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1.
Lifetimes have been measured for the Σ and Π vibronic Ã2A1 states of H2S+ by studying the decay curves of the Ã2A1 (0, υ′2, 0) → X? 2B1 (0, υ″2, 0) emission bands. The vibronic Ã2A1 states are produced via excitation of H2S molecules by 150 eV electrons. The Σ sublevels 1 ? υ′2 ? 7 and the Π sublevels 3 ? υ′2 ? 6 have been considered. Predissociation occurs in the Σ sublevels for υ′2 ? 7 and in the Π sublevels for υ′2 ? 6. The obtained radiative lifetimes for the non-predissociated Σ and Π sublevels are around 4.2(±0.4) × 10?6 s and 5.6(±0.5) × 10?6 s respectively. For the predissociated Σ(0, 7, 0) and Π(0, 6, 0) levels the corresponding lifetimes are 2.3(±0.3) × 10?6 s and 1.6(±0.3) × 10?6 s respectively. The rate constant for collisional deactivation (quenching) of the vibronic Ã2A1 states by H2S molecules was found to equal 2.3(±0.3) × 10?9 cm3 mol?1 s?1.  相似文献   

2.
The rate constant for the formation of H+5 (D+5) at (86 ± 3) °K by the three-body process has been determined (k3(H) = (2.16 ± 0.10) × 10?28 × 10?28 cm6/molecule2 sec and k3(D) = (1.47 ± 0.20) × 10?28 cm6/molecule2 sec) in a high pressure mass spectrometer. Comparison of this result with published rate data at 300 °K indicates the reaction has an apparent activation energy of ?1.5 kcal/mole.  相似文献   

3.
Absolute CD3 concentrations were measured in the flash photolysis of d6-HgMe2. An oscillator strength of (0.99 ± 0.10) × 10?2 was recorded for the 0O band of the B?—X? system, and a recombination rate coefficient of (4.9 ± 0.4) × 10?11 cm3 molecule?1 s?1 was derived. It is suggested that the probability of recombination per collision is virtually the same as for the CH3 radical.Some new bands of the B?—X? system have been discovered and tentatively assigned: from a study of the temperature dependence of the intensity of the 47300 cm?1 transition, Herzberg's scheme ‘b’ has been established for the vibrational assignment.  相似文献   

4.
CS radicals have been produced by photodissociation of CS2 at 193 nm and their disappearance monitored by LIF. The vibrationally excited CS radicals rapidly relax to CS(ν = 0). At 298 K, the rate coefficients for CS(ν = 0) reactions with O2, O3 and NO2 are (2.9 ± 0.4) × 10?19, (3.0 ± 0.4) × 10?16 and (7.6 ± 1.1) × 10?17 cm3 molecule?1 s?1 respectively. The quenching of CS(A 1II)ν=0 by He has a rate coefficient of (1.3 ± 0.2) × 10?12 cm3 molecule?1 s?1.  相似文献   

5.
The CL spectra of the title reactions and their pressure dependences have been studied over the 5 × 10?6 ? 5 × 10?3 torr range in a beam-gas experiment. In the Sm + N2O, O3 and Yb + O3 reactions simple bimolecular formation of the short lived (radiative lifetime τR < 3 × 10?6 s) MO* emitters dominates the entire pressure range. In the other systems Sm + (F2, Cl2), Yb + (F2, Cl2) the CL spectra are strongly pressure dependent, indicating extensive energy transfer from long-lived intermediates. Reaction mechanisms are suggested. The quantum yields Φ, obtained by calibrating relative quantum yields with Dickson and Zare's absolute value for Sm + N2O [Chem. Phys. 7 (1975) 367], range from Φ = 2.3% (for Sm + F2, the most efficient reaction) down to Φ = 0.005% for Yb + Cl2. The following lower limit estimates were obtained for the product dissociation energies from the short wavelength CL cutoffs: D00(SmF) ? 121.3 ± 2.4 kcal/mole, D00(SmCl) ? ? 100 ± 3 kcal/mole, D00(YbO) ? 94.2 ± 1.5 kcal/moie, D00(YbF) ? 123.7 ± 2.3 kcal/mole.  相似文献   

6.
The time-resolved laser magnetic resonance (LMR) method has been applied to kinetic measurements for the first time. An intracavity spectrometer based on a CO2 laser with resonant modulation of the magnetic field and with phase-sensitive detection of the signal has been used. Kinetic curves of generation and disappearance of CI atoms and SiH3 radicals were obtained in the pulse photolysis of a mixture of S2Cl2 + SiH4 under the fourth harmonic of a Nd laser (265 nm, 0.5 mJ, 12.5 Hz) at a total pressure of 520–980 Pa (he as diluent) and a temperature of 326 K. The reagent concentrations were: [S2Cl2 = (2.0?10.2)×1014 cm?3, [SiH4 = (2.4?17.4)×1013 cm?3. To remove the transition saturation, 5.3×1015 cm?3 CCl4 was introduced into the reactor. The fraction of dissociated S2Cl2 was 1‰ Rate constants of the reactions (I) Cl+S2Cl2 → products, (II) Cl+SiH4 → HCl+SiH3 and a preliminary rate constant of the reaction (III) SiH3 + S2Cl2 → products were obtained: k1 ≤ (4.3±1.2)×10?12 cm3/s, k2 = (2.3±0.5)×10?10 cm3/s, k3 = (2.4±0.5)×10?11 cm3/s. At a signal-to-noise ratio of 1:1, 1000 pulses and a 12 cm long detection zone the sensitivity to Cl atoms and to SiH3 radicals was 4×1010 cm?3 and = 1011 cm?3, respectively. The time resolution of the method was 4 μs. The method is shown to be promising for kinetic investigations and experiments on fast processes.  相似文献   

7.
A combined EPR/LMR spectrometer and fast-flow system has been used to investigate the reactions HO2 + NO(k1), HO2 + OH(k2), HO2 + HO2(k3) at room temperature. The rate constants have been measured: k1 = (7.0 ± 0.6) × 10?12 cm3 s?1 (P = 7–10 Torr);k2 = (5.2 ± 1.2) × 10?11 cm3 s?1 (P = 8–10 Torr);k3 = (1.65 ± 0.3) × 10?12 cm3 s?1 (P = 2.1–24.9 Torr). The conclusion is drawn from analysis of the literature and the present work that k2 and k3 do not depend on pressure up to 1 atm.  相似文献   

8.
Dissociative electron attachment cross-section measurements for the production of O? from CO2 have been performed utilizing a crossed target-beam—electron-beam collision geometry and a quadrupole mass spectrometer. The relative flow technique is employed to determine the absolute values of cross sections. The attachment energies corresponding to the five cross-section maxima are: 4.4 ± 0.1, 8.2 ± 0.1, 13.0 ± 0.2, 16.9 ± 0.2 and 19.4 ± 0.2 eV. The cross sections at these maxima are: 1.43 × 10?19 cm2, 4.48 × 10?19 cm2, 8.1 × 10?21 cm2, 8.1 × 10?21 cm2 and 1.2 × 10?20 cm2, respectively.  相似文献   

9.
The rate coefficient for the reaction of CF3O2 with NO has been measured at 295 K in helium using a flow tube sampled by a mass spectrometer. The value obtained for this rate coefficient was (17.8 ± 3.6) × 10?12 cm?3 s?1 and found to be independent of [He] over the range (6.3 ? 16.8) × 1016 cm?3. This value is approximately a factor of 2 higher than earlier measurements of the rate coefficients for CH3O2 and C2H5O2 with NO and indicates that further measurements are required for this important class of reactions.  相似文献   

10.
The decay of NH2 radicals, from 193 nm photolysis of NH3, was monitored by 597.7 nm laser-induced fluorescence. Room-temperature rate constants of (1.21 ± 0.14) × 10?10, (1.81 ± 0.12) × 10?11, and (2.11 ± 0.18) × 10?11 cm3 molecule?1 s?1 were obtained for the reactions of NH2 with N, NO and NO2, respectively. The production of NH in the reaction of NH2 with N was observed by laser-induced fluorescence at 336.1 nm.  相似文献   

11.
Rate coefficients for the collisional quenching of O2*(1Δg) by NO and CO2 at 2–8 torr and 300 K have been determined. kNO = (2.48 ± 0.23) × 10?17 cm3 molecule?1 s?1 and
= (2.56 ± 0.12) × 10?18 cm3 molecule?1 s?1.  相似文献   

12.
The photodissociation of ketene, CH2CO(X?1A1) → CH21A1) + CO(X 1Σ+) has been observed at 337 nm, using a pulsed nitrogen laser. The CH21A1) radical has been detected by laser induced fluorescence with a tunable dye laser. A laser excitation spectrum has been obtained from CH21A1) over the wavelength interval from 588.9 to 595.6 nm in the Σ ← Π vibronic subband of the CH21A1); υ″ = 0, 0, 0?b? 1B1; υ′ = 0, 14, 0) transition. For the CH21A1 ; υ′= 0, 0, 0?X? 3B1; υ′' = 0, 0, 0) energy separation an upper limit of (6.3 ± 0.8) kcal/mole has been found. The radiative lifetime τ and the rate constant k for the removal of the 000 rotational level of the Σ(0, 14, 0) vibronic state have been measured directly. The values are τ = (4.2 ± 0.2) μs and k = (7.4 ± 0.3) × 10?10 cm3 molecule?1 s?1, respectively.  相似文献   

13.
The absolute rate constant of the reaction of NH2 with NO2 has been measured using a flash-photolysis laser resonance-fluorescence technique. The value obtained at room temperature is k1 = 2.3 (± 0.2) × 10?11 cm3 molecule ?1 s?1. A negative temperature coefficient has been found between 298 and 505 K for this reaction, k1 = 3.8 × 10?8 × T?1.30 cm3 molecule?1 s?1. It is thought that this is the major reaction of NH2 in the troposphere.  相似文献   

14.
A value of (9.3 ± 1.7) × 10?15 cm3 molecule ?1 has been determined as the rate constant for the quenching of O2(A 3Σu+) by N2 at 25°C.  相似文献   

15.
Rate constants for the reaction of O(3P) atoms with C3H4, C3H6 and NO(M = N2O) have been measured over the temperature range 300–392°K using a modulation-phase shift technique. The Arrhenius expressions obtained are:C2H4, k2 = 3.37 × 109 exp[?(1270 ± 200)/RT]liter mole?1 sec?1,C3H6, k2 = 2.08 × 109 exp[?(0 ± 300)/RT]liter mole?1 sec?1,NO(M = N2O), k1 = 9.6 × 109 exp[(900 ± 200/RT]liter2 mole?2 sec?1.These temperature dependencies of k2 are in good agreement with recent flash photolysis-resonance flourescence measurements, although lower than previous literature values.  相似文献   

16.
NH(A3Π → X3Σ?) and OH(A2Σ+ → X2Π) chemiluminescences from the reaction of CH(X2Π) with NO and O2, respectively, have been observed at room temperature. From the decay of such emissions we have measured the rate constants for these two reactions: kNO = (2.5 ± 0.5) × 10?10 and kO2 = (8 ± 3) × 10?11 cm3 molecule ?1 s?1, which are in agreement with previously reported rates determined by direct CH(X) detection using, laser-induced fluorescence. This indicates that a four-centered mechanism generating these excited species is operative in both reactions. The CH generation from 266 nm photolysis of CHBr3 has also been investigated via analysis of CH* emissions.  相似文献   

17.
The rate constants for the reactions C2O + H → products (1) and C2O + H2 → products (2) have been determined at room temperature by means of laser-induced fluorescence detection of C2O radicals, generated either by the KrF excimer laser photolysis Of C3O2, or by the reaction of C3O2 with O atoms. Values of k1 = (3.7 ± 1.0) × 10?11 cm3 s?1 and k2 = (7 ± 3) × 10?13 cm3 s?1 were obtained.  相似文献   

18.
The electrochemical reduction of SO2 in dimethylformamide at Pt electrodes finally leads to the red species S3O2?6 via the blue complex S2O·?4. The UV-VIS absorption coefficients are determined: ?(S2O·?4) = (224 ± 25) × 105 cm2 mol?1; ?(S3O2?6) = (0.64 + 0.07) × 105 cm2 mol?1. A calculation of the complexing constant of SO2 with free SO·?2 radical based on potential shifts confirms this constant to be in the range of 200–700 1 mol?1.Two potentiometric titration methods (viz: with allylbromide and tetraethylammoniumtribromide) for analysis of electrolytically generated SIII-oxo-anions in DMF are presented. Reactions of those anions with aromatic aldehydes and trials for trapping of possibly formed SO are described.  相似文献   

19.
The rate constant for collisional deactivation of CO2(0001) in pure CO2 has been measured at room temperature using the laser fluorescence technique. The relaxation rate has been found to be (1.0 ± 0.2) × 10?14 cm3 s?1 which is in favorable agreement with previously published values.  相似文献   

20.
Using the delayed coincidence technique, lifetimes have been measured for some Σ and Π vibronic Ã2A1 states of H2O+ and for the 3Πi (υ′ = 0) state of OH+ by analysing the decay curves of the Ã2A1(0, υ′2, 0) ? X?2B1 (0, υ″2, 0) and the 3Πi(υ′ = 0) ? 3Σ?(υ″ = 0) emission intensities respectively. The excited molecular ionic states are produced via excitation of H2O molecules by 200 eV electrons. For H2O+2A1) the vibronic Σ levels with υ′2 = 13 and 15 and the vibronic Π levels with υ′2 = 12 and 14 have been considered. The radiative lifetimes obtained for these levels have about the same value, namely 10.5(±1) × 10?6 s. The radiative lifetime for the OH+(3Πiυ′= 0) state is 2.5(±0.3) × 10?6 s. The lifetimes found in this work for H2O+2A1) and OH+(3Πi,υ′= 0) are about ten and three times longer respectively than the corresponding lifetimes given by other investigators [1,2]. The probable reason for this discrepancy is that in the other experiments no attention has been paid to the presence of a large space charge effect. This effect is caused by the positive ions which are created by the primary electron beam.  相似文献   

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