of nitric oxide, respectively. Hydrogen and water vapor molecules also react with the electronically excited oxygen atom O(1D) leading to hydroxyl radicals. Insitu sources of H2 exist in the stratosphere and mesosphere: reaction of OH with CH1, photodissociation of formaldehyde, and also reaction between hydroperoxyl radicals and hydrogen atoms. The vertical distribution of water vapor is not affected by its dissociation in the stratosphere and mesosphere since its reformation is rapid.The ratio of the hydroxyl and hydroperoxyl radical concentrations cannot be determined with adequate precision and complicates the calculation of the destruction of ozone which occurs through reactions of OH and HO2 not only with atomic oxygen at the stratopause but also directly in the middle stratosphere and with CO and NO in the lower stratosphere.In addition to the various reactions involving nitric oxide and nitrogen dioxide, the reactions leading to the production and destruction of nitric acid and nitrous acid must be considered. Nitric acid molecules are involved in an eddy diffusion transport from the lower stratosphere into the troposphere and are, therefore, responsible for the removal of nitric oxide which is produced in the stratosphere. Atmospheric conditions must be known at the tropopause.

scholarly journals Mini-Review: On the Transfer of Nicotine from Tobacco to the Smoker. A Brief Review of Ammonia and “pH” Factors

2000 ◽  
Vol 19 (2) ◽  
pp. 103-113 ◽  
Author(s):  
M Dixon ◽  
K Lambing ◽  
JI Seeman
Keyword(s):  
Gas Phase ◽  
Aqueous Extract ◽  
Federal Trade Commission ◽  
Scientific Literature ◽  
International Organization ◽  
Standardization Method ◽  
Total Rate ◽  
Research Gaps ◽  
Or Efficiency

AbstractA brief review is presented of the scientific literature on the effects of ammonia compounds, when used as tobacco additives, on the smoke chemistry and bioavailablity of nicotine. The review concludes that ammonia compounds used in the manufacture of certain types of tobacco sheet materials:1) contribute to the flavor properties of cigarette smoke,2) do not increase the amount, rate or efficiency of nicotine transferred from tobacco to mainstream smoke (MS),3) do not increase the percentage of nicotine in MS gas phase using the FTC/ISO (Federal Trade Commission/International Organization for Standardization) method,4) have no influence on the determination of MS nicotine yield as measured by the FTC/ISO method, and5) do not increase the total rate or amount of nicotine absorbed by the smoker.The review also examines the use of pH as it relates to tobacco and to smoke and suggests a terminology which more accurately describes the measurement (pH of aqueous extract of tobacco, pH of aqueous extract of smoke, and pH/electrode in smoke). Lastly, a number of research gaps in these areas are identified.

Rates of OH radical reactions. VII. Reactions of OH and OD radicals with n-C4H10, n-C4D10, H2 and D2, and of OH with neo-C5H12 at 297 K

1980 ◽  
Vol 58 (20) ◽  
pp. 2146-2149 ◽  
Author(s):  
George Paraskevopoulos ◽  
Wing S. Nip
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Kinetic Isotope Effect ◽  
Flash Photolysis ◽  
Deuterium Atom ◽  
Oh Radicals ◽  
Confidence Limits ◽  
Kinetic Isotope ◽  
Absorption Technique

Absolute rate constants of hydrogen and deuterium atom abstraction by OH and OD radicals from n-C4H10, n-C4D10, H2 and D2, and by OH radicals from neo-C5H12 have been measured at room temperature in the gas phase using the flash photolysis-resonance absorption technique. The rate constants in units of cm3 mol−1 s−1 were found to be:[Formula: see text]The quoted errors are the 95% confidence limits. A kinetic isotope effect was observed when hydrogen was replaced by deuterium in the paraffin and H2, whereas there was no significant effect when OH was replaced by OD.

Thermal effects in flash photolysis with special reference to Br atom recombination

1968 ◽  
Vol 46 (20) ◽  
pp. 3229-3234 ◽  
Author(s):  
George Burns
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Thermal Effects ◽  
Reaction Rate ◽  
Flash Photolysis ◽  
Reaction Rate Constants ◽  
A Value ◽  
Recombination Rate Constant ◽  
Reaction Vessels

Thermal effects, which accompany flash photolyses, are known to interfere with the determination of reaction rate constants. There are two approximate models currently being used in literature to estimate the magnitude of these effects (1, 8). The first model (1) is the more widely accepted. It is based on the assumption that thermal effects are due to the cooling of reacting gas at the walls of the reaction vessel. The second model (8) is based on the assumption that thermal effects are due to nonuniformity in the concentrations of free radicals produced in flash photolysis; it neglects the heat exchange at the wall of the reaction vessel.It is shown that the second model can be used to calculate the magnitude of thermal effects in reaction vessels of reasonable length. The model was applied to calculate [Formula: see text], the rate constant for the reaction 2Br + Br2 → 2Br2. The value of [Formula: see text], is found to be very sensitive to the choice of model for thermal effects. At room temperature the most reasonable value of [Formula: see text], using the second model, is (4.3 ± 1.3) × 1010 l2 mole−2 s−1. This value agrees very well with independent determinations of [Formula: see text] using a stationary photochemical technique. The first model for treatment of thermal effects (1) was used previously to show that such effects do not influence the measured rates of chemical reactions, and calculations of rate constants using this model have not usually been attempted. In one case (5), however, the first model (1) for thermal effects was employed to calculate a value for [Formula: see text] which was found to be six times larger than our value. Consequently, the second model (8) appears to be a better approximation for quantitative evaluation of thermal effects.Using the raw data (8) and [Formula: see text] = 43 × 109 l2 mole−2 s−1, the value of kAr, the recombination rate constant of Br atoms in excess of argon, was found to be (3.0 ± 0.2) × 109 l2 mole−2 s−1, which agrees well with data available in the literature.

The flash photolysis of phosphine

1961 ◽  
Vol 262 (1308) ◽  
pp. 1-9 ◽  
Keyword(s):  
Excited State ◽  
Gas Phase ◽  
Total Pressure ◽  
Room Temperature ◽  
Flash Photolysis ◽  
Small Particles ◽  
Vibrationally Excited ◽  
Secondary Reactions

The equation representing the decomposition of phosphine by flash photolysis is shown to be PH 3 → P red + 3/2H 2 . The phosphorus is produced in the form of small particles which remain suspended in the gas phase for several minutes provided that the total pressure is high enough. The variation with time of the spectra of PH 2 , PH and P 2 has been studied and the secondary reactions consequent upon the photolysis are shown to be homogeneous. The P 2 is produced in a vibrationally excited state at room temperature, transitions involving levels of up to v' = 7 being observed. A mechanism for the photolysis and the production of excited P 2 is proposed.

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