Photoionization Mass Spectrometer Research Articles

Study on the atmospheric photochemical reaction of CF3 radicals using ultraviolet photoelectron and photoionization mass spectrometer

A study of the atmospheric photochemical reaction of CF3 radical with CO and O2 was performed by using a homemade ultraviolet photoelectron spectrometer-photoionization mass spectrometer (PES-PIMS). The electronic structures and mechanism of ionization and dissociation of CF3OC(O)OOC(O)-OCF3 were investigated. It was indicated that the two bands on the photoelectron spectrum of CF3OC(O)OOC(O)OCF3 are the result of ionization of an electron from a lone pair of oxygen and a fluorine lone pair of CF3 group. The outermost electrons reside in the oxygen lone pair. The experimental and theoretical first vertical ionization energy is 13.21 and 13.178 eV, respectively, with the PES and OVGF method. They are in good agreement. The photo ionization and dissociation processes were discussed with the help of theoretical calculations and PES-PIMS experiment. After ionization, the parent ions prefer the dissociation of the C—O bond and giving the fragments CF3OCO+ and CF3+. It demonstrated that the ultraviolet photoelectron and photoionization mass spectrometer could be applied widely in the study of atmospheric photochemical reaction.

Half-Sandwich Structure of Cyclopentadienyl Dialuminum [Al2(η5-C5H5)] from Pulsed-Field Ionization Electron Spectroscopy and ab Initio Calculations

Cyclopentadienyl dialuminum [Al2Cp, Cp = C5H5] was prepared in a pulsed laser ablation cluster beam source and identified with a time-of-flight photoionization mass spectrometer. The high-resolution electron spectrum of this complex was obtained using pulsed-field ionization zero electron kinetic energy (ZEKE) photoelectron spectroscopy. Three isomeric structures with two Al atoms residing on the same or opposite sites of the Cp plane were predicted by second-order Møller-Plesset perturbation theory. A half-sandwich structure with an aluminum dimer perpendicular to the Cp plane was identified by the experiment. The ground electronic states of the neutral and ionized species are 2A' ' in Cs symmetry and 1A1 in C5v symmetry, respectively. In both the neutral and ionic states, one of the Al2 atoms binds with five carbons, and the metal-ligand bonding consists of orbital and electrostatic contributions. Ionization of the 2A' ' neutral state enhances the metal-ligand bonding but weakens the metal-metal interaction.

Identification of combustion intermediates in isomeric fuel-rich premixed butanol–oxygen flames at low pressure

Laminar premixed low-pressure flames fueled by either one of the four isomers of butanol were investigated by a molecular-beam photoionization mass spectrometer using vacuum ultraviolet (VUV) synchrotron radiation as the ionization source. The photoionization efficiency (PIE) spectra of most flame intermediates were measured between 7.75 and 11.00 eV. By comparing the resulting PIE spectra to known ionization energies (IEs) or known PIE spectra of pure substances, most hydrocarbon and oxygenated combustion intermediates, including some radicals, in the mass range from m / z = 15 to 106 were assigned and identified in the four butanol flames. The results show that the higher-mass oxygenated species in butanol flames are strongly affected by the fuel structure, while many hydrocarbon isomers appear almost independent of the fuel structure. The respective dissociation mechanisms of the fuels, including complex fission, simple fission, and H-atom abstraction, are in good agreement with previous results from nonpremixed butanol flames.

Kinetics of the CH 3 + HCl/DCl → CH 4/CH 3D + Cl and CD 3 + HCl/DCl → CD 3H/CD 4 + Cl reactions: An experimental H atom tunneling investigation

The kinetics of the radical reactions of CH 3 with HCl or DCl and CD 3 with HCl or DCl have been investigated in a temperature controlled tubular reactor coupled to a photoionization mass spectrometer. The CH 3 (or CD 3) radical, R, was produced homogeneously in the reactor by a pulsed 193 nm exciplex laser photolysis of CH 3COCH 3 (or CD 3COCD 3). The decay of CH 3/CD 3 was monitored as a function of HCl/DCl concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature, typically from 188 to 500 K. The rate constants of the CH 3 and CD 3 reactions with HCl had strong non-Arrhenius behavior at low temperatures. The rate constants were fitted to a modified Arrhenius expression k = QA exp (− E a/ RT) (error limits stated are 1 σ + Students t values, units in cm 3 molecule −1 s −1): k(CH 3 + HCl) = [1.004 + 85.64 exp (−0.02438 × T/K)] × (3.3 ± 1.3) × 10 −13 exp [−(4.8 ± 0.6) kJ mol −1/ RT] and k(CD 3 + HCl) = [1.002 + 73.31 exp (−0.02505 × T/K)] × (2.7 ± 1.2) × 10 −13 exp [−(3.5 ± 0.5) kJ mol −1/ RT]. The radical reactions with DCl were studied separately over a wide ranges of temperatures and in these temperature ranges the rate constants determined were fitted to a conventional Arrhenius expression k = A exp (− E a/ RT) (error limits stated are 1 σ + Students t values, units in cm 3 molecule −1 s −1): k(CH 3 + DCl) = (2.4 ± 1.6) × 10 −13 exp [−(7.8 ± 1.4) kJ mol −1/ RT] and k(CD 3 + DCl) = (1.2 ± 0.4) × 10 −13 exp [−(5.2 ± 0.2) kJ mol −1/ RT] cm 3 molecule −1 s −1. Curvature in the Arrhenius plots of the H-atom abstraction reactions at low temperatures was analyzed by considering H-atom tunneling through the reaction barrier and primary kinetic isotope effect. Contribution of tunneling in it was concluded to be negligible. In addition, secondary isotope effect was measured.

Photoionization mass spectrometry and modeling studies of the chemistry of fuel-rich dimethyl ether flames

Reaction paths are identified for dimethyl ether (DME) combustion using modeling of new data from fuel-rich DME flat flames. A molecular-beam flame-sampling photoionization mass spectrometer, employing VUV synchrotron radiation, is applied to the measurement of mole fractions for 21 flame species in low-pressure premixed fuel-rich ( Φ = 1.2, 1.68) DME/oxygen/argon flat flames. This approach is capable of resolving and identifying isomers and other flame species of near equal masses with ionization thresholds that differ by as little as 0.1 eV. The measurements agree well with flame modeling predictions, using a recently revised high-temperature DME kinetic mechanism, which identify reaction paths quite analogous to alkane combustion. They further reveal the presence of ethyl methyl ether, a molecule previously unobserved in flames and not included in present flame models.

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

The kinetics of the reactions of CH2Br and CH2I radicals with O2 have been studied in direct measurements using a tubular flow reactor coupled to a photoionization mass spectrometer. The radicals have been homogeneously generated by pulsed laser photolysis of appropriate precursors at 193 or 248 nm. Decays of radical concentrations have been monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions with the amount of O2 being in large excess over radical concentrations. No buffer gas density dependence was observed for the CH2I + O2 reaction in the range 0.2-15 x 10(17) cm(-3) of He at 298 K. In this same density range the CH2Br + O2 reaction was obtained to be in the third-body and fall-off area. Measured bimolecular rate coefficient of the CH2I + O2 reaction is found to depend on temperature as k(CH2I + O2)=(1.39 +/- 0.01)x 10(-12)(T/300 K)(-1.55 +/- 0.06) cm3 s(-1)(220-450 K). Obtained primary products of this reaction are I atom and IO radical and the yield of I-atom is significant. The rate coefficient and temperature dependence of the CH2Br + O2 reaction in the third-body region is k(CH2Br + O2+ He)=(1.2 +/- 0.2)x 10(-30)(T/300 K)(-4.8 +/- 0.3) cm6 s(-1)(241-363 K), which was obtained by fitting the complete data set simultaneously to a Troe expression with the F(cent) value of 0.4. Estimated overall uncertainties in the measured reaction rate coefficients are about +/-25%.

Modification of photoionization mass spectrometer with synchrotron radiation as ionization source

In this article we introduce a modification on ion optics of a reflectron time-of-flight mass spectrometer for the study of flame chemistry with synchrotron radiation as a continuous ionization source. A small bias voltage is used in the extraction region to simultaneously reduce the background ion signal, eliminate secondary ionization process caused by photoelectrons, increase the ion detection efficiency, and improve the mass resolution.

Photoionization mass spectrometer for studies of flame chemistry with a synchrotron light source

A flame-sampling molecular-beam photoionization mass spectrometer, recently designed and constructed for use with a synchrotron-radiation light source, provides significant improvements over previous molecular-beam mass spectrometers that have employed either electron-impact ionization or vacuum ultraviolet laser photoionization. These include superior signal-to-noise ratio, soft ionization, and photon energies easily and precisely tunable [E∕ΔE(FWHM)≈250–400] over the 7.8–17-eV range required for quantitative measurements of the concentrations and isomeric compositions of flame species. Mass resolution of the time-of-flight mass spectrometer is m∕Δm=400 and sensitivity reaches ppm levels. The design of the instrument and its advantages for studies of flame chemistry are discussed.

Kinetics of the Reactions of Chlorinated Methyl Radicals (CH2Cl, CHCl2, and CCl3) with NO2 in the Temperature Range 220−360 K

The kinetics of the reactions of chlorinated methyl radicals (CH2Cl, CHCl2, and CCl3) with NO2 have been studied in direct measurements at temperatures between 220 and 360 K using a tubular flow reactor coupled to a photoionization mass spectrometer. The radicals have been homogeneously generated at 193 or 248 nm by pulsed laser photolysis of appropriate precursors. Decays of radical concentrations have been monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions with the amount of NO2 being in large excess over radical concentrations. The bimolecular rate coefficients of all three reactions are independent of the bath gas (He or N2) and pressure within the experimental range (1-6 Torr) and are found to depend on temperature as follows: k(CH2Cl + NO2) = (2.16 +/- 0.08) x 10(-11) (T/300 K)(-1.12+/-0.24) cm3 molecule(-1) s(-1) (220-363 K), k(CHCl2 + NO2) = (8.90 +/- 0.16) x 10(-12) (T/300 K)(-1.48+/-0.13) cm3 molecule(-1) s(-1) (220-363 K), and k(CCl3 + NO2) = (3.35 +/- 0.10) x 10(-12) (T/300 K)(-2.2+/-0.4) cm3 molecule(-1) s(-1) (298-363 K), with the uncertainties given as one-standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are about +/-25%. In the reactions CH2Cl + NO2, CHCl2 + NO2, and CCl3 + NO2, the products observed are formaldehyde, CHClO, and phosgene (CCl2O), respectively. In addition, a weak signal for the HCl formation has been detected for the CHCl2 + NO2 reaction.

Mass spectrometry up to 1 million mass units for the simultaneous detection of primary soot and of soot precursors (nanoparticles) in flames

A hybrid setup consisting of low pressure burner, flow reactor and photo-ionization mass spectrometer was used for the simultaneous detection of primary soot and of flame generated nanoparticles precursing soot. The studied flames were low pressure (120–180 mbar) C 2H 4/O 2 flames surrounded by an N 2 shield. The flow reactor was not used in this study. Through variation of the burner conditions (stoichiometry, sampling height) it could be shown that nanoparticles and soot are entirely independent species. The former, in particular, are found very early in the flame and their concentration profiles do not vary very much throughout the flame. This renders the possibility that nanoparticles are emitted together with soot and consequently may constitute an additional environmental hazard. Photo-ionization mass spectrometry is well suited for the detection of these particles.

Kinetics of the Reactions of Vinyl (C2H3) and Propargyl (C3H3) Radicals with NO2 in the Temperature Range 220−340 K

The kinetics of the reactions of vinyl (C2H3) and propargyl (C3H3) radicals with NO2 have been studied in direct measurements at temperatures between 220 and 340 K, using a tubular flow reactor coupled to a photoionization mass spectrometer. The vinyl and propargyl radicals have been homogeneously generated at 193 nm by the pulsed laser photolysis of methyl vinyl ketone (vinyl bromide) and propargyl chloride, respectively. Decays of radical concentrations have been monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions with the amount of NO2 being in large excess over radical concentrations. The bimolecular rate coefficients of both reactions are independent of the bath gas (He or N2) and pressure within the experimental range (1−7 Torr) and are found to depend on temperature as follows: k(C2H3 + NO2) = [(4.19 ± 0.05) × 10-11](T/300 K)-0.60 ± 0.07 cm3 molecule-1 s-1 and k(C3H3 + NO2) = [(2.55 ± 0.05) × 10-11](T/300 K)-1.06 ± 0.10 cm3 molecule-...

Photoionization of Nb3CO and Nb3(CO)2: Is CO Molecularly or Dissociatively Adsorbed on Niobium?

The photoionization efficiency spectra of gas-phase Nb3CO and Nb3(CO)2 have been acquired using a laser-ablation, photoionization mass spectrometer. The adiabatic ionization energies of the species are 5.82 ± 0.02 and 5.85 ± 0.02 eV, respectively, where error bars reflect precision, the values are accurate to within 0.1 eV. From these data and literature values of cation bond strengths, the bond energies of Nb3-CO and Nb3CO-CO are found to lie within the 2.8-3.4 and 1.7-1.8 eV ranges, respectively. The former is most consistent with dissociatively adsorbed CO, while the latter may correspond to molecularly or dissociatively adsorbed CO. These conclusions are supported by density-functional theory calculations. In addition to properties of Nb3CO, the properties of the transition state to dissociative adsorption of CO have been calculated. It is found that the transition state lies lower in energy than the separated reagents. Spontaneous dissociation is expected to follow molecular adsorption of CO on Nb3, accordingly. Over the 1540-2220 cm-1 range, no infrared multiphoton dissociation of Nb3CO or Nb3(CO)2 is observed, consistent with CO being dissociatively adsorbed for both species.

Kinetics of the R + HBr ⇄ RH + Br (R = CH2Br, CHBrCl or CCl3) equilibrium. Thermochemistry of the CH2Br and CHBrCl radicals

The kinetics of the reaction of the CH2Br, CHBrCl or CCl3 radicals, R, with HBr have been investigated separately in a heatable tubular reactor coupled to a photoionization mass spectrometer. The CH2Br (or CHBrCl or CCl3) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH2Br2 (or CHBr2Cl or CBrCl3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately over a wide ranges of temperatures and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student’s t values, units in cm3 molecule−1 s−1): k(CH2Br + HBr) = (7.5 ± 0.9) × 10−13 exp[−(2.53 ± 0.13) kJ mol−1/RT], k(CHBrCl + HBr) = (4.9 ± 1.1) × 10−13 exp[−(8.2 ± 0.3) kJ mol−1/RT] and k(CCl3 + HBr) < (6 ± 1) × 10−15 at 787 K. The kinetics of the reverse reactions, Br + R′H → HBr + R′ (R′ = CH2Br or CHBrCl), were taken from the literature and also calculated by ab initio methods at the MP2(fc)/6-31G(d,p)//MP2(fc)/6-31G(d,p) level of theory in conjunction with the thermodynamic transition state theory to calculate the entropy and the enthalpy of formation values of the radicals studied. The thermodynamic values were obtained at 298 K using a second-law method. The results for entropy values are as follows (units in J K−1 mol−1): 263 ± 7 (CH2Br) and 294 ± 6 (CHBrCl). The results for enthalpy of formation values at 298 K are (in kJ mol−1): 171.1 ± 2.7 (CH2Br) and 143 ± 6 (CHBrCl). The C–H bond strength of analogous halomethanes are (in kJ mol−1): 427.2 ± 2.4 (CH3Br) and 406.0 ± 2.4 (CH2BrCl). Thermodynamic properties of the CH2Br radical were calculated by statistical thermodynamic methods over the temperature range 100–1500 K.

Rate coefficient for the reaction of CCl3 radicals with ozone

AbstractThe rate coefficient for the reaction of CCl3 radicals with ozone has been measured at 303 ± 2 K. The CCl3 radicals were generated by the pulsed laser photolysis of carbon tetrachloride at 193 nm. The time profile of CCl3 concentration was monitored with a photoionization mass spectrometer. Addition of the O3–O2 mixture to this system caused a decay of the CCl3 concentration because of the reactions of CCl3 + O3 → products (5) and CCl3 + O2 → products (4). The decay of signals from the CCl3 radical was measured in the presence and absence of ozone. In the absence of ozone, the O3–O2 mixture was passed through a heated quartz tube to convert the ozone to molecular oxygen. Since the rate coefficient for the reaction of CCl3 + O2 could be determined separately, the absolute rate coefficient for reaction (5) was obtained from the competition among these reactions. The rate coefficient determined for reaction (5) was (8.6 ± 0.5) × 10−13 cm3 molecule−1 s−1 and was also found to be independent of the total pressure (253–880 Pa of N2). This result shows that the reaction of CCl3 with O3 cannot compete with its reaction with O2 in the ozone layer. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 310–316, 2003

Kinetics of the reactions of vinyl radicals with molecular oxygen and chlorine at temperatures 200–362 K

The kinetics of the C2H3 + O2 and C2H3 + Cl2 reactions have been studied in direct measurements at temperatures between 200–362 K using a tubular flow reactor coupled to a photoionization mass spectrometer (PIMS). The vinyl radicals were homogeneously generated by the pulsed laser photolysis of methyl vinyl ketone at 193 nm. The subsequent decays of the radical concentrations were monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions. Reaction products identified were HCO and H2CO for the oxygen reaction and C2H3Cl for the chlorine reaction, respectively. The rate coefficients of both reactions were independent of the bath gases (He or N2) and pressures within the experimental range, 0.13–0.53 kPa, and can be expressed by the Arrhenius equations k(C2H3 + O2) = (4.62 ± 0.40) × 10−12exp(1.41 ± 0.18 kJ mol−1/RT) cm3 molecule−1 s−1 and k(C2H3 + Cl2) = (4.64 ± 0.59) × 10−12exp(3.12 ± 0.27 kJ mol−1/RT) cm3 molecule−1 s−1, where uncertainties are one standard deviation. These experimental results obtained by using our new apparatus are in good agreement with previous direct measurements.

State-Selected and State-to-State Ion−Molecule Reaction Dynamics

A unique triple-quadrupole double-octopole (TQDO) photoionization mass spectrometer has been developed for total cross section measurements of state-selected ion−molecule reactions. By employing this TQDO apparatus, we have recently examined the absolute total cross sections for a series of state-selected ion−molecule reactions involving Ar+(2P3/2,1/2), O+(4S, 2D, 2P), and organosulfur ions (CH3SH+, CH3CH2SH+, and CH3SCH3+) in their ground states. The cross section measurements, together with product ion kinetic energy analyses, have provided convincing evidence that the Ar+(2P3/2,1/2) + CO2 (CO, N2, O2) reactions proceed via a charge-transfer predissociation mechanism. The comparison of absolute cross sections for product ions formed in the dissociative charge transfer of Ar+(2P3/2,1/2) + CO2 (CO, N2, O2) and those produced in photoionization of CO2 (CO, N2, O2) suggests that product ions formed by dissociative charge transfer are also produced by photoionization via a similar set of excited predissociative states of CO2+ (CO+, N2+, O2+). By preparing CH3SH+, CH3CH2SH+, and CH3SCH3+ in their ground states by photoionization of the corresponding neutrals, we have examined the dissociation of these ions via collision activation. Equipped with two radio frequency octopole ion guide reaction gas cells, the TQDO apparatus has allowed the identification of the isomeric structure of product ions by using the charge-transfer probing method. Strong preference is observed for C−S and C−C bond scissions, leading to the formation of CH3+ from CH3SH+, CH3CH2+, and CH2SH+ from CH3CH2SH+, and CH3S+ from CH3SCH3+ as compared to C−H and S−H bond breakages. The observation of these bond selective dissociation reactions is contrary to that found in photoionization of CH3SH, CH3CH2SH, and CH3SCH3 and is indicative of nonstatistical behavior for collision-induced dissociation of these organosulfur ions. An application of the radio frequency ion-guide for state-selection of O+(4S, 2D, 2P) prepared by the dissociative charge-transfer reactions of He+ (Ne+, Ar+) + O2 is described. The success of this method has made possible the absolute total cross section measurement of the state-selected ion−molecule reactions O+(4S, 2D, 2P) + N2 (O2, H2, D2, CO2, H2O), which are considered as the most important set of reactions in the Earth's ionosphere.

Kinetics of the R + HBr → RH + Br (R = CH2I or CH3) reaction. An ab initio study of the enthalpy of formation of the CH2I, CHI2 and CI3 radicals

The kinetics of the reaction of the CH2I and CH3 radicals, R, with HBr have been investigated separately in a heatable tubular reactor coupled to a photoionization mass spectrometer. The CH2I (or CH3) radical was produced homogeneously in the reactor by a pulsed 248 or 351 nm exciplex laser photolysis of CH2I2 (or CH3I). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately over a wide ranges of temperatures and the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student's t values, units in cm3 molecule−1 s−1): k(CH2I + HBr) = (3.8 ± 0.7) × 10−13exp[ + (1.4 ± 0.6) kJ mol−1/RT] and k(CH3 + HBr) = (2.3 ± 0.5) × 10−12 exp[ + (0.60 ± 0.17) kJ mol−1/RT]. The threshold energies of the reverse reactions, Br + R′H → R′ + HBr (R′ = CH2I, CHI2 or CI3), were calculated by ab initio methods at the MP2(fc)/6-311G(df)//MP2(fc)/6-311G(df) level of theory. These were combined with the experimentally determined activation energies of the forward reactions in a second-law method to determine the enthalpies of the reactions. The enthalpy of formation values at 298 K are (in kJ mol−1): 228.0 ± 2.8 (CH2I), 314.4 ± 3.3 (CHI2) and 424.9 ± 2.8 (CI3). The C–H bond strengths of analogous iodomethanes are (in kJ mol−1): 431.6 ± 2.8 (CH3I), 412.9 ± 3.3 (CH2I2) and 391.9 ± 3.1 (CHI3). The Arrhenius expression of the reverse reactions as determined by the thermodynamic transition state theory. The entropies of activation of the reactions were obtained by ab initio calculations.

Photoionization study of CH3SCH2Cl formed in the reaction system Cl/Cl2/CH3SCH3

A photoionization-efficiency spectrum of CH3SCH2Cl was measured over the wavelength range 108–142 nm by means of a photoionization mass spectrometer coupled to a synchrotron as the source of radiation. Gaseous CH3SCH2Cl was generated in a discharge-flow reactor involving Cl, Cl2, and CH3SCH3 at room temperature via these sequential reactions: Cl+CH3SCH3→CH3SCH2+HCl; CH3SCH2+Cl2→CH3SCH2Cl+Cl. According to the PIE spectrum of CH3SCH2Cl thus obtained, the ionization energy is (9.077±0.007) eV. Based on GAUSSIAN-2 calculations, the observed ionization of CH3SCH2Cl near the threshold region is likely to form from singlet CH3SCH2Cl ionizing to doublet CH3SCH2Cl+; the calculated ionization energy 9.064 eV agrees with the experimental value. The adiabatic ionization energy of CH3SCH2 and appearance energy of CH3SCH2+ from CH3SCH2Cl were determined to be (6.884±0.008) eV and (10.007±0.016) eV, respectively; the dissociation energy of the CH3SCH2–Cl bond is thus derived to be (72.0±0.6) kcal mol−1.

Kinetics of the Reaction of the CHCl2 Radical with Oxygen Atoms

The kinetics of the reaction of CHCl2 radical with O(3P) atoms has been studied in a heatable tubular reactor coupled to a photoionization mass spectrometer. The time-resolved decay of CHCl2 was monitored as a function of O atom concentration (in a large excess of O atoms). The rate constants show a weak dependence on temperature over the 302−900 K range and can be represented by an Arrhenius expression k(T) = k3 = (9.00 ± 0.92) × 10-11exp(57.4 ± 19.1 K/T) cm3 molecule-1 s-1. HCl was detected as a product of the CHCl2 + O(3P) reaction.

Uptake of acetone into sulfuric‐acid solutions

A time‐dependent uptake of acetone into sulfuric‐acid solutions was observed by means of a wetted‐wall flow reactor coupled to a photoionization mass spectrometer. The uptake was found to be reversible, and no reactive loss of acetone was observed. Henry's law constants of acetone into sulfuric‐acid were obtained from the time‐dependent uptake behavior observed for 50–79 wt% of H2SO4 solution at temperatures between 230 – 270 K. It was found that the solubility of acetone was mainly governed by its protonation in the acid. The observed Henry's law constant would unlikely be high enough to remove acetone efficiently from the gas phase in the upper troposphere; in addition, the reaction probability due to a sulfate‐mediated condensation was found to be too low.