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Butkovskaya NI Kukui A Pouvesle N Le Bras G 《The journal of physical chemistry. A》2005,109(29):6509-6520
A high-pressure turbulent flow reactor coupled with a chemical ionization mass spectrometer was used to investigate the minor channel (1b) producing nitric acid, HNO3, in the HO2 + NO reaction for which only one channel (1a) is known so far: HO2 + NO --> OH + NO2 (1a), HO2 + NO --> HNO3 (1b). The reaction has been investigated in the temperature range 223-298 K at a pressure of 200 Torr of N2 carrier gas. The influence of water vapor has been studied at 298 K. The branching ratio, k1b/k1a, was found to increase from (0.18(+0.04/-0.06))% at 298 K to (0.87(+0.05/-0.08))% at 223 K, corresponding to k1b = (1.6 +/- 0.5) x 10(-14) and (10.4 +/- 1.7) x 10(-14) cm3 molecule(-1) s(-1), respectively at 298 and 223 K. The data could be fitted by the Arrhenius expression k1b = 6.4 x 10(-17) exp((1644 +/- 76)/T) cm3 molecule(-1) s(-1) at T = 223-298 K. The yield of HNO3 was found to increase in the presence of water vapor (by 90% at about 3 Torr of H2O). Implications of the obtained results for atmospheric radicals chemistry and chemical amplifiers used to measure peroxy radicals are discussed. The results show in particular that reaction 1b can be a significant loss process for the HO(x) (OH, HO2) radicals in the upper troposphere. 相似文献
2.
Motret O. Pellerin S. Nikravech M. Massereau V. Pouvesle J. M. 《Plasma Chemistry and Plasma Processing》1997,17(4):393-407
Plasma processing of a (CH
4
+CO
2
) mixture can lead to the formation of synthesis gas (CO+H
2
). The use of a nonthermal plasma for this type of process seems very promising. We report here an electric and spectroscopic characteristic of plasma created in a (CH
4
+CO
2
) mixture by a high-voltage, steep front-voltage (>10
12
V/s), very-short-pulse triggered dielectric barrier discharge in a tubular cell. Particular attention was payed to the determination of the rotational temperature for C
2
. Time resolved investigation of the Swan band leads to an estimated value around 3000 K. 相似文献
3.
Pouvesle N Kippenberger M Schuster G Crowley JN 《Physical chemistry chemical physics : PCCP》2010,12(47):15544-15550
The interaction of H(2)O(2) with ice surfaces at temperatures between 203 and 233 K was investigated using a low pressure, coated-wall flow tube equipped with a chemical ionisation/electron impact mass spectrometer. Equilibrium surface coverages of H(2)O(2) on ice were measured at various concentrations and temperatures to derive Langmuir-type adsorption isotherms. H(2)O(2) was found to be strongly partitioned to the ice surface at low temperatures, with a partition coefficient, K(linC), equal to 2.1 × 10(-5) exp(3800/T) cm. At 228 K, this expression results in values of K(linC) which are orders of magnitude larger than the single previous determination and suggests that H(2)O(2) may be significantly partitioned to the ice phase in cirrus clouds. The partition coefficient for H(2)O(2) was compared to several other trace gases which hydrogen-bond to ice surfaces and a good correlation with the free energy of condensation found. For this class of trace gas a simple parameterisation for calculating K(linC)(T) from thermodynamic properties was established. 相似文献
4.
Butkovskaya NI Pouvesle N Kukui A Mu Y Le Bras G 《The journal of physical chemistry. A》2006,110(21):6833-6843
The mechanism of the gas-phase reaction of OH radicals with hydroxyacetone (CH3C(O)CH2OH) was studied at 200 Torr over the temperature range 236-298 K in a turbulent flow reactor coupled to a chemical ionization mass-spectrometer. The product yields and kinetics were measured in the presence of O2 to simulate the atmospheric conditions. The major stable product at all temperatures is methylglyoxal. However, its yield decreases from 82% at 298 K to 49% at 236 K. Conversely, the yields of formic and acetic acids increase from about 8% to about 20%. Other observed products were formaldehyde, CO2 and peroxy radicals HO2 and CH3C(O)O2. A partial re-formation of OH radicals (by approximately 10% at 298 K) was found in the OH + hydroxyacetone + O2 chemical system along with a noticeable inverse secondary kinetic isotope effect (k(OH)/k(OD) = 0.78 +/- 0.10 at 298 K). The observed product yields are explained by the increasing role of the complex formed between the primary radical CH3C(O)CHOH and O2 at low temperature. The rate constant of the reaction CH3C(O)CHOH + O2 --> CH3C(O)CHO + HO2 at 298 K, (3.0 +/- 0.6) x 10(-12) cm3 molecule(-1) s(-1), was estimated by computer simulation of the concentration-time profiles of the CH3C(O)CHO product. The detailed mechanism of the OH-initiated oxidation of hydroxyacetone can help to better describe the atmospheric oxidation of isoprene, in particular, in the upper troposphere. 相似文献
5.
C. B. Collins A. C. Rusu N. C. Zoita M. C. Iosif D. T. Camase F. Davanloo C. A. Ur I. I. Popescu J. M. Pouvesle R. Dussart V. I. Kirischuk N. V. Strilchuk F. J. Agee 《Hyperfine Interactions》2001,135(1-4):51-70
Because of the high density of energy storage and the large cross section for its release, nuclear spin isomers have attracted
considerable recent interest. The triggering of induced gamma emission from them has encouraged efforts to develop intense
sources of short-wavelength radiation. One of the more interesting examples is the 16+ 4-qp isomer of 178Hf which stores 2.445 MeV for a half-life of 31 years meaning that as a material, such isomeric 178Hf would store 1.3 GJ/g. Recently, a sample containing 6.3×1014 nuclei of the isomer of 178Hf was irradiated with X-ray pulses derived from a device operated at 15 mA to produce bremsstrahlung radiation with end point
energies set to values between 60 and 90 keV. Emission of gamma radiation from the sample was increased by 1–2% above the
quiescent value of spontaneous emission. Such an accelerated decay of the 178Hf isomer is consistent with an integrated cross section of 2.2×10−22 cm2 keV if the resonant absorption of the X-rays takes place below 20 keV as indicated by the use of selective absorbing filters
in the irradiating beam. The work reported here describes the current experimental focus and results recently obtained with
the use of coincident detection of emitted gamma photons by several detectors.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
von Hessberg P Pouvesle N Winkler AK Schuster G Crowley JN 《Physical chemistry chemical physics : PCCP》2008,10(17):2345-2355
The physical adsorption of formic (HC(O)OH) and acetic (CH(3)C(O)OH) acid on ice was measured as a function of concentration and temperature. At low concentrations, the gas-ice interaction could be analysed by applying Langmuir adsorption isotherms to determine temperature dependent partition constants, K(Lang). Using temperature independent saturation coverages (N(max)) of (2.2 +/- 0.5) x 10(14) molecule cm(-2) and (2.4 +/- 0.6) x 10(14) molecule cm(-2) for HC(O)OH and CH(3)C(O)OH, respectively, we derive K(Lang)(HC(O)OH) = 1.54 x 10(-24) exp (6150/T) and K(Lang)(CH(3)C(O)OH) = 6.55 x 10(-25) exp (6610/T) cm(3) molecule(-1). Via a van't Hoff analysis, adsorption enthalpies were obtained for HC(O)OH and CH(3)C(O)OH. Experiments in which both acids or HC(O)OH and methanol interacted with the ice surface simultaneously were adequately described by competitive adsorption kinetics. The results are compared to previous measurements and used to calculate the equilibrium partitioning of these trace gases to ice surfaces under conditions relevant to the atmosphere. 相似文献
7.
C. B. Collins F. Davanloo M. C. Iosif R. Dussart J. M. Hicks S. A. Karamian C. A. Ur I. I. Popescu V. I. Kirischuk J. M. Pouvesle P. McDaniel C. E. Crist 《Physics of Atomic Nuclei》2000,63(12):2067-2072
A sample containing 6.3×1014 nuclei of the 16+ isomer of 178Hf having a half-life of 31 yr and an excitation energy of 2.446 MeV was irradiated with x-ray pulses from a device operated at 15 mA to produce bremsstrahlung with an endpoint energy of 90 keV. The gamma spectra of the isomeric target were taken with a Ge detector. The intensity of the 325.5-keV (6+ → 4+) transition in the ground-state band of 178Hf was found to increase by about 2%. Such an enhanced decay of the 178Hf isomer is consistent with an integrated cross section value of 3×10?23 cm2 keV if resonance absorption occurs within energy ranges corresponding to the maxima of the x-ray flux, either near 20 keV or at the energies of the characteristic emission lines of W. 相似文献
8.
Butkovskaya NI Pouvesle N Kukui A Bras GL 《The journal of physical chemistry. A》2006,110(50):13492-13499
The mechanism of the gas-phase OH-initiated oxidation of glycolaldehyde (HOCH(2)CHO) was studied in the 233-296 K temperature range using a turbulent flow reactor coupled with a chemical ionization mass spectrometer. In the presence of O2, formaldehyde, CO2, formic acid, and glyoxal were observed at room temperature with the yields of 80, 34, 18, and 14%, respectively. Decrease of temperature to 233 K led to significant changes in the yields of the stable products: those of formaldehyde and glyoxal decreased to 50 and 4%, respectively, whereas that of formic acid increased to 52%. It was also found that the OH + glycolaldehyde + O2 reaction proceeds with considerable reformation of OH radicals (by 25% at 296 K). The observed product yields are explained by a mechanism including formation of short-lived intermediate adducts of the primary radicals with O2. The implication of the obtained results for the HOx budget in the upper troposphere is discussed. 相似文献
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