Production Of Cl Research Articles

Framework for Operational Performance Measurements in Small and Medium Scale Industries Using Discrete Event Simulation Approach

Globally, production systems must cope with limitations arising from variabilities and complexities due to globalization and technological advancements. To survive in spite of these challenges, critical process measures need to be closely monitored to ensure improved system performance. For production managers, the availability of accurate measurements which depict the status of production activities in real time is desired. This study is designed to develop an operational data decision support tool (ODATA-DST) using discrete event simulation approach. The work-in-process and processing time of each workstation/buffer station in a bottled water production system were investigated. The status of each job as they move through the system was used to simulate a routing matrix. The production output data for 50cl and 75cl product from 2014-2016 were collected. A mathematical model for routing jobs from the point of arrival to the point of departure was developed using discrete event simulation. A graphical user interface (GUI) was designed based on the factory’s performance measurement algorithm. Simulating the factory’s work-in-process with respect to internal benchmarks yielded a cycle time of 4.4, 6.23, 5.04 and throughput of 0.645, 0.455, 0.637 for best case scenario, worst case scenario and practical worst case scenario respectively. The factory performed below the simulated benchmark at 26%, 28%, 28% for the 50cl and at 51%, 54%, 59% for 75cl regarding the year 2014, 2015 and 2017 respectively. Performance measurement decision support tool has been developed to enhance the production manager’s decision making capability. The tool can improve production data analysis and performance predictions.

Longitudinal profiles of relaxin and progestagens during pregnancy, pregnancy loss and false pregnancy in the killer whale (Orcinus orca)

The circulating pattern of immunoreactive relaxin and progestagens based on monthly and gestational stage (early, mid, late) profiles were determined during pregnancies that resulted in live calves (LIVE, n = 30), stillbirths (STILLB, n = 3), abortions (ABORT, n = 5) and presumptive false pregnancies (FALSE, n = 8), and during the follicular (n = 34) and luteal phase (n = 58). Monthly LIVE relaxin concentrations steadily increased during gestation, but values did not significantly exceed those of the luteal phase until 9 months prior to parturition, peaking during the final month at 2356 ng/ml. Relaxin surged (P < 0.05) during the final week of gestation (36,397 ng/ml), undergoing a 3 and 9-fold increase compared with concentrations in the preceding two weeks, respectively. Monthly relaxin production did not differ among each reproductive state with the exception of months-13–16 where concentrations were higher (P < 0.001) for STILLB than LIVE. Relaxin concentration was reduced (P < 0.0001) by 849% in placental versus maternal serum collected within 1 day of labor. Mid- and late-pregnancy progestagen concentrations were lower for FALSE (P < 0.001) compared with STILLB and LIVE. Late pregnancy progestagen concentrations were reduced for FALSE (P < 0.05) and ABORT (P < 0.02) compared with LIVE and STILLB. Monthly progestagen production in ABORT tended to be lower than LIVE across a range of gestational months (Months 2, 7, 8, 11) but this difference only became significant during months 14 and 15. Results indicate that relaxin is primarily produced by the CL during pregnancy, and that concentrations could not be used to differentiate from non-pregnant females until the final 6 months of gestation. In addition, as would be expected from a primarily CL product, relaxin cannot be used to detect abnormal pregnancies. Conversely, progestagens, which are produced by both the placenta and CL can be used to differentiate FALSE from normal pregnancy and may be useful indicators of fetal health in the killer whale.

Heterogeneous production of Cl2 from particulate chloride: Effects of composition and relative humidity

Reactions initiated by chlorine atoms can enhance the formation of ozone (O3) and secondary organic aerosol (SOA) in the troposphere. Environmental chamber experiments were conducted to quantify heterogeneous Cl2 production from NH4Cl and NaCl particles exposed to O3 and hydroxyl radicals (•OH). Observations are inconsistent with models of Cl2 production resulting solely from surface‐mediated reactions of •OH and suggest that O3 plays a significant role. The production of Cl2 increased with relative humidity and decreased in the presence of SOA or nitric oxides (NOx). Heterogeneous reactive uptake coefficients for the production of Cl2 from O3 on pure NH4Cl ( ) averaged 1.4 ± 1.0 × 10−3. Cl2 production was six times more efficient on NH4Cl aerosol than on NaCl aerosol. Model calculations under atmospheric conditions suggest this heterogeneous Cl2 production could increase peak daily O3 concentrations by over 10%. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3151–3158, 2018

Time-dependent evolution of the dichloromethane-mediated Bi2MoO6/BiOCl heterojunction for enhanced electrochemical performance

In this work, we presented a one-pot hydrothermal approach to produce Bi2MoO6/BiOCl heterojunction in the presence of dichloromethane (CH2Cl2) as the source of chloridion (Cl−) through alcoholysis. The gradual production of Cl− can elaborately manipulate the composites’ morphology leading to the time-controlled assembly of BiOCl nanosheets onto Bi2MoO6 surface; a pronounced Bi2MoO6/BiOCl heterojunction was observed with prolonged reaction time. The Bi2MoO6/BiOCl composites obtained at 6 h exhibited the highest specific capacitance of 651 F g−1 at 1 A g−1, meanwhile, the specific capacitance could be retained at ∼85% after 5000 cycles at a current of 4 A g−1, rendering this Bi2MoO6/BiOCl heterojunction as a promising electrode material for supercapacitors.

Atmospheric fate of hydrofluoroolefins, CxF2x+1CH[dbnd]CH2 (x = 1,2,3,4 and 6): Kinetics with Cl atoms and products

Rate coefficients for the gas-phase reactions of CxF2x+1CHCH2 (x = 1, 2, 3, 4 and 6) with Cl atoms were determined at (298 ± 2) K and (710 ± 5) Torr of air using a relative rate technique. Two experimental setups with simulation chambers were employed with Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography coupled to Mass Spectrometry (GC-MS) as detection techniques. The Cl-rate coefficients obtained were (in 10−10 cm3 molecule−1 s−1): (0.85 ± 0.11) for CF3CHCH2, (1.11 ± 0.08) for C2F5CHCH2, (1.12 ± 0.18) for C3F7CHCH2, (0.97 ± 0.09) for C4F9CHCH2, and (0.99 ± 0.08) for C6F13CHCH2. Additionally, the gas-phase products were identified and quantified, when possible, by FTIR spectroscopy or GC-MS. The main reaction product was reported to be CxF2x+1C(O)CH2Cl. The fluorinated species, CxF2x+1CHO and CxF2x+1C(O)CH2Cl, were identified. CF3C(O)CH2Cl and CF3CHO were found to be formed with molar yield of (69 ± 5)% and (9 ± 1)%, respectively. The global lifetime of the investigated CxF2x+1CHCH2 due to their Cl-reaction is more than 100 days so this route does not compete with the removal by OH radicals. This lifetime is long enough for CxF2x+1CHCH2 to be transported to remote areas where they can be degraded. However, at a local scale, in marine regions at dawn the removal of CxF2x+1CHCH2 is expected to occur in ca. 1 day. The atmospheric degradation of these hydrofluoroolefins by Cl atoms is not expected to be a source of bioaccumulative perfluorinated carboxylic acids, CxF2x+1C(O)OH. Additionally, the UV absorption cross sections of CF3C(O)CH2Cl were determined together with the rate coefficient of the OH reaction by an absolute kinetic method at room temperature.

Numerical study of capacitive coupled HBr/Cl2 plasma discharge for dry etch applications

HBr/Cl2 plasma discharge is investigated to study the etchant chemistry of this discharge by using the self-consistent fluid model. A comprehensive set of gas phase reactions (83 reactions) including primary processes such as excitation, dissociation, and ionization are considered in the model along with 24 species. Our findings illustrate that the densities of neutral species (i.e., Br, HCl, Cl, H, and H2) produced in the reactor are higher than charged species (i.e., Cl2+, Cl−, HBr+, and Cl+). Density profile of neutral and charged species followed bell shaped and double humped distributions, respectively. Increasing Cl2 fraction in the feedback gases (HBr/Cl2 from 90/10 to 10/90) promoted the production of Cl, Cl+, and Cl2+ in the plasma, indicating that chemical etching pathway may be preferred at high Cl-environment. These findings pave the way towards controlling/optimizing the Si-etching process.

Unraveling the Mechanism and Regioselectivity of the B12-Dependent Reductive Dehalogenase PceA.

PceA is a cobalamin-dependent reductive dehalogenase that catalyzes the dechlorination of perchloroethylene to trichloroethylene and then to cis-dichloroethylene as the sole final product. The reaction mechanism and the regioselectivity of this enzyme are investigated by using density functional calculations. Four different substrates, namely, perchloroethylene, trichloroethylene, cis-dichloroethylene, and chlorotheylene, have been considered and were found to follow the same reaction mechanism pattern. The reaction starts with the reduction of Co(II) to Co(I) through a proton-coupled electron transfer process, with the proton delivered to a Tyr246 anion. This is followed by concerted C-Cl bond heterolytic cleavage and proton transfer from Tyr246 to the substrate carbon atom, generating a Co(III) -Cl intermediate. Subsequently, a one-electron transfer leads to the formation of the Co(II) -Cl product, from which the chloride and the dehalogenated product can be released from the active site. The substrate reactivity follows the trend perchloroethylene>trichloroethylene≫cis-dichloroethylene≫chlorotheylene. The barriers for the latter two substrates are significantly higher compared with those for perchloroethylene and trichloroethylene, implying that PceA does not catalyze their degradation. In addition, the formation of cis-dichloroethylene has a lower barrier by 3.8 kcal mol(-1) than the formation of trans-dichloroethylene and 1,1-dichloroethylene, reproducing the regioselectivity. These results agree quite well with the experimental findings, which show cis-dichloroethylene as the sole product in the PceA-catalyzed dechlorination of perchloethylene and trichloroethylene.

Report on the Photochemical Induced Halogen Activation of Fecontaining Aerosols

Iron (Fe) occurs in minerals and highly saline media (e.g., sea salt aerosol, salt brines etc.) and induces photochemical processes. High salinity, low pH, and organic constituents promote the dissolution of iron, forming photosensitive complexes that are responsible for a production of gaseous Cl atoms when irradiated by sunlight. We studied the production of atomic Cl, Br and OH radicals from modeled salt pans and artificial sea-salt aerosols containing Fe(III) ions or pyrogenic Fe2O3 particles (Sicotrans Orange, BASF) at various compositions in a Teflon smog-chamber. The samples were either spread on a Teflon sheet or they were nebulized from dilute brines (most abundant particle diameter: ~0.4 μm, initial surface area: up to 3·10-2cm2cm-3) and exposed to simulated sunlight at 60-90% relative humidity. The photochemical formation of Cl, OH (and Br if possible) in the gas phase was quantified by the radical clock method resulting in time profiles of the radical-production rates and total productions. Simultaneous monitoring of the aerosol surface area enabled us to determine the initial Cl production rate per cm2 aerosol surface. Whereas no significant Cl production was detected employing a molar Cl-/Fe(III) ratio of 955, the rate increased to ~2.8·1017 atoms cm-2 s-1 (at a ratio of 101), ~4.1·1017 atoms cm-2 s-1 (at a ratio of 53) and ~1.9·1018 atoms cm-2 s-1 (at a ratio of 13). The presence of NO2 (~20 ppb) or O3 (630 ppb) in the gas phase additionally increased the Fe(III)-induced chloride activation to ~7·1018 atoms cm-2 s-1 and ~9·1018 atoms cm-2 s-1 (at a Cl-/Fe(III) ratio of 13), respectively. SO2 slightly restrained the Cl formation. Artificial sea salt aerosols doped with Fe2O3 particles (Cl-/Fetot~13) did not result in detectable Cl concentrations. However, decreasing the pH below 2 favored the dissolution of Fe and led to Cl production rates comparable to the Fe(III) experiments (~7·1018 atoms cm-2 s-1) whereas accelerating the erosion of the particles by freezing and thawing did not lead to detectable results. These observations are in accord with the speciation of the photolabile, aqueous Fe(III) complexes obtained from an equilibrium model (PHREEQC). The aerosol experiments result in much higher effective Cl production rates with ~50% of active Fe(III) in zero air, as compared to the previous salt-pan experiments in the same Teflon smog-chamber with a portion of 0.05-0.07% of active Fe(III)). This is caused by the larger active surface area of the homogeneously distributed aerosols.

Dechlorination of polychlorinated biphenyls by iron and its oxides

The decomposition efficiency of polychlorinated biphenyls (PCBs) was determined using elemental iron (Fe) and three iron (hydr)oxides, i.e., α-Fe2O3, Fe3O4, and α-FeOOH, as catalysts. The experiments were performed using four distinct PCB congeners (PCB-209, PCB-153, and the coplanar PCB-167 and PCB-77) at temperatures ranging from 180°C to 380°C and under an inert, oxidizing or reducing atmosphere composed of N2, N2+O2, or N2+H2. From these three options N2 showed to provide the best reaction atmosphere. Among the iron compounds tested, Fe3O4 showed the highest activity for decomposing PCBs. The decomposition efficiencies of PCB-209, PCB-167, PCB-153, and PCB-77 by Fe3O4 in an N2 atmosphere at 230°C were 88.5%, 82.5%, 69.9%, and 66.4%, respectively. Other inorganic chlorine (Cl) products which were measured by the amount of inorganic Cl ions represented 82.5% and 76.1% of the reaction products, showing that ring cleavage of PCBs was the main elimination process. Moreover, the dechlorination did not require a particular hydrogen donor. We used X-ray photoelectron spectroscopy to analyze the elemental distribution at the catalyst’s surface. The O/Fe ratio influenced upon the decomposition efficiency of PCBs: the lower this ratio, the higher the decomposition efficiency. X-ray absorption near edge structure spectra showed that α-Fe2O3 effectively worked as a catalyst, while Fe3O4 and α-FeOOH were consumed as reactants, as their final state is different from their initial state. Finally, a decomposition pathway was postulated in which the Cl atoms in ortho-positions were more difficult to eliminate than those in the para- or meta-positions.

Iron(III)-induced activation of chloride from artificial sea-salt aerosol

Environmental context Inorganic, natural aerosols (sea-salt, mineral dust, glacial flour) and contributions of anthropogenic components (fly ash, dust from steel production and processing, etc.) contain iron that can be dissolved as FeIII in saline media. This study investigates photochemical processes in clouds and aerosols producing gas-phase Cl as a function of salt- and gas-phase composition employing a simulation chamber. Atomic Cl may contribute to the oxidative capacity of the troposphere, and our findings imply local sources. Abstract Artificial sea-salt aerosol, containing FeIII at various compositions, was investigated in a simulation chamber (made of Teflon) for the influence of pH and of the tropospheric trace gases NO2, O3 and SO2 on the photochemical activation of chloride. Atomic chlorine (Cl) was detected in the gas phase and quantified by the radical clock technique. Dilute brines with known FeIII content were nebulised until the relative humidity reached 70–90%. The resulting droplets (most abundant particle diameter: 0.35–0.46µm, initial surface area: up to 3×10–2cm2cm–3) were irradiated with simulated sunlight, and the consumption of a test mixture of hydrocarbons was evaluated for Cl, Br and OH. The initial rate of atomic Cl production per aerosol surface increased with FeIII and was ~1.9×1018 atoms cm–2s–1atCl–/FeIII=13. The presence of NO2 (~20 ppb) increased it to ~7×1018 atoms cm–2s–1, the presence of O3 (630 ppb) to ~9×1018 atoms cm–2s–1 and the presence of SO2 at 20 and 200 ppb inhibited the release slightly to ~1.7 and ~1.1×1018 atoms cm–2s–1. The observed production of atomic Cl is discussed with respect to pH and speciation of the photolabile aqueous FeIII complexes.

Metastable and stable pitting events at zinc passive layer in alkaline solutions

The electrochemical behavior of Zn in 0.5 M NaOH solutions containing various concentrations (0.01–0.1 M) of ClO3 − or ClO4 − anions was studied with potentiodynamic anodic polarization and chronoamperometry techniques. Microstructural and topographical characterization of the pitted surfaces was carried out by ex situ scanning electron microscopy and atomic force microscopy examinations. Addition of either ClO3 − or ClO4 − stimulated general corrosion and ruptured the passive layer (stable pitting), with ClO3 − being more aggressive than ClO4 −. Metastable pitting events appear as current oscillations (spikes) at potentials close to the pitting potential when Cl− ions are produced by cathodic reduction of ClO3 − and ClO4 − before passive layer growth. Current–time measurements are performed at fixed potential after production of Cl− ions and show that the rate of metastable pitting and the intensity of current spikes increase with the potential and the concentration of aggressive anions. Concepts of thin film growth are applied to the passive layer formation in order to explain those results. Metastable events are related to the presence of defects in the passive layer because their frequency and intensity are enhanced in conditions that favor defect formation and roughening in growing films, while stable pitting typically occurs at regions of high metal disorder.

Gibberellins are involved but not sufficient to trigger a shift between chasmogamous-cleistogamous flower types in Viola pubescens1

Abstract At least 50 angiosperm families have plants that produce both chasmogamous flowers and cleistogamous flowers. Various environmental and physiological factors, including the plant growth regulators gibberellins (GAs), have been reported to influence the flower types. Here, the relationship between GAs and flower production was studied for the first time in Viola, a genus famous for the large number of species with the mixed breeding system. Orthologs of genes for GA20 oxidase (VGA20ox) and GA3 oxidase (VGA3ox) were identified by reverse transcription polymerase chain reaction (RT-PCR) from a widespread North American species, Viola pubescens. Semi-quantitative RT-PCR indicated that both genes had increased expression in chasmogamous flowers as compared to cleistogamous flowers, supporting a role for GA in the differential production of flower type. However, the application of exogenous GA3 (the most common commercially available GA) to V. pubescens failed to induce a conversion of production of cl...

Mechanochemical destruction of mirex co-ground with iron and quartz in a planetary ball mill

Mechanochemical destruction (MCD) has been recognized as a promising non-combustion technology for the disposal of obsolete pesticides belonging to the persistent organic pollutants (POPs). Mirex, a termiticide ever used for many years in China, was ball milled in the presence of various reagent(s) in a planetary ball mill at room temperature to investigate the destruction efficiency. The ground samples were characterized and analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, gas chromatography (GC), and ion chromatography (Martins, Bicego et al.). Under the same conditions of mill rotary rate and charge ratio, the mixture of iron powder and quartz sand (Fe/SiO2) was found best in promoting the mirex destruction. Mirex was completed destroyed after 2h grinding at a charge ratio of 36:1 (reagent/mirex, m/m) and a mill rotation speed of 550rpm. No organic compound was detected by GC/μECD screening. The yield of water-soluble chlorine determined by ion chromatography (Martins, Bicego et al.) in the final residue accounted for 90.7% of chlorine in the original mirex, which indicated a nearly complete dechlorination. Signals of both graphite and amorphous carbon were found in the Raman spectra of the co-ground powder samples. With the main final degradation products of water soluble Cl and carbon, the mechanism of the mechanochemical destruction approach should be dechlorination followed by the carbonization.

Gaussian Binning of the Vibrational Distributions for the Cl + CH4(v4/2 = 0, 1) → H + CH3Cl(n1n2n3n4n5n6) Reactions

We test several binning techniques to obtain mode-specific final-state distributions for polyatomic reactions. Normal mode analysis is done after an exact transformation to the Eckart frame. Standard histogram binning (HB) and three different variants of the energy-based Gaussian binning (1GB) are employed to obtain the probabilities of the vibrational states. We consider the two major issues of the polyatomic quasiclassical product analysis, i.e., (1) rounding the classical action to the nearest integer can result in unphysical states and (2) the normal-mode analysis can break down for highly distorted geometries. We show that 1GB can handle issue 1 when the total vibrational energy is evaluated in the normal mode space using the harmonic approximation and both issues 1 and 2 can be solved when the total vibrational energy is calculated exactly in the Cartesian space. We found that anharmonicity in the quantized energy levels does not have a significant effect on the final-state distributions. Quasiclassical trajectory calculations are performed for the reactant ground-state and bending-excited Cl((2)P(3/2)) + CH(4)(v(4/2) = 0, 1) → H + CH(3)Cl reactions using an ab initio potential energy surface. The product analysis techniques are successfully applied to the CH(3)Cl product molecules and some qualitative features of the results are discussed.

Reactions between chlorine atom and acetylene in solid para-hydrogen: Infrared spectrum of the 1-chloroethyl radical

We applied infrared matrix isolation spectroscopy to investigate the reactions between Cl atom and acetylene (C₂H₂) in a para-hydrogen (p-H₂) matrix at 3.2 K; Cl was produced via photodissociation at 365 nm of matrix-isolated Cl₂ in situ. The 1-chloroethyl radical (·CHClCH₃) and chloroethene (C₂H₃Cl) are identified as the main products of the reaction Cl + C₂H₂ in solid p-H₂. IR absorption lines at 738.2, 1027.6, 1283.4, 1377.1, 1426.6, 1442.6, and 2861.2 cm⁻¹ are assigned to the 1-chloroethyl radical. For the reaction of Cl + C₂D₂, lines due to the ·CDClCH₂D radical and trans-CHDCDCl are observed; the former likely has a syn-conformation. These assignments are based on comparison of observed vibrational wavenumbers and ¹³C- and D-isotopic shifts with those predicted with the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ methods. Our observation indicates that the primary addition product of Cl + C₂H₂, 2-chlorovinyl (·CHCHCl) reacts readily with a neighboring p-H2 molecule to form ·CHClCH₃ and C₂H₃Cl. Observation of ·CDClCH₂D and trans-CHDCDCl from Cl + C₂D₂ further supports this conclusion. Although the reactivity of p-H₂ appears to be a disadvantage for making highly reactive free radicals in solid p-H₂, the formation of 1-chloroethyl radical indicates that this secondary reaction might be advantageous in producing radicals that are difficult to prepare from simple photolysis or bimolecular reactions in situ.

Characterisation of Cl‐ transporter and channels in experimentally induced myopic chick eyes

Background: Experimental evidence has shown that myopic and hyperopic optical defocus induces thickening and thinning of the choroids, respectively, moving the retina forward and backward toward the plane of focus; however, the underlying mechanism of this phenomenon remains elusive. It has been hypothesised that the change in choroidal thickness might be elicited by the alteration of ion and fluid transport across the retinal pigment epithelium (RPE). Therefore, the aims of the present study were to determine the content of specific Cl‐ transporter/channel mRNA and proteins in chick RPE in a normal, untreated state and in lens‐induced myopia.Methods: Thirty‐five White Leghorn chicks were used. Lens‐induced myopia was achieved by securing a ‐10 D lens in one eye, while the control eye was mounted with a plano lens. The mRNA and protein expression of the targeted Cl‐ transporter and channels were assessed by real‐time polymerase chain reaction and western blot, respectively.Results: Our results showed that the gene and protein products of several Cl‐ transporter and channels including NKCC, CFTR, ClC‐2, ClC‐5, ClC‐7 and CLCA were expressed in young chick RPE. After one day of ‐10 D lens wear, in addition to the myopic shift in refraction and choroidal thinning, there was a parallel reduction in content of some mRNAs and proteins (for example, NKCC) in the myopic eye compared with the fellow eye. Spontaneous recovery of these mRNAs and proteins to control levels was demonstrated after four days of treatment.Conclusion: The relative reduction of Cl‐ transporter and channel expression in the myopic eye might cause a decrease in ion and fluid transport across the RPE, leading to a thinning of the choroid and potentially accelerating axial elongation. Understanding of the identity of the Cl‐ transport machinery used in developing lens‐induced myopia might facilitate development of novel approaches for controlling myopic progression by influencing fluid transport by the RPE.

Ab initio molecular dynamics investigations on the S N2 reactions of OH − with NH 2F and NH 2Cl

The bimolecular nucleophilic substitution (S N2) reactions of hydroxide anion (OH −) with fluoroamine (NH 2F) and chloramine (NH 2Cl) have been investigated with ab initio molecular dynamics simulations. For the S N2 reaction of OH − with NH 2F, there are two main dynamic reaction pathways after passing the [HO···NH 2···F] − barrier. The first one is that the [HO···NH 2···F] − transition state directly dissociates to the products of F − and NH 2OH without involving any dynamic intermediate complex, and on the contrary, the other one involves the dynamic hydrogen bond F −···H−NH−OH and/or F −···H−O−NH 2 intermediate complexes. As to the S N2 reaction of OH − with NH 2Cl, there is only one dominant dynamic reaction pathway, which leads to the products of Cl − and NH 2OH directly. According to our calculations, the statistical theories including the Rice–Ramsperger–Kassel–Marcus (RRKM) theory and transition state (TS) theory cannot be utilized to model the reaction kinetics for these two S N2 reactions.

Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C–Cl bond photofission in chloroacetone at 193 nm

We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of chloroacetone at 193 nm: C-Cl bond photofission yielding CH(3)C(O)CH(2) radicals, C-C bond photofission yielding CH(3)CO and CH(2)Cl products, and C-CH(3) bond photofission resulting in CH(3) and C(O)CH(2)Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C-Cl bond photofission is followed by the dissociation of the vibrationally excited CH(3)C(O)CH(2) radicals to CH(3) + COCH(2). Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH(3) + C(O)CH(2)Cl photofission channel. We find that about 89% of the chloroacetone molecules undergo C-Cl bond photofission to yield CH(3)C(O)CH(2) and Cl products; approximately 8% result in C-C bond photofission to yield CH(3)CO and CH(2)Cl products, and the remaining 2.6% undergo C-CH(3) bond photofission to yield CH(3) and C(O)CH(2)Cl products.

Photodissociation dynamics of Cl 2O at 235 nm using velocity map ion imaging

We have investigated the photodissociation dynamics of expansion-cooled Cl 2O at 235 nm using photofragment velocity map ion imaging coupled with resonance-enhanced multiphoton ionization (REMPI) to measure the speed and angular distributions of the Cl( 2P 3/2) and Cl( 2P 1/2) products. We observe speed-dependent spatial anisotropy for both Cl fragments from the imaging data and attribute this to a fraction of nascent ClO, which undergoes secondary photodissociation. We have employed a Monte–Carlo forward-convolution scheme to analyze the data and obtain the speed distribution and anisotropy parameters for the ClO + Cl( 2P 3/2,1/2) channels. We find that the speed distribution of the Cl( 2P 3/2) + ClO channel is bimodal with an anisotropy parameter of 1.2 ± 0.2, whereas the speed distribution of the Cl( 2P 1/2) + ClO channel consists of a single component with an anisotropy parameter of 1.0 ± 0.2. We have determined branching ratios for Cl( 2P 3/2) + ClO and Cl( 2P 1/2) + ClO channels to be 0.97 ± 0.02:0.03 ± 0.02. Based on the translational energy distribution of Cl( 2P 3/2) + ClO channel, 28% of the parent molecule undergoes three-body dissociation.

Volcanic lightning as a source of reactive radical species in eruption plumes

Volcanic lightning has accompanied most recent major explosive eruptions and provides a source of intense thermal energy to drive the formation of reactive radical species. These radicals may have an impact upon the chemical evolution of the eruption plume and its interaction with the atmosphere. Equilibrium modeling shows that within each lightning channel &gt;1% of total N, O, and F and ∼100% of H, Cl, Br, and I may remain as radicals after quenching. The production of radicals generally increases with the quenching temperature of the gas mixture and the dilution of the eruption plume and decreases with increasing atmospheric pressure. Despite the small volume fraction of the plume directly exposed to volcanic lightning (i.e., &lt;10−4), the production of O, H, F, and NO is predicted to be quantitatively significant over the entire plume. Furthermore, these radicals may indirectly lead to the production of Br, Cl, HO2, and O3 through reactions occurring at low temperature. We suggest that volcanic lightning may promote the oxidation of magmatic gases (e.g., HBr and SO2) and result in a wide range of atmospheric impacts, including tropospheric ozone depletion, the production of fixed nitrogen species, and the formation of cloud condensation nuclei.