scholarly journals THE STUDY OF ELECTRICALLY DISCHARGED O2 BY MEANS OF AN ISOTHERMAL CALORIMETRIC DETECTOR

1959 ◽  
Vol 37 (10) ◽  
pp. 1680-1689 ◽  
Author(s):  
L. Elias ◽  
E. A. Ogryzlo ◽  
H. I. Schiff
Keyword(s):  
Gas Phase ◽  
Molecular Oxygen ◽  
Surface Recombination ◽  
Negative Temperature ◽  
Recombination Coefficient ◽  
Third Order ◽  
Atom Concentration ◽  
Electrodeless Discharge ◽  
First Order ◽  
A Value

Molecular oxygen was subjected to an electrodeless discharge in the pressure range 0.1–3 mm Hg. The oxygen atom concentration was measured as a function of time in a flow system by means of a movable atom detector which consisted of a platinum wire coated with a suitable catalyst for atom recombination. The atom concentration was calculated from the heat liberated when the detector was operated under isothermal conditions. The surface recombination was found to be first order in the atom concentration. A value of 7.7 × 10−5 was obtained for the recombination coefficient (γ) on Pyrex. No temperature dependence for γ was observed. The gas phase recombination of oxygen atoms was found to be consistent with the mechanism[Formula: see text]The rate constant for the third-order reaction was found to have a value of 1.0 × 1014 cc2 mole−2 sec−1, and a small negative temperature dependence.Evidence was also obtained for the presence of considerable amounts of excited molecular oxygen in electrically activated O2.

The formation of O2(a1Δg) in homogeneous and heterogeneous atom recombination

1986 ◽  
Vol 64 (12) ◽  
pp. 1614-1620 ◽  
Author(s):  
A. A. Ali ◽  
E. A. Ogryzlo ◽  
Y. Q. Shen ◽  
P. T. Wassell
Keyword(s):  
Kinetic Study ◽  
Gas Phase ◽  
Molecular Oxygen ◽  
Rate Constant ◽  
Room Temperature ◽  
High Efficiency ◽  
Flow System ◽  
Order Reaction ◽  
Third Order ◽  
First Order

The recombination of oxygen atoms has been studied in a discharge flow system at room temperature. The yield of O2(a1Δg) in the recombination on Pyrex has been found to be 0.08 (±0.02). In the gas phase, O2(a) was found to be formed in a process that is second order in [O] and first order in [N2]. The rate constant for this third-order reaction was found to be 3.4 (±0.4) × 10−34 cm6∙molecule−2∙s−1, representing a yield of 0.07 (±0.02). In the presence of molecular oxygen, the rate of production of O2(a) was found to increase. A kinetic study of this effect led to the conclusion that collisions of molecular oxygen with an unidentified precursor can produce O2(a) with high efficiency.

The Role of Starting Potential in the Kinetics of Chemical Reactions under Electrodeless Discharge

1970 ◽  
Vol 25 (11) ◽  
pp. 1772
Author(s):  
T.S.R Ao ◽  
A. Patil
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Electric Discharge ◽  
Specific Rate ◽  
Gas Phase Reactions ◽  
Electrodeless Discharge ◽  
First Order ◽  
Kinetics Of

Abstract It has been shown that in kinetically first order gas phase reactions occuring under electric discharge, such as the decomposition of N2O, the application, at various initial pressures, of the same multiple of the respective starting potential ensures that the reaction occurs at the same specific rate.

Polydiene Oxidations with Singlet Oxygen

1972 ◽  
Vol 45 (2) ◽  
pp. 423-436 ◽  
Author(s):  
M. L. Kaplan ◽  
P. G. Kelleher
Keyword(s):  
Singlet Oxygen ◽  
Gas Phase ◽  
Molecular Oxygen ◽  
Ground State ◽  
Homogeneous Solution ◽  
Surface Oxidation ◽  
Electrodeless Discharge ◽  
Photosensitized Oxidation

Abstract Excited molecular oxygen in its singlet delta (1Δg) state can be made chemically in homogeneous solution and in the gas-phase by the electrodeless discharge of ground state oxygen. Both techniques have been used to perform oxidations of polydiene systems. Solutions of high cis, trans, and vinyl polybutadienes have been treated with singlet oxygen produced in situ. Only the high cis and high trans were oxidized, apparently by different mechanisms. Squalene, a model for polyisoprene, has been oxidized in solution and the initially formed hydroperoxides reduced and analyzed and found identical to the product from a photosensitized oxidation. Cis-polybutadiene films were treated with gas-phase singlet oxygen and the extent of surface oxidation was monitored spectroscopically and chemically.

Rates of elementary processes in the chain reaction between hydrogen and oxygen II. Kinetics of the reaction of hydrogen atoms with molecular oxygen

1963 ◽  
Vol 275 (1363) ◽  
pp. 559-574 ◽  
Keyword(s):  
Molecular Oxygen ◽  
Kinetic Studies ◽  
Negative Temperature ◽  
Product Analysis ◽  
Hydrogen Atoms ◽  
The Third ◽  
Rate Determining Step ◽  
A Value ◽  
Explosion Limit ◽  
Kinetics Of

The addition of molecular oxygen was found to increase the rate of rem oval of hydrogen atoms in a flow system at and below room temperature. Kinetic studies of this process using argon carrier showed that the rate-determining step is the third-order reaction H + O2 + Ar = HO 2 + Ar. (2) Atomic oxygen in small concentrations is produced in the system. Product analysis and measurements of oxygen atom concentrations indicated that the principal reactions removing HO 2 under these conditions are H+HO 2 = H 2 +O 2 , (12a) H+HO 2 = OH+OH, (12b) H+HO 2 = H 2 O+O 2 , (12c) A value for k 2 of 2.2 x 10 -32 cm 6 molecule -2 s -1 was determined at 293 °K. Reaction (2) was found to have a small negative temperature coefficient. These data and values of k 2 from explosion limit studies can be represented by the expression k 2 = 1.3 x 10 -33 exp (+ 1600 + 700/ RT ) cm 6 molecule -2 s -1 in the range 250 to 800 °K. The third-body efficiencies in reaction (2) at 293 °K of He and H 2 O relative to Ar are similar to those obtained from data on the second explosion limit at higher temperatures.

scholarly journals Rate coefficients for the gas-phase reaction of OH with <i>Z</i>-3-hexen-1-ol, 1-penten-3-ol, <i>E</i>-2-penten-1-ol, and <i>E</i>-2-hexen-1-ol between 243 and 404 K

2011 ◽  
Vol 11 (1) ◽  
pp. 2377-2405 ◽  
Author(s):  
M. E. Davis ◽  
J. B. Burkholder
Keyword(s):  
Gas Phase ◽  
Negative Temperature ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Phase Reaction ◽  
Oh Radical ◽  
Gas Phase Reaction ◽  
First Order ◽  
Unsaturated Alcohols ◽  
Temperature Dependences

Abstract. Rate coefficients, k, for the gas-phase reaction of the OH radical with (Z)-3-hexen-1-ol ((Z)-CH3CH2CH=CHCH2CH2OH). (k1), 1-penten-3-ol (CH3CH2CH(OH)CH=CH2) (k2), (E)-2-penten-1-ol ((E)-CH3CH2CH=CHCH2OH) (k3), and (E)-2-hexen-1-ol ((E)-CH3CH2CH2CH=CHCH2OH) (k4), unsaturated alcohols that are emitted into the atmosphere following vegetation wounding, are reported. Rate coefficients were measured under pseudo-first-order conditions in OH over the temperature range 243–404 K at pressures between 20 and 100 Torr (He) using pulsed laser photolysis (PLP) to produce OH radicals and laser induced fluorescence (LIF) to monitor the OH temporal profile. The obtained rate coefficients were independent of pressure with negative temperature dependences that are well described by the Arrhenius expressions k1(T) = (1.3 ± 0.1) × 10−11 exp[(580 ± 10)/T]; k1(297K) = (1.06 ± 0.12) × 10−10 k2(T) = (6.8 ± 0.7) × 10−12 exp[(690 ± 20)/T]; k2(297K) = (7.12 ± 0.73) × 10−11 k3(T) = (6.8 ± 0.8) × 10−12 exp[(680 ± 20)/T]; k3(297K) = (6.76 ± 0.70) × 10−11 k4(T) = (5.4 ± 0.6) × 10−12 exp[(690 ± 20)/T]; k4(297K) = (6.15 ± 0.75) × 10−11 (in units of cm3 molecule−1 s−1). The quoted uncertainties are at the 2σ (95% confidence) level and include estimated systematic errors. The rate coefficients obtained in this study are compared with literature values where possible.

scholarly journals Rate coefficients for the gas-phase reaction of OH with (<i>Z</i>)-3-hexen-1-ol, 1-penten-3-ol, (<i>E</i>)-2-penten-1-ol, and (<i>E</i>)-2-hexen-1-ol between 243 and 404 K

2011 ◽  
Vol 11 (7) ◽  
pp. 3347-3358 ◽  
Author(s):  
M. E. Davis ◽  
J. B. Burkholder
Keyword(s):  
Gas Phase ◽  
Negative Temperature ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Phase Reaction ◽  
Oh Radical ◽  
Gas Phase Reaction ◽  
First Order ◽  
Unsaturated Alcohols ◽  
Temperature Dependences

Abstract. Rate coefficients, k, for the gas-phase reaction of the OH radical with (Z)-3-hexen-1-ol (Z)-CH3CH2CH = CHCH2CH2OH) (k1), 1-penten-3-ol (CH3CH2CH(OH)CH = CH2) (k2), (E)-2-penten-1-ol ((E)-CH3CH2CH = CHCH2OH) (k3), and (E)-2-hexen-1-ol ((E)-CH3CH2CH2CH = CHCH2OH) (k4), unsaturated alcohols that are emitted into the atmosphere following vegetation wounding, are reported. Rate coefficients were measured under pseudo-first-order conditions in OH over the temperature range 243–404 K at pressures between 20 and 100 Torr (He) using pulsed laser photolysis (PLP) to produce OH radicals and laser induced fluorescence (LIF) to monitor the OH temporal profile. The obtained rate coefficients were independent of pressure with negative temperature dependences that are well described by the Arrhenius expressions k1(T) = (1.3 ± 0.1) × 10−11 exp[(580 ± 10)/T]; k1(297 K) = (1.06 ± 0.12) × 10−10 k2(T) = (6.8 ± 0.7) × 10−12 exp[(690 ± 20)/T]; k2(297 K) = (7.12 ± 0.73) × 10−11 k3(T) = (6.8 ± 0.8) × 10−12 exp[(680 ± 20)/T]; k3(297 K) = (6.76 ± 0.70) × 10−11 k4(T) = (5.4 − 0.6) × 10−12 exp[(690 ± 20)/T]; k4(297 K) = (6.15 ± 0.75) × 10−11 (in units of cm3 molecule−1 s−1). The quoted uncertainties are at the 2σ (95% confidence) level and include estimated systematic errors. The rate coefficients obtained in this study are compared with literature values where possible.

Kinetics and Temperature Dependence of the Hydration of NO+ in the Gas Phase

1973 ◽  
Vol 51 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Margaret A. French ◽  
L. P. Hills ◽  
P. Kebarle
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Transfer Reaction ◽  
Negative Temperature ◽  
Ion Source ◽  
Third Order ◽  
The Third ◽  
Kinetics Of

The kinetics of the atmospherically important hydration sequence: NO+(H2O)n−1 + H2O = NO+(H2O)n and the transfer reaction NO+(H2O)n + H2O = HNO2 + H+(H2O)n were examined in nitrogen containing small quantities of NO and H2O with a pulsed high pressure ion source mass spectrometer. The room temperature mechanism and rate constants were found to be in agreement with earlier work in other laboratories. The temperature dependence of the reaction was examined for the range 27–157 °C. The transfer reaction does not occur at higher temperatures so that the NO+ hydration equilibria for n = 1 and 2 could be measured leading to ΔH1,0 = 18.5 and ΔH2,1 = 16.1 kcal/mol. The third order forward clustering rate constants were found to have negative temperature coefficients.

Gas phase ion equilibria: heats of formation of acylium ions RCO+ and protonated acids RC(OH)2+; gas phase catalysis of proton shift RC(OH)2+ → RCO(OH2)+

1979 ◽  
Vol 57 (24) ◽  
pp. 3205-3215 ◽  
Author(s):  
W. R. Davidson ◽  
S. Meza-Höjer ◽  
P. Kebarle
Keyword(s):  
Gas Phase ◽  
Negative Temperature ◽  
Ion Source ◽  
Activation Energy Barrier ◽  
Third Order ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
Proton Shift ◽  
Gas Phase Ion ◽  
Good Agreement

The equilibria [2]: [Formula: see text] for R = CH3, C2H5, and C6H5 were studied in a pulsed electron beam high ion source pressure mass spectrometer. van't Hoff plots led to ΔH2 values: (CH3), 24.6; (C2H5), 22.7; (C6H5), 21.9 kcal/mol. ΔHf(RC(OH)2+) were obtained from gas phase basicity ladders combined with the new ΔHf(t-butyl+) = 163 kcal/mol (Beauchamp). The ΔHf(RC(OH)2+) were: (CH3), 71.3; (C2H5), 63.6; (C6H5), 95.5 kcal/mol. Combination of ΔH2 with ΔHf(RC(OH)2+) leads to ΔHf(RCO+): (CH3), 153.7; (C2H5), 144; (C6H5), 174.6 kcal/mol. These results are in agreement with selected data from appearance potentials. The energies and structures of the participants in reaction [2] were calculated by MINDO/3 and STO-3G. MINDO/3 gave good agreement with ΔH2. The establishment of the equilibria [2] was unusually slow. A study of the kinetics revealed that k2f is approximately third order, unusually small, and has an unusually large negative temperature coefficient. Furthermore, reaction [2] was found to be catalyzed by RCOOH. An explanation of these observations is given by assuming that the proton shift RCO(OH2)+ → RC(OH)2+ has a large activation energy barrier in the gas phase. This barrier is removed by formation of a hydrogen bonded complex with RCOOH.

The recombination of nitrogen atoms and the nitrogen afterglow

1967 ◽  
Vol 296 (1445) ◽  
pp. 201-221 ◽  
Keyword(s):  
Molecular Nitrogen ◽  
Absolute Intensity ◽  
Partial Replacement ◽  
Surface Process ◽  
Third Order ◽  
First Order ◽  
A Value ◽  
State Measurement ◽  
Fast Flow ◽  
Catalytic Recombination

The recombination of nitrogen atoms has been studied photometrically in a fast flow system. The concentration of nitrogen atoms was determined by nitric oxide titration. The measured bimolecular rate constant has the form k B = A + B[M] for M = N 2 , Ar and He with a constant value of A . The surface process was proved to be second order by inducing a small first order catalytic recombination involving CN and showing by computer analysis that a first order surface process would have been measured readily in our system. Third order rate constants (expressed as d[N 2 ]/d t ) had values: k N 2 = k Ar = (1.38 ± 0.11) × 10 15 , k He = (1.92 ± 0.18) × 10 15 in cm 6 mole –2 s –1 units at 298 °K. The surface process in the 26 mm i. d. flow tube had a value of (4.4 ± 0.1) × 10 8 cm 3 mole –1 s –1 at 298 °K. In the range 196 to 327 °K, activation energies were –(975 ± 140) cal/mole for the homogeneous process and +(620 ± 50) cal/mole for the surface reaction. The intensity of the nitrogen afterglow was shown to be proportional to [N] 2 and inde­pendent of total pressure for nitrogen carrier in the range 2 to 10 mmHg. Partial replacement of the nitrogen carrier by helium or argon enhanced the nitrogen afterglow on a mole fraction basis. This effect was shown to be associated with an efficient quenching of the emitting B 3 П g state by molecular nitrogen. This view is supported by Jeunehomme & Duncan’s work on the pressure dependence of the lifetime of this state. Measurement of the absolute intensity of the afterglow when combined with their data show that about 50% of the recombination passes through the B 3 П g state. On this basis it is concluded that the A 3 Ʃ + u state and not the shallow 5 Ʃ + g state is the precursor of the afterglow. Levels of the B 3 П g state around v' = 12, 6 and 2 are populated by collision induced transition from the A state.

The kinetics of the recombination of oxygen atoms at a glass surface

1956 ◽  
Vol 234 (1199) ◽  
pp. 489-504 ◽  
Keyword(s):  
Oxygen Atom ◽  
Temperature Rise ◽  
Glass Surface ◽  
Concentration Distribution ◽  
Room Temperature ◽  
Atom Concentration ◽  
Electrodeless Discharge ◽  
First Order ◽  
Kinetics Of ◽  
Oxygen Atoms

Oxygen atoms were produced by electrode and electrodeless discharges in a stream of oxygen, and the concentration distribution in two side arms was studied with probes the tips of which catalyzed the recombination of oxygen atoms. Thermocouples recorded the resulting temperature rise which measures the oxygen atom concentration. The results show that the diffusion of oxygen atoms down the side arm is balanced by a wall removal process which is first order. The fractional collisional efficiency of this process is 1⋅2 + 10 -4 (± 50%) at room temperature and is independent of whether wet or dry oxygen is used. It increases only slightly with rise of temperature. The discharge between internal aluminium electrodes causes a change in the behaviour of the glass surface which may be due to the deposition of aluminium oxide. An electrodeless discharge is therefore to be preferred for the production of oxygen atoms and was used for most of these experiments.

Sign in / Sign up

Export Citation Format

Share Document