- On the high-resolution HeI photoelectron spectrum of Cl2O
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The high-resolution HeI (58.4 nm) photoelectron spectrum of dichlorine monoxide, Cl2O, has been recorded in the region of the four lowest-energy ionic electronic states. Formation of the ion in its ground and excited electronic states is accomp
- Motte-Tollet,Delwiche,Heinesch,Hubin-Franskin,Gingell,Jones,Mason,Marston
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- Absolute cross sections for the VUV optical absorption of Cl2O in the 6.5-9.7 eV energy range
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The VUV photoabsorption spectrum of dichlorine monoxide has been recorded between 6.5 and 9.7 eV photon energies using the UK Daresbury Synchrotron Radiation facility. The spectrum consists of a broad structureless band centred at 7.25 eV followed by several vibrationally resolved high-intensity bands. The 7.25 eV band has been interpreted in terms of the excitation of a dissociative valence excited state while the higher-energy electronic bands (above 7.5 eV) have been classified into several (n = 3, 4) Rydberg states linked with the ionic ground state and its lowest-energy excited states. An analysis of the vibrational progressions associated with the excitation of the various Rydberg states has been completed.
- Motte-Tollet,Ska,Marston,Walker,Siggel,Gingell,Kaminski,Brown,Mason
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- Kinetics of the ClO + NO2 + M Reaction
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The ClO + NO2 + M reaction has been studied with two techniques: Fourier transform infrared spectroscopy of the products, and flash photolysis-ultraviolet absorption to monitor the decay of ClO in excess NO2.The measured third-order rate constant is 1.5E-31 cm6 molecule-2 s-1 at 298 K with M=N2, in good agreement with previous literature values, but the rate constant appears to decrease by up to a factor of 3 in the presence of increasing amounts of OClO.For the infrared studies a stoichiometric mixture of ClO and NO2 was prepared in a flow system by mixing NO with OClO; at least as much NO2 as ClONO2 was produced under a variety of experimental conditions.These two sets of results are incompatible with the assumption made in previous kinetic studies that ClONO2 is the only recombination product; other isomers such as OClONO or ClOONO are likely to be formed three to four times faster.These results imply that potential stratospheric ozone depletion due to chlorofluoromethanes may be even larger than previously thought.
- Molina, Mario J.,Molina, Luisa T.,Ishiwata, Takashi
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- Rate Coefficient for the Termolecular Channel of the Self-Reaction of ClO
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The rate coefficient for the reaction ClO + ClO -> Cl2O2 has been measured by using a flash photolysis/UV absorption technique at temperatures from 200 to 263 K and pressures from 25 to 600 Torr in N2, O2, He, and SF6.Conventional single-wavelength detection and diode array spectrometry have both been employed in monitoring the reactant and product species.The UV absorption cross section of ClO has been measured in the same temperature range, from 220 to 350 nm, by using the diode array, and at 282.65 nm (the maximum of the ClO (9,0) band) by using the single-wavelength detection.The reactions of chlorine atoms with O3 and Cl2O have been used to produce ClO.The title reaction is believed to play a role in the loss of ozone from the Antarctic stratosphere during the austral spring.At the temperatures and pressures relevant to the Antarctic stratosphere, our measured values agree with the recent work of Sander et al. and are considerably smaller than the values obtained by Hayman et al.Over the range of conditions relevant to the Antarctic ozone loss, our measurements differ from Hayman et al. by a factor ranging from 1.3 to 3.0, with the discrepancy being ca. 1.9 at the altitude of maximum ozone loss.We have found Cl2O2 to be the major product of this reaction under these conditions, and we have established an upper limit of 1percent for the production of OClO.
- Trolier, M.,Mauldin, R. L.,Ravishankara, A. R.
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- Kinetic and Mechanistic Study of X + ClOCl -> Products (X = Br, Cl, F, O, OH, N) over the Temperature Range 240-373 K
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The rate constants for the reactions of X + ClOCl -> products for X = Br, Cl, F, O, OH, and N have been measured over the temperature range 230-400 K.The rate constants are (in units of cm3 molecule-1 s-1) as follows: (2.1 +/- 0.2) x 10-11 exp for Br + ClOCl; 6.0 +/- 0.6) x 10-11 exp for Cl + ClOCl; (1.5 +/- 0.5) x 10-10 exp for F + ClOCl; (1.3 +/- 0.8) x 10-11 exp for O + ClOCl; (1.7 +/- 0.8) x 10-12 exp for OH + ClOCl; and k298 -15 for N + ClOCl.The rate constants for X = Br, Cl, F, and N are found to correlate with the electron affinity of the attacking radical, suggesting that the mechanism for these reactions involves the partial transfer of an electron from ClOCl to X, and the activation energy for reaction is determined by the ability of the transition state to accommodate the shift in electron density.This trend is similar to that found for a number of non-hydrogen abstraction reactions (X + ClNO, O3, Cl2), where the reactivity scales with the quantity IP(molecule) - EA(radical), where IP refers to the ionization potential and EA the electron affinity.The reactions of O and OH with ClOCl are significantly faster than predicted by the trend, suggesting that the electron-transfer mechanism is not the only driving force in these reactions, which may involve long-range attractive forces leading to stable intermediates.
- Stevens, Philip S.,Anderson, James G.
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- CIO radical yields in the reaction of O(1D) with Cl2, HCl, chloromethanes, and chlorofluoromethanes
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Absolute CIO radical product yields in the gas-phase reactions of O( 1D) with Cl2, HCl, CCl4, CHCl3, CH 2Cl2, CH3Cl, CFCl3, CF 2Cl2, CF3Cl, CHFCl
- Feierabend, Karl J.,Papanastasiou, Dimitrios K.,Burkholder, James B.
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- The ultraviolet photodissociation of Cl2O at 235 nm and of HOCl at 235 and 266 nm
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The primary photochemistry of gas phase dichlorine monoxide (Cl2O) and of hypochlorous acid (HOCl) following excitation at 235 nm has been investigated using photofragment ion imaging to obtain the recoil velocity and angular distributions of the ground (2P3/2) and spin-orbit excited (2P1/2) atomic chlorine products. In the case of Cl2O, both Cl spin-orbit products exhibit angular distributions characterized by an anisotropy parameter, β=1.2±0.2, consistent with previous interpretations of the ultraviolet (UV) absorption spectrum of Cl2O which associate the broad intense absorption feature peaking at λ~255nm with excitation to a (bent) dissociative state of 1B2(C2v) symmetry. The recoil velocity distributions of the two Cl spin-orbit products are markedly different. The ground state atoms (which constitute >90% of the total Cl atom yield) are partnered by ClO fragments carrying significantly higher average levels of internal excitation. The slowest Cl atoms are most readily understood in terms of three body fragmentation of Cl2O to its constituent atoms. These findings are rationalized in terms of a model potential energy surface for the 11B2 state, which correlates diabatically with ClO(X) radicals together with a spin-orbit excited Cl atom, with efficient radiationless transfer to one (or more) lower energy surfaces at extended Cl-O bond lengths accounting for the dominance of ground state Cl atom fragments. The image of the ground state Cl atoms resulting from photolysis of HOCl at 235 nm is consistent with parent excitation via a transition for which the dipole moment is closely aligned with the Cl-O bond, followed by prompt dissociation (β=1.7±0.2) with the bulk of the excess energy partitioned into product recoil. Such conclusions are consistent with the results of laser induced fluorescence measurements of the OH(X) products resulting from 266 nm photodissociation of HOCl which reveal OH(X) products in both spin-orbit states, exclusively in their zero-point vibrational level, and carrying only modest levels of rotational excitation (well described by a Boltzmann distribution with Trot~750±50K).
- Tanaka, Yoshiki,Kawasaki, Masahiro,Matsumi, Yutaka,Fujiwara, Hisashi,Ishiwata, Takashi,Rogers, Leon J.,Dixon, Richard N.,Ashfold, Michael N. R.
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- Heterogeneous chemistry of Cl2O and HOCl on frozen natural sea salt, recrystallized sea salt, KCl and NaCl solutions at 200 and 215 K
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The HOCl heterogeneous reaction on frozen natural (NSS) and recrystallized (RSS) sea salt, KCl and NaCl solutions was studied using a low pressure flow reactor in order to measure the uptake coefficient γ and products of reaction. The HOCl sample used in these experiments always contained up to 25% Cl2O which was also studied separately as a pure gas in order to understand the heterogeneous chemistry of both gases. By performing HOCl uptake on frozen NSS solution at 200 K and a gas-phase residence time of (1.6±0.6) s we obtained a steady state uptake coefficient γHOCl on NSS = (2.5±0.7)×10-3 and ?Cl2O on NSS = (2.8±0.8)×10-3. On frozen KCl solution at 200 K we obtain ?HOCl on KCl = (2.8±1.3)×10-3, identical to NSS, and ?Cl2O on KCl = (4.6±0.8)×10-4. The main product formed during the uptake on frozen NSS solution is Cl2 which is sustained for at least one hour. In contrast, only a transient Cl2 flow (pulse) decreasing on the time scale of 100 s was observed on frozen KCl (NaCl) solution. 25±10 % of the HOCl taken up on all chloride-containing frozen substrates at 200 K react to produce Cl2 at high HOCl concentration (4.5×1011 molecule cm-3) and at a residence time of 1.6 s in comparison with twice that for Cl2O. For smaller concentrations such as [HOCl] = 3.7×1010 molecule cm-3 and.or a shorter residence time (0.137±0.004s), HOCl uptake did not generate Cl2 in contrast to Cl2O. A single Br2 burst event was monitored when a Cl2O or HOCl.Cl2O mixture is taken up on fresh frozen NSS solution during the first uptake at 200 K. Further Cl2O or HOCl.Cl2O uptake on the same sample, even after annealing at 240 K does not show an additional Br2 pulse. This Br2 release may be significant in the autocatalytic ozone destruction mechanism in the troposphere during polar sunrise. Some of the atmospheric implications of the present results are highlighted with emphasis on the preequilibrium Cl2O(ads) + H2O(ice)→←2 HOCl(ads) between adsorbed HOCl and Cl2O, with the latter being the gateway to reactive uptake of HOCl at low temperatures. by Oldenbourg Wissenschaftsverlag.
- Pratte, Pascal,Rossi, Michel J.
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- Dissociation pathways in low energy (0-2 eV) electron attachment to Cl2O
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Dissociative electron attachment (DA) to ClOCl is studied in a high resolution crossed beam experiment. Two complementary ion pairs, Cl-/ClO- and O-/Cl2-, are observed. The Cl-/ClO- pair arises from a simple Cl-OCl bond cleavage with the electron sitting on either of the two fragments. The O-/Cl2- pair is formed by a concerted reaction with the expulsion of O- (or O) and formation of Cl2 (or Cl2-). Ab initio calculations indicate that in low energy electron attachment an electronically excited state of the precursor anion (ClOCl-* (2B2)) is involved.
- Sailer, Wolfgang,Tegeder, Petra,Probst, Michael,Drexel, Herwig,Grill, Verena,Scheier, Paul,Mason, Nigel J.,Illenberger, Eugen,M?rk, Tilmann D.
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- UV absorption spectrum of the ClO dimer (Cl2O2) between 200 and 420 nm
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The UV photolysis of Cl2O2 (dichlorine peroxide) is a key step in the catalytic destruction of polar stratospheric ozone. In this study, the gas-phase UV absorption spectrum of Cl2O2 was measured using diode arr
- Papanastasiou, Dimitrios K.,Papadimitriou, Vassileios C.,Fahey, David W.,Burkholder, James B.
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p. 13711 - 13726
(2010/05/11)
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- MnO3Cl, isolation and crystal structure
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MnO3Cl is prepared from KMnO4 und ClSO3H. The thermally very unstable compound is identified by its Raman spectrum and a single crystal structure determination: a = 715.4(5), b = 1008.3(7), c = 500.9(4) pm, space group CmC
- Spandl, Johann,Supel, Joanna,Drews, Thomas,Seppelt, Konrad
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p. 2222 - 2225
(2008/10/09)
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- Kinetics of ClONO2 reactive uptake on ice surfaces at temperatures of the upper troposphere
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The reactive uptake kinetics of ClONO2 on pure and doped water-ice surfaces have been studied using a coated wall flow tube reactor coupled to an electron impact mass spectrometer. Experiments have been conducted on frozen film ice surfaces in the temperature range 208-228 K with P ClONO2 ≤ 10-6 Torr. The uptake coefficient (γy) of ClONO2 on pure ice was time dependent with a maximum value of γmax ~0.1. On HNO3-doped ice at 218 K the γmax was 0.02. HOCl formation was detected in both experiments. On HCl-doped ice, uptake was gas-phase diffusion limited (γ > 0.1) and gas-phase Cl2 was formed. The uptake of HCl on ice continuously doped with HNO3 was reversible such that there was no net uptake of HCl once the equilibrium surface coverage was established. The data were well described by a single site 2-species competitive Langmuir adsorption isotherm. The surface coverage of HCl on HNO3-doped ice was an order of magnitude lower than on bare ice for a given temperature and PHCl. ClONO2 uptake on this HCl/HNO3-doped ice was studied as a function of PHClHci. γmax was no longer gas-phase diffusion limited and was found to be linearly dependent on the surface concentration of HCl. Under conditions of low HCl surface concentration, hydrolysis of ClONO2 and reaction with HCl were competing such that both Cl2 and HOCl were formed. A numerical model was used to simulate the experimental results and to aid in the parametrization of ClONO2 reactivity on cirrus ice clouds in the upper troposphere.
- Fernandez, Miguel A.,Hynes, Robert G.,Cox, Richard A.
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p. 9986 - 9996
(2008/10/09)
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- Photodissociation dynamics of Cl2O: Interpretation of electronic transitions
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The photodissociation of Cl2O has been investigated for adjacent regions in the first and the second absorption bands, respectively, at dissociation wavelengths of 5.3 and 6.0 eV. Chlorine and oxygen atoms were state-selectively detected by resonance-enhanced multiphoton ionization. Chlorine fragment kinetic energy and spatial distributions were determined from time-of-flight profile analysis. At 5.3 eV, kinetic energy distributions are broad and bimodal and differ significantly for the two spin-orbit states Cl*(2P1/2) and Cl(2P3/2). The decay is characterized by a positive anisotropy parameter of 0.7 ± 0.2. Excitation proceeds via the transitions 10a1 ← 7b2 and 10a1 ← 9a1. The data are in agreement with generating ClO(X) + Cl*(2P1/2) as primary fragments. At 6.0 eV, kinetic energy distributions are narrow and structureless and are similar for the two spin-orbit states Cl*(2P1/2) and Cl(2P3/2). The decay is characterized by a small positive anisotropy parameter of 0.2 ± 0.2. The main dissociation channel is the three-body decay into 2C1 + O. The decay mechanism is of an asynchronous concerted type. The data suggest the primary production of ClO(A) + Cl( 2PJ). Excitation proceeds mainly via the transition 8b2 ← 7b2. The results show the need for refined theoretical calculations.
- Roth, Melanie,Maul, Christof,Gericke, Karl-Heinz
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p. 7954 - 7964
(2008/04/18)
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- Femtosecond pump-probe studies of dichlorine monoxide in solution
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The first femtosecond pump-probe studies of ClOCl photochemistry in solution are presented. Following 266-nm photoexcitation of ClOCl dissolved in perfluorohexane, the resulting evolution in optical density is monitored at seven wavelengths ranging from 266 to 400 nm. A depletion in optical density consistent with ground-state ClOCl photolysis is observed, followed by increases in optical density at 266 and 315 nm assigned to the production of ClO and ClClO, respectively. Kinetic analysis of the temporal evolution in optical density establishes that photoproduct appearance occurs on the ~10-ps time scale. Later time decay of the optical density at 315 nm is mirrored by a corresponding increase in optical density at 266 nm consistent with thermal decomposition of ClClO to produce ClO and Cl on the ~100-ps time scale. The quantum yields for photoproduct formation are determined through analysis of the absolute change in optical density. This analysis establishes that the quantum yields for ClClO and ClO production are 0.4 ±0.1 and 0.6 ± 0.1, respectively. Finally, the observation of ClClO production following ClOCl photoexcitation is similar to the behavior observed for chlorine dioxide (OClO) suggesting that photoisomerization is a general feature of halooxide reactivity in solution.
- Cooksey, Catherine C.,Reid, Philip J.
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p. 5508 - 5514
(2007/10/03)
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- The ultraviolet photodissociation of jet-cooled ClO and BrO radicals
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A molecular beam source for jet-cooled ClO and BrO radicals was developed using an electric discharge in order to study the UV photodissociation dynamics of these species. In the photodissociation of ClO, the wavelength dependence of the dynamics was observed. In the BrO experiments, the bond dissociation energy was directly measured.
- Zou, Peng,Kim, Hahkjoon,North, Simon W.
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p. 4176 - 4183
(2007/10/03)
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- Interaction of ozone with HCl sorbed on a thin layer of ice at 77 K
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A heterogeneous reaction of ozone with the ice-HCl(ads) system is studied over the temperature range 77-223 K. The process occurs extremely rapidly with the formation of a red condensate, which is supposedly (from the IR absorption spectroscopy data) composed of Cl2O and ClO2. At 77 K, the reaction supposedly proceeds according to the tunneling mechanism.
- Yagodovskaya,Savilov,Zosimov,Lunin
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p. 1028 - 1030
(2007/10/03)
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- Reflection-absorption IR spectroscopic investigation of the photolysis of thin films of dichlorine monoxide and chlorine dioxide
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Reflection-absorption infrared (RAIR) spectroscopy and mass spectrometry have been employed in order to investigate the low-temperature photochemistry of thin films of chlorine dioxide, OClO, and dichlorine monoxide, Cl2O, grown on a gold foil in an ultra-high vacuum system. Photolysis of a neat film of OClO (λ > 300 nm, 90-110 K) produces chloryl chloride, ClClO2. Irradiation of a co-deposited OClO/H2O film also produces chlorine superoxide, ClOO, which suggests that OClO isomerisation is the first step in the reaction producing ClClO2. Photolysis of Cl2O (300 2. Analysis of the observed IR band intensities and consideration of the metal surface selection (MSS) rule indicates that the photochemically produced OClO intermediate aligns perpendicular to the gold substrate. Mechanistic details and the atmospheric implications of the chemistry are discussed.
- Gane, Matt P.,Williams, Neil A.,Sodeau, John R.
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p. 2747 - 2753
(2007/10/03)
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- Heterogeneous kinetics of the uptake of ClONO2 on NaCl and KBr
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The uptake kinetics of ClONO2 on NaCl (reaction 1) and on KBr (reaction 2) have been studied in a low-pressure, Teflon-coated Knudsen reactor at room temperature. The initial uptake coefficient for both reactions has been measured as 0.23 ± 0.06 and 0.35 ± 0.06 for reactions 1 and 2, respectively, and is independent of reactant density in the range 1010-1013 molecules cm-3. The values of the uptake coefficients are independent of presentation of the salt substrates: identical results are obtained on powder, grains, single-crystal surfaces, and thin deposited salt layers. The only product of reaction 1 is Cl2. Reaction 2 initially produces Br2, followed by BrCl and Cl2. In our proposed mechanism, BrCl is the product of reaction 2, and secondary reactions between BrCl and the KBr substrate yield Br2 at short reaction times and Cl2 under prolonged exposure.
- Caloz, Francois,Fenter, Frederick F.,Rossi, Michel J.
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p. 7494 - 7501
(2007/10/03)
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- Rate Coefficients for the Thermal Decomposition of BrONO2 and the Heat of Formation of BrONO2
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Rate coefficients (k-7) for the thermal decomposition of bromine nitrate, BrONO2 + M -> BrO + NO2 + M, have been obtained at temperatures between 320 and 340 K and pressures between 100 and 1000 Torr.These data are combined with recommended values for the reverse reaction to obtain an equilibrium constant for the reaction pair, KP,7 = 5.44E-9 exp(14192/T) atm-1, and a heat of reaction for the thermal dissociation of 28.2 +/- 1.5 kcal/mol at 298 K.This reaction enthalpy is used in conjunction with literature data to arrive at a consistent set of ΔH0f(298 K) data for BrONO2 (10.1 +/- 2.0 kcal/mol), BrO (30.4 +/- 2.0 kcal/mol), HOBr (-14.1 +/- 2.0 kcal/mol), and Br2O (27.3 +/- 2.0 kcal/mol).Additional measurements were made to determine the rate coefficient for Br atom reaction with BrONO2 (k11) relative to the rate coefficient for its reaction with CH3CHO (k12) at 298 K: k11/k12 = 12.5 +/- 0.6.This relative rate measurement yields a rate coefficient of (4.9 +/- 1.5)E-11 cm3 molecule-1 s-1 for k11, using the currently recommended value for k12.Approximate rate constant for reaction of NO (reaction 17) and BrNO (reaction 19) with BrONO2 were also obtained: k17 = 3E-19 cm3 molecule-1 s-1, k19 > 1E-16 cm3 molecule-1 s-1.
- Orlando, John J.,Tyndall, Geoffrey S.
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p. 19398 - 19405
(2007/10/03)
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- Pressure-Dependent Yields and Product Branching Ratios in the Broadband Photolysis of Chlorine Nitrate
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The photolysis of chlorine nitrate was studied using broadband flash photolysis coupled with long-path ultraviolet-visible absorption spectroscopy.Branching ratios for the Cl + NO3 and ClO + NO2 product channels were determined from time-dependent measurements of ClO and NO3 concentrations.Yields of the ClO and NO3 products displayed a dependence on the bath gas density and the spectral distribution of the photolysis pulse.Product yields decreased with increasing bath gas density regardless of the spectral distribution of the photolysis pulse; however, the decrease in product yield was much more pronounced when photolysis was limited to longer wavelengths.For photolysis in a quartz cell (λ > 200 nm) the yield decreased by a factor of 2 over the pressure 10-100 Torr.In a Pyrex cell (λ > 300 nm), the yield decreased by a factor of 50 over the same pressure range.When photolysis was limited to λ > 350 nm, the yield decreased by a factor of 250.Branching ratios for the photolysis channels ClO + NO2 (1a) and ClONO2 + hν -> Cl + NO3 (1b) were determined from the relative ClO and NO3 product yields at various pressures.Although the absolute product yield displayed a pressure dependence, the branching between the two channels was independent of pressure.The relative branching ratios (assuming negligible contributions from other channels) are 0.61 +/- 0.20 for channel 1a and 0.39 +/- 0.20 for channel 1b for photolysis with λ > 200 nm and 0.44 +/- 0.08 for channel 1a and 0.56 +/- 0.08 for channel 1b for photolysis with λ > 300 nm.The implications of these results for the chemistry of the lower stratosphere are discussed.
- Nickolaisen, Scott L.,Sander, Stanley P.,Friedl, Randall R.
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p. 10165 - 10178
(2007/10/03)
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- Pressure dependence and metastable state formation in the photolysis of dichlorine monoxide (Cl2O)
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The photolysis of dichlorine monoxide (Cl2O) is investigated using broadband photolysis source with time-resolved absorption spectroscopy. Time-dependent concentrations of reactants and products are measured by long-path uv absorption spectrosc
- Nickolaisen,Miller,Sander,Hand,Williams,Francisco
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p. 2857 - 2868
(2008/10/09)
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- Eine gaskinetische Studie zur Reaktion von HOCl mit F-, Cl- und H-Atomen bei Raumtemperatur
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Chemical Kinetics / Elementary Reactions / Fluorescence / Mass Spectrometry / Radicals.The reactions of HOCl with F-, Cl- and H-atoms were investigated at room temperature in a discharge flow system equipped with an OH-resonance fluorescence cell and a mass spectrometric detector.All kinetic studies were carried out under pseudo first order conditions with HOCl being the minority component.Branching ratios for individual processes were obtained by following simultaneously the rates of HOCl consumption and product formation.The following rate constants (in units cm3 molecule-1 s-1) were determined: .Calibration for using reaction (1) for gas titration is discussed.The data are evaluated to yield ΔHf = -79.7 kJ mol-1 for the heat of HOCl formation.
- Vogt, R.,Schindler, R.N.
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p. 819 - 829
(2007/10/02)
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- Thermodynamic and kinetic properties of the reaction Cl + O2 + MClOO + M in the range 160-300 K and 1-1000 bar
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The reaction Cl + O2 + MClOO + M was studied by laser flash photolysis in the bath gases M = He, Ar, N2, and O2 over the temperature range 160-300 K and the pressure range 1-1000 bar.UV absorptions of ClOO were monitored, a maximum absorption cross section of ?(248 nm) = 3.4*10-17 cm2 was determined.An expression for the equilibrium constant Kp = 5.3*10-6 exp( + 23.4 kJ mol-1/RT) bar-1 was derived between 180 and 300 K, which, by a third law analysis, yields Η0 deg = -20.2 +/- 0.2 kJ mol-1.Limiting low pressure rate coefficients for Cl + O2 recombination of k0 = 8.8*10-34 (T/300 K)-3.0, k0 = 1.6*10-33 (T/300 K)-2.9, k0 = 1.4*10-33 (T/300 K)-3.9 cm6 s-1 were obtained over the range 160-260 K, as well as k0 (160 K) = 2.2*10-32 cm6 s-1.Rate constants for the reactions Cl + ClOO -> Cl2 + O2 or 2ClO, ClOO + ClOO -> products, and ClOO + Cl2 -> Cl2O + ClO were also derived.The recombination Cl + O2( + M) -> ClOO( + M) at pressures above 10 bar shows a transition to a high pressure plateau and, at pressures above 200 bar, to diffusion control.It is suggested that, like O + O2( + M) -> O3( + M), the reaction is governed by a radical complex mechanism.
- Baer, S.,Hippler, H.,Rahn, R.,Siefke, M.,Seitzinger, N.,Troe, J.
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p. 6463 - 6470
(2007/10/02)
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- Ultraviolet Absorption Cross Sections of Cl2O2 between 210 and 410 nm
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The ultraviolet and infrared absorption cross of Cl2O2 have been measured.The transient Cl2O2 molecule was produced by using the gas-phase reaction ClO + ClO + M -> Cl2O2 + M.Three independent ClO radical source reactions were used in this study: Cl + O3, Cl + Cl2O, and Cl + OClO.The Cl2O2 UV absorption spectrum was recorded over the range 200-450 nm with a diode array spectrometer over the temperature range 205-250 K.The Cl2O2 infrared absorption spectrum was recorded with a high-resolution Fourier transform spectrometer over the range 500-2000 1/cm.Both spectrometers were optically coupled to a fast flow multipass absorption cell.The UV absorption spectrum of Cl2O2 is a structureless continuum with a peak at 245 nm.The measurable absorption extends out to 410 nm.The UV absorption cross section at the peak of the spectrum, 245 nm, was measured to be (6.5+0.8-0.5) X 1E-18 cm2.Infrared absorption features centered at 560, 653, and 750 1/cm have been assigned to the Cl2O2 molecule.The present results are compared with other reported UV and IR measurements and the sources of discrepancies are discussed.The role of Cl2O2 in atmospheric chemistry and in particular the Antarctic ozone hole are discussed.
- Burkholder, James B.,Orlando, John J.,Howard, Carleton J.
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p. 687 - 695
(2007/10/02)
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- Reactions of chlorine fluorides and oxyfluorides with the nitrate anion and alkali-metal fluoride catalyzed decomposition of ClF5
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The binary chlorine fluorides ClF5, ClF3, and ClF, when used in an excess, all undergo facile fluorine-oxygen exchange reactions with the nitrate anion, forming FClO2, unstable FClO, and ClONO2, respectively, as the primary products. Whereas FClO3 does not react with LiNO3 at temperatures as high as 75°C, FClO2 readily reacts with either LiNO3 or N2O5 to give ClONO2 and O2 in high yield, probably via the formation of an unstable O2ClONO2 intermediate. With an excess of ClF, chlorine nitrate undergoes a slow reaction to give FNO2 and Cl2O as the primary products, followed by Cl2O reacting with ClF to give Cl2, ClF, and FClO2. The alkali-metal fluorides CsF, RbF, and KF catalyze the decomposition of ClF5 to ClF3 and F2, which can result in the generation of substantial F2 pressures at temperatures as low as 25°C.
- Christe, Karl O.,Wilson, William W.,Wilson, Richard D.
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p. 675 - 677
(2008/10/08)
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- Kinetics of the oxidation of calcium choride by oxygen activated in a glow discharge
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The study of the kinetics of the oxidation of calcium chloride by oxygen activated in a glow discharge has shown that the experimental data are described satisfactorily by the Erofeev-Kolmogorov topokinetic equation.Under these conditions, the nuclei of the solid calcium oxide phase grow preferentially in one direction.The IR spectra of the gaseous reaction products have been recorded.They indicate the formation of chlorine oxides of different composition.
- Morozova, N. P.,Dadashova, E. A.,Yagodovskaya, T. V.,Nekrasov, L. I.
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p. 1095 - 1096
(2007/10/02)
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- Novel process of producing phenyl or substituted phenylalkylamine pharmaceutical agents and novel chiral intermediates of high enantiomeric purity useful therein
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A process for producing the optically pure (+)- or (-) isomer of a phenyl- or substituted- phenylalkanolamine compounds having pharmacologic activity without the need for resoltuion processes ad novel intermediates useful in the process including optically pure haloalcohols are provided.
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- Decomposition of Calcium Chloride Under the Influence of a Glow Discharge in Oxygen
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The reaction of calcium chloride with the products of a glow discharge in oxygen at constant temperature and pressure have been studied.It is found that calcium chloride reacts with the active species present to give CaO, ClO2, and Cl2.The rate of the reaction is a maximum during the first two or three minutes, after which the reaction conditions become quasi-stationary; the degree of dechlorination of the initial product can reach 40percent.
- Yagodovskaya, T. V.,Dadasheva, E. A.,Nekrasov, L. I.
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p. 822 - 824
(2007/10/02)
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- Temperature Dependence of the Rate Constant and Product Channels for the BrO + ClO Reaction
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We have measured the rate constant for the reactions BrO + ClO -> Br + OClO (6a), BrO + ClO -> Br + Cl + O2 (6b), and BrO + ClO -> BrCl + O2 (6c) over the temperature range 241-408 K and found k6 = (8.2 +/- 1.0)E-12 cm3 molecule-1 s-1 independent of temperature.Measurement of the individual product branching ratios yielded values for channels 6a, 6b, and 6c equal to 0.55 +/- 0.10, 0.45 +/- 0.10, and a large fraction of the springtime ozon hole reported recently, provided that at least 20 ppt of total inorganic bromine is present, and it may provide a source of chlorine dioxide of sufficient magnitude to explain the recent measurements of this species in the Antarctic stratosphere.
- Hills, Alan J.,Cicerone, Ralph J.,Calvert, Jack G.,Birks, John W.
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p. 1853 - 1858
(2007/10/02)
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- ESR spectrum of ClO (2Π3/2) isolated in a CO2 matrix
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Upon isolation of ClO in a CO2 matrix at 10 K, a highly anisotropic ESR spectrum is observed which is attributed to ClO.This might be the first observation of a neutral radical with a 2Π ground state in a nonpolar matrix.Some of the structure discernible on the spectrum at 10 K may be related to ClO at different trapping sites.After annealing the sample at T > 45 K, the radical concentration diminishes and the g peak of the most prominent site splits into four peaks which may correspond to the hyperfine splitting of ClO.The spectrum can be explained by the following g and A tensors, gx = 1.889, gy = 1.899, gz = 2.66 and Ax = 111 MHz, Ay 20 MHz, Az 55 MHz.In a simple crystal field model these values are compared with molecular parameters of ClO deduced from gas phase spectra.
- Trainer, M.,Helten, M.,Knapska, D.
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p. 3648 - 3653
(2007/10/02)
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- Ester synthesis
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A novel process is described for the preparation of compounds of formula STR1 wherein R2 and R3 are each chloro or bromo; X is carboxyl, nitrile, optionally substituted carbonamide, carbonyl halide or an ester group. Those compounds wherein X is an appropriate ester group --COOB where B is an aryl group such as m-phenoxybenzyl are known insecticides; compounds where X is other than --COOB may be suitably converted thereto. The novel process consists of a series of steps from the corresponding acetyl compound of formula STR2 which comprises halogenation, reduction, esterification and finally elimination reactions.
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