Gas Kinetic Rate Research Articles

Reaction N(2D) + CH2CCH2 (Allene): An Experimental and Theoretical Investigation and Implications for the Photochemical Models of Titan.

We report on a combined experimental and theoretical investigation of the N(2D) + CH2CCH2 (allene) reaction of relevance in the atmospheric chemistry of Titan. Experimentally, the reaction was investigated (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy (Ec) of 33 kJ/mol to determine the primary products and the reaction micromechanism and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 to 296 K. Theoretically, electronic structure calculations of the doublet C3H4N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed via barrierless addition of N(2D) to one of the two equivalent carbon–carbon double bonds of CH2CCH2, followed by the formation of several cyclic and linear isomeric C3H4N intermediates that can undergo unimolecular decomposition to bimolecular products with elimination of H, CH3, HCN, HNC, and CN. The kinetic experiments confirm the barrierless nature of the reaction through the measurement of rate constants close to the gas-kinetic rate at all temperatures. Statistical estimates of product branching fractions (BFs) on the theoretical PES were carried out under the conditions of the CMB experiments at room temperature and at temperatures (94 and 175 K) relevant for Titan. Up to 14 competing product channels were statistically predicted with the main ones at Ec = 33 kJ/mol being formation of cyclic-CH2C(N)CH + H (BF = 87.0%) followed by CHCCHNH + H (BF = 10.5%) and CH2CCNH + H (BF = 1.4%) the other 11 possible channels being negligible (BFs ranging from 0 to 0.5%). BFs under the other conditions are essentially unchanged. Experimental dynamical information could only be obtained on the overall H-displacement channel, while other possible channels could not be confirmed within the sensitivity of the method. This is also in line with theoretical predictions as the other possible channels are predicted to be negligible, including the HCN/HNC + C2H3 (vinyl) channels (overall BF < 1%). The dynamics and product distributions are dramatically different with respect to those observed in the isomeric reaction N(2D) + CH3CCH (propyne), where at a similar Ec the main product channels are CH2NH (methanimine) + C2H (BF = 41%), c-C(N)CH + CH3 (BF = 32%), and CH2CHCN (vinyl cyanide) + H (BF = 12%). Rate coefficients (the recommended value is 1.7 (±0.2) × 10–10 cm3 s–1 over the 50–300 K range) and BFs have been used in a photochemical model of Titan’s atmosphere to simulate the effect of the title reaction on the species abundance (including any new products formed) as a function of the altitude.

Rate coefficients for the CH(X2Π) + CHX3 (X = Cl and Br) reactions and the propensity of the reactions of CH with halomethanes

Methylidyne (CH) was generated in the ultraviolet multiphoton photolysis of CHCl3 and CHBr3 and detected with laser-induced fluorescence (LIF) via the A2Δ − X2Π (0,0) transition. The time-resolved LIF intensity recorded at varying pressures of CHCl3 and CHBr3 has given the overall rate coefficients for the reactions of CH with CHCl3 and CHBr3. The near gas kinetic rates indicate that CH inserts into the C − Cl and C − Br bonds. The correlation between the rate coefficients for the CH + CHnX4−n (X = F, Cl, and Br) reactions and the heats of reactions for H-, Cl-, Br-elimination is elucidated by the Evans − Polanyi principle.

Identification of molecular cluster evaporation rates, cluster formation enthalpies and entropies by Monte Carlo method

Abstract. We address the problem of identifying the evaporation rates for neutral molecular clusters from synthetic (computer-simulated) cluster concentrations. We applied Bayesian parameter estimation using a Markov chain Monte Carlo (MCMC) algorithm to determine cluster evaporation/fragmentation rates from synthetic cluster distributions generated by the Atmospheric Cluster Dynamics Code (ACDC) and based on gas kinetic collision rate coefficients and evaporation rates obtained using quantum chemical calculations and detailed balances. The studied system consisted of electrically neutral sulfuric acid and ammonia clusters with up to five of each type of molecules. We then treated the concentrations generated by ACDC as synthetic experimental data. With the assumption that the collision rates are known, we tested two approaches for estimating the evaporation rates from these data. First, we studied a scenario where time-dependent cluster distributions are measured at a single temperature before the system reaches a steady state. In the second scenario, only steady-state cluster distributions are measured but at several temperatures. Additionally, in the latter case, the evaporation rates were represented in terms of cluster formation enthalpies and entropies. This reparameterization reduced the number of unknown parameters, since several evaporation rates depend on the same cluster formation enthalpy and entropy values. We also estimated the evaporation rates using previously published synthetic steady-state cluster concentration data at one temperature and compared our two cases to this setting. Both the time-dependent and the two-temperature steady-state concentration data allowed us to estimate the evaporation rates with less variance than in the steady-state single-temperature case. We show that temperature-dependent steady-state data outperform single-temperature time-dependent data for parameter estimation, even if only two temperatures are used. We can thus conclude that for experimentally determining evaporation rates, cluster distribution measurements at several temperatures are recommended over time-dependent measurements at one temperature.

Effect of liquid carbon dioxide on coal pyrolysis and gasification behavior at subcritical pressure conditions

Pyrolysis involving gaseous carbon dioxide has been analyzed previously; however, pyrolysis behaviors of coal–liquid carbon dioxide (LCO2) slurries have not been examined yet. In this study, the effect of wet LCO2–coal feeding on pyrolysis and gasification behavior was examined and compared with that of dry coal feeding. The first wet feeding method comprised simultaneous mixing and supply of coal with LCO2. However, the second feeding supplied coal via liquid or gaseous CO2 introduction, which could simulate conventional dry feeding for coal transport applications. The product gas yield and kinetic rate were determined from pyrolysis experiments at two subcritical pressure conditions of CO2. The wet LCO2–coal feeding produced more CO gas yield than that of dry coal feeding, which is observed at low-pressure condition. The result for high-pressure condition further supports better pyrolysis behavior of wet feeding. This may be attributed to easy CO2 diffusion or change in coal structure resulting from LCO2 flash/evaporation process. The highest conversion of coal to product gases was observed with water–coal slurry, particularly for the high-pressure fixed-bed condition.

Modeling of a Microwave Plasma Driven Biomass Pyrolitic Conversion for Energy Production

The thermal decomposition of biomass particles in a microwave plasma operating at atmospheric pressure conditions has been theoretically investigated. The set of equations, including thermal balance equations for the gas and biomass particles and kinetic rate balance equations for stable and intermediate components of biomass decomposition was solved for two different assumptions: thermal equilibrium and non‐equilibrium. The thermal equilibrium assumption is acceptable given the high temperature and high reaction rates achievable in the microwave plasma environment, and although it hides the evolution of the pyrolysis process, it allows the description of the detailed chemical composition of the stable pyrolysis by‐products (H2, CO, C2H2, and C [solid]).

Pengaruh Temperatur Terhadap Entalpi dan Kinetic Rate Gas Pirolisis Kayu Mahoni

This study was conducted to determine the effect of temperature on gas enthalpy and kinetic rate of mahogany wood powder pyrolysis results. Research process carried out experimentally with the temperature 673 K, 773 K, 873K, 973 K and 1073 K. Pyrolysis process is carried out for 2 hours with a particle size of sawdust from 0.5 to 1 mm. The results showed that the enthalpy value increase as the temperature increase. Highest enthalpy value achieved at 1073 K, with enthalpy value is 35015.97J.Kinetic rate for temperature 873 K, 973 K and 1073 K is 𝑘 = 1,484𝑒 −2759/𝑇 , kinetic rate for temperature 673 K and 773 K is 𝑘 = 16,5306𝑒 −5368/𝑇 and 𝑘 = 3,0373𝑒 −2980/𝑇 respectively. As the temperature increase, activation energy (Ea) to decompose biomass into gases is decrease.

Why mixtures of hydrazine and dinitrogen tetroxide are hypergolic?

The reactions of N2H4 with N2O4 isomers have been investigated at the G2M(CC3)//B3LYP/6-311++G(3df,2p) level. The results show that the reactions of N2H4 with sym-N2O4 (D2h), cis-ONONO2 (Cs), and NO2 have to overcome 14.2, 10.6, and 7.6kcal/mol barriers, respectively. However, N2H4 can react spontaneously with trans-ONONO2 (Cs) and cis-ONONO2 (C1) to produce HONO2+H2NN(H)NO with the near gas-kinetic rate constant, 4×10−10cm3molecule−1s−1 above 250K. The H2NN(H)NO thus formed can rapidly fragment to give reactive N2H3 radical with rate constant >1×107s−1 at 1000K, which is fast enough to initiate the hypergolic chain reactions with NO2 and N2O4.

Kinetics of elementary steps in the reaction of atomic bromine with 2,3‐dimethyl‐2‐butene under atmospheric conditions

AbstractWe have employed the laser flash photolysis–resonance fluorescence technique to investigate the gas‐phase kinetics of elementary steps in the Br‐initiated oxidation of 2,3‐dimethyl‐2‐butene (TME) under atmospheric conditions. At T⩾ 274 K, measured rate coefficients are independent of pressure suggesting hydrogen abstraction as the dominant pathway. The following Arrhenius expression adequately describes all kinetic data at 274 K ⩽T⩽ 420 K: k1a(T) = (3.84 ± 0.84) × 10− 11 exp[(−169 ± 61)/T] cm3 molecule−1s−1 (uncertainties are 2σ, precision only). At 203 K ⩽T⩽ 241 K, kinetic evidence for reversible addition, Br + TME ↔ Br−TME (k1b, k−1b), is observed. Analysis of the approach to equilibrium data allows evaluation of the rate coefficients k1b and k−1b. At atmospheric pressure addition of Br to TME occurs at a near gas kinetic rate. Equilibrium constants are obtained from k1b/k−1b. Combining the experimental results with electronic structure calculations allows third‐law analyses of the equilibrium data. The following thermochemical parameters for the addition reaction (1b) at 0 and 298 K are obtained (standard state = 1 atm): ΔrH0= −47.1 ± 3.0 kJ mol−1, ΔrH298=−47.3 ± 3.0 kJ mol−1, and ΔrS298=−101.5 ± 10.0 J mol−1 K−1. Examination of the effect of added O2 on Br atom kinetics under conditions where reversible adduct formation is observed allows determination of the rate coefficient for the Br–TME + O2 reaction (k2). At 223 K, we find that k2 increases from 3.9 to 5.5 × 10−12 cm3 molecule−1s−1 as pressure increases from 25 to 200 Torr. Our results suggest that under most atmospheric conditions the Br–TME reaction with O2 occurs more rapidly than the Br–TME unimolecular decomposition. Hence, the fast addition reaction appears to control the rate of TME loss by reaction with Br in the atmosphere. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 44: 13–26, 2012

Selected ion flow tube, SIFT, studies of the reactions of H 3O +, NO + and O 2+ with some biologically active isobaric compounds in preparation for SIFT-MS analyses

A study of the reactions of H 3O +, NO + and O 2 + ions with two groups of four isobaric, biologically active compounds with molecular weights, MW, of 86u and 88u has been carried out using the selected ion flow tube, SIFT, technique in preparation for the analyses of these compounds in the headspace of bacterial and cell cultures using SIFT-MS. These compounds are: MW 86u: 2,3 butanedione (diacetyl), C 4H 6O 2; allyl ethyl ether, C 5H 10O, cyclopropane carboxylic acid, C 4H 6O 2: γ-butyrolactone, C 4H 6O 2. MW 88u: 3-hydroxybutanone (acetoin), C 4H 8O 2; n-butyric acid, C 4H 8O 2; ethyl acetate, C 4H 8O 2; pyruvic acid, C 3H 4O 3. All 24 reactions proceed at the gas kinetic rate, the dominant primary product ions of the H 3O + reactions being the protonated reactant molecules, MH + with a common mass-to-charge ratio, m/ z, in each group of isobaric compounds; those of the NO + reactions being the adduct ions, NO +M, also with a common m/ z value; for the O 2 + ion reactions, fragmentation ions of the nascent parent ion M + are produced. SIFT-MS analysis of each compound individually is straightforward, but when more than one isobaric compound is present, SIFT-MS analyses become more challenging. However, hydration of some, but not all, of the primary MH + and NO +M primary ions occurs, variously generating MH +(H 2O) 1,2 and NO +MH 2O ions, and the occurrence/non-occurrence of these hydrates can assist in distinguishing between some of the isobaric compounds. From the kinetic data obtained in this study, the required SIFT-MS kinetics library entries for each compound can be constructed that allow their quantification. As an example, SIFT-MS spectra are presented relating to the analysis of the headspace of incubated yoghurt, which show the presence of several volatile organic compounds, including acetoin and diacetyl.

Experimental study of the gas phase chemistry of C 3H 3+ with several cyclic molecules

Rate coefficients and ion product distributions have been determined for the gas phase reactions of C 3H 3 + with several homocyclic and heterocyclic molecules in a selected ion flow tube (SIFT) at 298 K. The rate coefficients for both the linear and cyclic isomers of C 3H 3 + are given. l-C 3 H 3 + reacts by association in the majority of the reactions. c-C 3H 3 + is shown to be more reactive than previously suggested by low pressure experiments. In fact, the cyclic isomer reacts at the gas kinetic rate when the reaction involves a nitrogen containing cyclic compound but is less reactive with oxygen containing cyclic compounds. It is noted this reactivity of both the cyclic and linear isomer should be included when modeling the atmosphere of Titan due to the large number of nitrogen containing molecules that are considered to be present. Currently, the models consider electron recombination to be the only loss channel for c-C 3H 3 +.

Performance and Spectral Tuning of Optically Overtone Pumped Molecular Lasers

A laser model was developed to predict the performance of optically pumped higher overtone molecular lasers under pulsed and continuous wave (CW) excitations. This model takes into account up to 30 rotational levels in each of the eight vibrational states considered. Collision-induced relaxation among rotational levels, vibrational levels, energy transfer to translational degrees of freedom, and interactions with buffer gas, and the temperature dependence of these processes are included. Using parameters for a second overtone pulse pumped HBr laser, a complete lasing cascade can be expected at a certain pump pulse fluence resulting in maximum achievable efficiencies approaching 80%. Optimum operational pressure and temperature conditions are determined by the gas kinetic rates and line broadening effects. Frequency tuning and spectral narrowing of the laser output is possible with the insertion of intracavity filters without sacrificing laser output power owing to efficient energy redistribution between rotational levels mediated by appropriate buffer gases. CW lasing using waveguide (WG) like geometries is possible with efficiencies approaching 92% for first overtone pumped lasers. Heat conduction through the active gas enhanced by buffer gases and subsequent heat dissipation through the cooled WG walls are expected to handle the thermal load up to kW output power levels.

Reactions of N + and N 2+ with several cyclic molecules studied using a selected ion flow tube

A selected ion flow tube, SIFT, has been used to investigate the reactions of N + and N 2 + with four cyclic molecules (pyrrole, pyrrolidine, benzene, and cyclohexane) at 298 K. These species are of particular interest to the chemistry of both Titan's ionosphere and of interstellar molecular clouds. Rate coefficients and product distributions have been determined to provide kinetic data needed for accurate models of these media and establish chemical routes. The majority of reactions proceed at the gas kinetic rate; only pyrrolidine reacts slower. The reactions result mainly in dissociative charge transfer, except the reaction of benzene with N +, in which the major product is non-dissociative charge transfer. Comparisons are made between each neutral with the two reactant ions (N + and N 2 +) of differing recombination energies and also between each reactant ion with neutrals differing in ionization energy and aromaticity. Fragmentation channels are discussed and compared with electron impact ionization.

Gas Phase Reactions of CH3+ with a Series of Homo- and Heterocyclic Molecules

In gas phase ion chemistry, the growth of larger molecules is known to occur through association of ions and neutrals. Where the ion attaches to the neutral is important because it can influence the possibility of additional associations, effectively enabling or terminating further molecular growth. This was investigated by using a Selected Ion Flow Tube (SIFT) at 300 K to study the reactions of CH(3)(+) with the following series of single-ring homocyclic and heterocyclic molecules: benzene (C(6)H(6)), cyclohexane (C(6)H(12)), pyridine (C(5)H(5)N), pyrimidine (C(4)H(4)N(2)), piperidine (C(5)H(11)N), 1,4-dioxane (C(4)H(8)O(2)), furan (C(4)H(4)O), pyrrole (C(4)H(5)N), and pyrrolidine (C(4)H(9)N). Most of the reactions, except for 1,4-dioxane, pyrrole, and pyrrolidine, proceed at the gas kinetic rate. In the ion product distributions, charge transfer, hydride ion abstraction, proton transfer, fragmentation, and association were observed. In particular, proton transfer is seen to be small in all cases even though these channels are energetically favorable. Association is appreciable when the molecules are aromatic (except for furan) and nonexistent when there are no pi electrons in the ring. CH(3)(+) ions are an important intermediate in molecular synthesis in interstellar clouds and in the Titan ionosphere and ring molecules have also been detected in these media. The significance of the studied reactions to these media is discussed.

Ion-Molecule Reactions of Several Ions with Ethylene Oxide and Propenal in a Selected Ion Flow Tube

The selected ion flow tube (SIFT) technique has been used to investigate the ion-molecule reactions of several ions with the neutral molecules ethylene oxide, CH(2)OCH(2)-c, and propenal, CH(2)CHCHO. Both molecules have been identified in hot-core star forming regions [] and have significance to astrochemical models of the interstellar (ISM) and circumstellar medium (CSM). Moreover, the molecules contain functional groups, such as the epoxide group (ethylene oxide) and an aldehyde group, which are part of a conjugated pi-electron system (propenal) whose reactivities have not been studied in detail in gas-phase ion-molecule reactions. The larger recombination energy ions, Ar(+) and N(2)(+), were reacted with the neutrals to give insight into general fragmentation tendencies. These reactions proceeded via dissociative charge-transfer yielding major fragmentation products of CH(3)(+) and HCO(+) for ethylene oxide and CH(2)CH(+) and HCO(+) for propenal. The amino acids glycine and alanine are of particular interest to astrobiology, especially if they can be synthesized in the gas phase. In an attempt to synthesize amino acid precursors, ethylene oxide and propenal were reacted with NH(n)(+) (n = 1-4) and HCNH(+). As might be expected from the proton detachment energies, NH(+), NH(2)(+), and HCNH(+) reacted via proton transfer. NH(3)(+) reacted with each molecule via H-atom abstraction to produce NH(4)(+), and NH(4)(+) reacted via a ternary association. All binary reactions proceeded near the gas kinetic rate. Several associated molecule switching reactions were performed and implications of these reactions to the structures of the association products are discussed Ikeda et al. and Hollis et al.

A selected ion flow tube study of the reactions of various nitrogen containing ions with formic acid, acetic acid, and methyl formate

The possibility of forming organic molecules, such as the amino acid, glycine, from interstellar species through the ion–molecule reactions of ionized amine fragment compounds with neutral carboxylic acid and ester species has been investigated in a selected ion flow tube (SIFT) at 298 K. An earlier study showed that reactions of neutral amine species with ionized carboxylic acid or ester fragments does not result in the desired combination of groups but instead results in the fragmentation of the amines [D.M. Jackson, N.J. Stibrich, N.G. Adams, L.M. Babcock, Int. J. Mass Spectrom. 243 (2005) 115–120]. In the present study, the ion product distributions and reaction rate coefficients of the gas phase reactions of HCOOH, CH 3COOH, and CH 3OCHO with the ions Ar +, N 2 +, NH 2 +, NH 3 +, and HCNH + have been determined. The ions Ar + and N 2 + fragment the neutral species in dissociative charge transfer, and the reactions of NH 2 + and HCNH + with the neutrals result in dissociative proton transfer. NH 3 + reacts with all three species to form NH 4 + by H atom abstraction. The reaction rate coefficients were on average within experimental error of the gas kinetic rate and were on the order of 10 −9 cm 3 s −1.

The abundance of + in diffuse clouds

We used the Plateau de Bure Interferometer to search for λ3mm absorption lines of HOC+ from local diffuse and translucent clouds occulting compact extragalactic mm-wave continuum sources. We detected HOC+ in three directions with column densities only 70-120 times below that of the HCO+ isomer, a factor 5-50 higher than typically found in dense dark gas but comparable to recent observations of dense photon-dominated regions. The observed amounts of HOC+ N(HOC+)/N(H2) can be made in quiescent diffuse gas at thermal gas-kinetic rates if the H2O/OH ratio is of order unity, in mild violation of extant observational limits.

A chemical ionization technique for measurement of pernitric acid in the upper troposphere and the polar boundary layer

The potential of SF6− for the detection of pernitric acid in air by chemical ionization mass spectrometry was studied in the laboratory via its reactions with HO2NO2, O3, H2O, and NO2. Measurements of HO2NO2 using SF6− ion chemistry were then performed at the South Pole. SF6− reacts at the gas kinetic rate with HO2NO2 to form SF5−, NO4−(HF), NO2−(HF), and NO3−. The NO4−(HF) product provides a unique signature for HO2NO2. The rate coefficient for this channel is 2.9 × 10−10 cm³ molecule−1s−1 at 16.5 torr in N2 and decreases as the total pressure increases. NO4−(HF) undergoes ligand switching with H2O and HO2NO2, implying the existence of a NO4− core ion in the gas phase. SF6− reacts with H2O to produce a large number of product ions that increase nonlinearly with [H2O]. This limits the use of SF6− to regions of the atmosphere with low absolute humidities. However, our lab studies indicate that HO2NO2, can be selectively detected in air with an ozone mixing ratio up to 550 ppbv and a dew point of −25°C or less, which corresponds to regions of the troposphere where HO2NO2 is expected to be thermally stable. We present field data from the South Pole showing typical HO2NO2 mixing ratios of 20 pptv.

Fast vibrational relaxation of OH( v=9) by ammonia and ozone

Vibrational relaxation of OH(X 2 Π) in the v=9 state by O 3 and NH 3 has been studied via flash-photolysis using high-resolution direct infrared absorption detection of OH in the v=11←9 band. OH( v=9) removal by O 3 occurs with a nearly gas-kinetic rate (k O 3 =1.37(15)×10 −10 cm 3/ s) . Collisional removal by NH 3 (k NH 3 =7.60(50)×10 −10 cm 3/ s) is two to three times higher than the hard-sphere collision limit, suggesting a resonant V–V energy transfer induced by long-range dipole–dipole interactions. An upper limit of 5×10 −14 cm 3/ s is placed on OH( v=9) vibrational relaxation by argon.

Collisionally induced intramultiplet mixing of Sr(5 3P J) metastable states by He, Ar and Sr ground state atoms

Intramultiplet collisionally induced mixing within the Sr[5s5p( 3P 0,1,2)] manifold is investigated by time-resolved laser-induced fluorescence (LIF) following the pulsed dye-laser generation of Sr( 3P 1) of the electronic ground state {Sr[5s5p( 3P 0,1,2)]←Sr[5s 2( 1S 0)], λ=689.26 nm} at elevated temperatures. The population profiles of the three spin–orbit states were individually monitored by LIF as well as that of Sr( 3P 1) by spontaneous emission at the resonance wavelength. A kinetic model is employed that enables the process of spontaneous emission from Sr( 3P 1) to be isolated initially and characterised by experiment. Particular emphasis is placed on the modelling procedure itself in which the separate kinetic component due to spontaneous emission and the positions of the maxima in the 3P 0 and 3P 2 population profiles constitute severe constraints on the model. The collisional components within the model are reduced to three rate constants where pairs of J states are connected in this context by detailed balance. Thus k 10 and k 12, and, by detailed balance, k 01 and k 21 are quantified at various temperatures and pressures to yield the absolute value of these collision properties for Sr( 3P J ) with He and Ar. Rate data for collisionally induced intramultiplet mixing in Sr( 3P J ) by Sr( 1S 0) itself is also reported found to proceed at close to unit collisional efficiencies in all cases. Thus, at elevated temperatures, variations in atomic profiles are dominated by the differing vapour pressures of atomic strontium. Estimates of the activation energies associated with k 10 and k 12 for the noble gases observed against this large competing background are found to be of the order of the spin–orbit splittings. The model overall is found to be insensitive to k 02 and k 20 whose magnitudes are small by comparison with those for the collisional rate data connecting adjacent J states. Whilst collisional processes for He are some two orders of magnitude more efficient than those for Ar, all of these are seen to be ‘adiabatic’, in contrast with the gas kinetic rate constants of ground Sr, considered to be ‘sudden’ in character. The results are compared with analogous data derived by atomic resonance absorption spectroscopy following pulsed generation of Sr( 3P 1) and are considered in the context of theoretical calculations employing quantum close coupling calculations.

Gas phase reactions of CF 3O − and CF 3O −·H 2O and their relevance to the detection of stratospheric HCl

The reactions of CF 3O −, CF 3O −·H 2O and CF 3O −·HF with HCl and of CF 3O − with H 2O have been studied at room temperature in a flowing afterglow instrument. All reactions with HCl proceed at the gas kinetic rate. The reaction of CF 3O −with HCl proceeds by fluoride transfer, whereas CF 3O −·H 2O and CF 3O −·HF react with HCl by ligand switching. The Gibbs free energy change of the reaction of CF 3O − with H 2O has been determined at room temperature as well as the collisional dissociation rate constant of CF 3O −·H 2O ions.