Search

Jakarta Greater Area (JGA) has encountered recurrent challenges of air pollution, notably, high ozone levels. We investigate the trends of surface ozone (O3) changes from the air quality monitoring stations and resolve the contribution of meteorological drivers in urban Jakarta (2010–2019) and rural Bogor sites (2017–2019) using stepwise Multi Linear Regression. During 10 years of measurement, 41% of 1-h O3 concentrations exceeded Indonesia' s national threshold in Jakarta. In Bogor, 0.1% surpassed the threshold during 3 years of available data records. The monthly average of maximum daily 8-h average (MDA8) O3 anomalies exhibited a downward trend at Jakarta sites while increasing at the rural site of Bogor. Meteorological and anthropogenic drivers contribute 30% and 70%, respectively, to the interannual O3 anomalies in Jakarta. Ozone formation sensitivity with satellite demonstrates that a slight decrease in NO2 and an increase in HCHO contributed to declining O3 in Jakarta with 10 years average of HCHO to NO2 ratio (FNR) of 3.7. Conversely, O3 increases in rural areas with a higher FNR of 4.4, likely due to the contribution from the natural emission of O3 precursors and the influence of meteorological factors that magnify the concentration. [ABSTRACT FROM AUTHOR]

Photodissociation of iodine monochloride has been investigated at 235–248 nm by studying Doppler profiles of (2+1) resonance enhanced multiphoton ionization spectra of fragment chlorine atoms and two-photon laser induced fluorescence spectra of iodine atoms. At 235.3–237.8 nm, a measured branching ratio of [Cl*(2P1/2)]/[Cl(2P3/2)] is 0.68±0.10. At 248 nm, the [I*(2P1/2)]/[I(2P3/2)] ratio is 0.71±0.27. From the measured Doppler profiles and the ab initio calculation, the photoprepared states leading to Cl and Cl* production are assigned to the 3Π0+ (and possibly 3∑-0+) and the 1Π1 states, respectively. Nonadiabatic couplings between the potential curves have been discussed. [ABSTRACT FROM AUTHOR]

The reactions O(1D)+HCl→OH+Cl (1a) and OCl+H (1b), O(1D)+DCl→OD+Cl (2a) and OCl+D (2b), and O(1D)+Cl2→OCl+Cl (3) are studied at an average collision energy of 7.6, 7.7, and 8.8 kcal/mol for (1), (2), and (3), respectively. H, D, and Cl atoms are detected by the resonance-enhanced multiphoton ionization technique. The average kinetic energies released to the products are estimated from Doppler profile measurements of the product atoms. The relative yields [OCl+H]/[OH+Cl] and [OCl+D]/[OD+Cl] are directly measured, and a strong isotope effect (H/D) on the relative yields is found. The fine-structure branding ratios [Cl(2P1/2]/[Cl(2P3/2)] of the reaction products are also measured. The results suggest that nonadiabatic couplings take place at the exit channels of the reactions (1a) and (2a), while the reaction (3) is totally adiabatic. [ABSTRACT FROM AUTHOR]

The H, D, and Cl atoms from the photodissociation of HCl and DCl at 157 and 193 nm were detected by laser-induced fluorescence (LIF) in the vacuum ultraviolet region. The Doppler profiles of the H and D resonance lines at 121.6 nm in the LIF spectra indicate that the absorption of HCl and DCl at 157 nm is a mixture of perpendicular and parallel transition (A 1Π, a 3Π0+←X 1Σ+), while that at 193 nm results almost solely from the A 1Π←X 1Σ+ transition. The fine-structure branching ratios, are measured for the chlorine atom by LIF. Combined with the previous results, the branching ratios [Cl*(2P1/2)]/[Cl(2P3/2)] are 0.81±0.09 at 157 nm, 0.50±0.05 at 193 nm for HCl, and 0.23±0.05 at 193 nm for DCl. These results suggest that the nonadiabatic couplings during the breakup of HCl (DCl) in the excited states play an important role in determination of the fine-structure branching ratios. [ABSTRACT FROM AUTHOR]

Doppler profiles of chlorine and hydrogen atomic fragments produced in the photodissociation of mono- and dichloroethylenes at 193 nm have been measured in a pump-and-probe experiment using 2+1 resonance-enhanced multiphoton ionization. In a second experiment, the angular distributions of the Cl fragments produced from chloroethylenes at 235 and 238 nm were measured using a perfect-focusing mass spectrometer. In a third experiment, we measured the power dependence of the relative yields of H, Cl, HCl, and HCl+ produced from vinyl chloride at 193 nm. For Cl detachment, two primary processes have been confirmed. One produces an isotropic angular distribution of photofragments, while the other produces an anisotropic distribution. For H atom detachment, an isotropic angular distribution and a Boltzmann velocity distribution were found. The ratio of yields of the Cl and H fragments was found to be 4±1 for CH2CCl2 and higher than 10 for t-CHClCHCl and CCl2CClH. The H, Cl, and HCl yields were found to be first order in laser intensity, while the HCl+ yield was found to be third order. Saturation measurements of the ion yield indicate that the latter results from a 1+1+1 resonance-enhanced process involving a bound state of the parent molecule. This intermediate state may also be responsible for producing the statistical component of the Cl atom product. [ABSTRACT FROM AUTHOR]

Photofragment chlorine atoms in the 2Pj states from Cl2 at 266–500 nm are measured by a resonance-enhanced multiphoton ionization technique. The measured branching ratio of [Cl*(2P1/2)]/[Cl(2P3/2)] increases monotonically with dissociation wavelengths from (9.5±1.8)×10-3 at 308 nm to (4.7±0.5)×10-1 at 475 nm. At 375 nm≤λ≤475 nm, Doppler profiles of the chlorine atoms indicate adiabatic formation of two Cl(2P3/2) from the 1Π(1u) state of Cl2 and Cl(2P3/2)+Cl*(2P1/2) from the B 3Π(0+u) state. On the other hand, at a shorter wavelength (308 nm), Cl*(2P1/2) is generated from the 1Π(1u) state through nonadiabatic transitions during the dissociation. The relative contribution of the 1Π(1u)←X 1Σ(0+g) and B 3Π(0+u)←X 1Σ(0+g) transitions in the photoabsorption is estimated from the obtained branching ratios at 375 nm≤λ≤475 nm. [ABSTRACT FROM AUTHOR]

The Doppler profiles of the O(1D) products from the photodissociation of O2 at 157.6 nm and NO2 and N2O at 205.47 nm are detected by a resonance enhanced multiphoton ionization technique. The translation energy and angular distributions are deduced for the O(1D) atoms. Present results indicate that (a) O2 (B 3Σ-u) has a short dissociative lifetime when irradiated at 157.6 nm, (b) NO(2Π) photofragment from NO2 at 205.47 nm is mostly vibrationally excited, and (c) most of the available energy is released as kinetic energy when N2O is photodissociated at 205.47 nm. [ABSTRACT FROM AUTHOR]

Hydrocarbons (CnH2n+2, n=3, 4, and 6) and methyl halides (CH3X, X=Cl, Br, I) are photodissociated at 157 nm. The hydrogen atom photofragments are detected by a resonance-enhanced multiphoton ionization technique. The Doppler profiles of the hydrogen atoms from hydrocarbons are well represented by a Gaussian profile, while those from methyl halides by a mixture of a Gaussian and a non-Gaussian profiles. These Doppler profiles are interpreted assuming that (a) hot ethyl photofragments from hydrocarbons result in the formation of hydrogen atoms and (b) methyl halides undergo both direct and indirect photolytic scissions of the C—H bonds at 157 nm. [ABSTRACT FROM AUTHOR]

Doppler profiles of O(2p 3Pj) (j=2,1,0) produced from the photodissociation of O2 in the Herzberg I system (A3Σ+u←X3Σ-g) at 226 nm are measured with a resonance-enhanced multiphoton ionization technique. The anisotropy parameter for the angular distribution of the photofragments is found to be 1.6±0.4, in quantitative agreement with theory and indicating that the Herzberg I system borrows most of its intensity from a parallel band. The branching ratios to the j levels of O(2p 3Pj) (j=2,1,0) are found to be (2.5±0.3):1:(0.26±0.03) and are compared with the values expected for the limits of adiabatic and diabatic dissociation. [ABSTRACT FROM AUTHOR]

Alkyl chlorides (R=CH3, C2H5, C3H7, and C4H9), chloromethanes (CHnCl4-n), and chlorofluoromethanes (CFnCl4–n) are photodissociated at 157 and 193 nm. The chlorine atom photofragments are detected by a resonance enhanced multiphoton ionization technique. The branching ratios of the Cl photofragments [Cl*(3p2P1/2)]/[Cl(3p2P3/2)] are almost identical (0.23±0.03) for alkyl monochlorides at 157 and 193 nm and for CH2Cl2 and CHCl3 at 157 nm, while the ratios are rather small (0.10±0.02) for CH2Cl2 and CHCl3 at 193 nm. No discernible isotope effects on the branching ratios were observed when D atoms were substituted for H atoms in chloromethanes. For CCl4, CF3Cl, CF2Cl2, CFCl3 at 157 and 193 nm, the ratios are small (<0.05) irrespective of the number of Cl atoms in the parent molecules. The Doppler profiles of the chlorine photofragments have been obtained and it is found that (a) CF3Cl undergoes a perpendicular optical transition at 157 nm and (b) for halomethanes containing more than two Cl atoms, the Cl photofragment has a Boltzmann distribution in translational energy and an isotropic angular distribution. [ABSTRACT FROM AUTHOR]

The Doppler profiles of the hydrogen atom photofragments from the photodissociation of HCl and HBr at 157 and 243 nm are observed to determine the symmetries of the photoexcited states by using a resonance enhanced multiphoton ionization technique. The phototransitions are perpendicular for HCl at 157 nm and 193 nm and for HBr at 157 nm and 243 nm. Isotope effects on the branching ratios of [Cl*(2P1/2)]/[Cl(2P3/2)] are observed for the photodissociation of HCl and DCl at 157 and 193 nm. Our results indicate that in the photodissociation processes of HCl (A 1Π) the dynamical curve crossings during the breakup of the molecule play important roles in the determination of the branching ratio. [ABSTRACT FROM AUTHOR]

Heterogeneity in seasonal aerosol types due to different sources, local characteristics, and meteorology lead to different optical and radiative properties from one place to another. This study analyzes the long-term averages of aerosol optical and radiative properties obtained by the Aerosol Robotic Network (AERONET) version 3 at four sites in Indonesia representing fire prone areas (Palangka Raya, Pontianak, Jambi: 2012–2020), and urban-industrial (Bandung: 2009–2018). We examined the seasonal variation of aerosol optical depth (AOD), Angstrom Exponent (AE), Precipitable Water Vapor (PWV), and Single Scattering Albedo (SSA) combined with meteorological parameters at these Indonesian sites. Multiple clustering techniques from different relationships among various aerosol optical and radiative parameters was employed to further study the aerosol type in respect to different seasonality. The results exhibited a distinct seasonal pattern at all sites except Bandung, whereas AOD increased owing to forest and peat fire outbreaks during the dry season. The trend in AOD annual depicts an increase in Bandung as emission from urban/industrial increases episodically, while it depicts a decrease at the three biomass burning sites. As AOD increased, Palangka Raya, Pontianak, and Jambi exhibited wider ranges of observed AE (1.2–1.8) and high FMF (>0.8) in the dry burning period (June to October). On the other hand, Bandung has more aerosol distribution in the range of FMF values 0.6–1 and AE 1–1.6, compared with other sites, suggesting contribution of complex aerosol emission from different sources and likely due to the formation of secondary aerosol production from trace gases. Palangka Raya, Pontianak, and Jambi exhibited non-absorbing characteristics, as indicated by high SSA (>0.95), high FMF, and high EAE values (1.2–1.7) with no discrepancy in seasonal patterns, implying that biomass burning aerosols in Indonesia tend to cool the atmosphere with strong scattering rather than absorbing. At Bandung, aerosols mixed with slightly absorbing and non-absorbing aerosols owing to urban and industrial emissions. This study lays a foundation for further research on the contribution of aerosol radiative forcing to climate within the complex aerosol and cloud environments in Indonesia. • Long-term analysis of aerosol optical and radiative properties combined with the climatic condition in Indonesia. • Decreasing (increasing) tendency of interannual AOD at biomass burning (urban) sites. • Indonesia biomass burning aerosol has non-absorbing properties. • Bandung urban aerosols were mixed with slightly absorbing and non-absorbing. [ABSTRACT FROM AUTHOR]

Using mid-infrared laser absorption spectroscopy, we investigated the room-temperature pressure broadening coefficients for hydroperoxyl radicals (HO 2 ) in nitrogen and oxygen over the 1060.0–1065.5 cm −1 range of the ν 3 band. The HO 2 radicals were produced by flash photolysis of a chlorine/1,4-cyclohexadiene/oxygen mixture. The 20 measured absorption profiles were analyzed with Voigt functions. Air broadening coefficients were estimated from the nitrogen- and oxygen-broadening results and compared with previous results. We discuss the dependence of air broadening on rotational states. [ABSTRACT FROM AUTHOR]

Mid-infrared absorption spectroscopy has been applied to the detection of the hydroperoxyl (HO2) radical in pulsed laser photolysis combined with a laser absorption kinetics reactor. Transitions of the v3 vibrational band assigned to the O-O stretch mode were probed with a thermoelectrically cooled, continuous wave mid-infrared distributed feedback quantum cascade laser (QCL). The HO2 radicals were generated with the photolysis of Cl2/CH3OH/O2 mixtures at 355 nm. The absorption cross section at each pressure was determined by three methods at 1065.203 cm-1 for the F1, 131,13 ← 141,14 transition in the v3 band. From these values, the absolute absorption cross section at zero pressure was estimated. The relative line strengths of other absorptions in the feasible emitting frequency range of the QCL from 1061.17 to 1065.28 cm-1 were also measured, and agreed with values reproduced from the HITRAN database. The v3 band absorption strength was estimated from the analytically obtained absolute absorption cross section and the calculated relative intensity by spectrum simulation, to be 21.4 ± 4.2 km mol-1, which shows an agreement with results of quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Abstract: Mid-infrared absorption spectroscopy was applied to the detection of the hydroperoxyl radical (HO2) in pulsed laser photolysis combined with a laser absorption kinetics reactor. The transition of the ν 3 vibrational band assigned to the O–O stretch mode around 1065cm−1 was probed with a thermoelectrically cooled, continuous wave, mid-infrared, distributed feedback quantum cascade laser (QCL). The HO2 was generated through 355nm photolysis of Cl2/1,4-c-C6H8/O2 mixtures. The mid-infrared absorption spectrum of the HO2 radical was recorded between 1064 and 1065.5cm−1. The absorption line shapes were well represented by the Voigt profile. The nitrogen-broadening coefficients of the HO2 radical at 295K were determined for four absorption lines around 1065cm−1. Mid-infrared absorption detection using a QCL as a spectroscopic light source is a powerful method in spectroscopic and kinetics studies of the HO2 radical. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a compact, laser-based, single photon ionization time-of-flight mass spectrometer (SPI-TOF-MS) for on-line monitoring of trace organic species. To obtain the mass spectrum, we use a nearly fragmentation-free SPI technique with 10.5eV (118nm) vacuum ultraviolet laser pulses generated by frequency tripling of the third harmonic of an Nd:YAG laser. The instrument can be operated in a linear TOF-MS mode or a reflectron TOF-MS mode in the coaxial design. We designed ion optics to optimize detection sensitivity and mass resolution. For data acquisition, the instrument is controlled using LabVIEW control software. The total power requirement for the vacuum unit, control electronics unit, ion optics, and detection system is approximately 100W. We achieve a detection limit of parts per billion by volume (ppbv) for on-line trace analysis of several organic compounds. A mass resolution of 800 at about 100amu is obtained for reflectron TOF-MS mode in a 0.35m long instrument. The application of on-line monitoring of diesel engine exhaust was demonstrated. [Copyright &y& Elsevier]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Abstract: The line shape profiles of the 000–000 band of hydroperoxy radical (HO2) have been measured in the presence of nitrogen and water using laser photolysis/cw near infrared two-tone frequency modulation spectroscopy. On the basis of the theory described by Avetisov and Kauranen [Appl. Opt. 35 (1996) 4705], the absorption line shapes were well represented by the Voigt profile. The nitrogen- and water-broadening coefficients for the 7020.766cm−1 161,16←160,16 F1 line of HO2 were estimated to be 0.101±0.013 and 0.216±0.133cm−1atm−1, respectively. The large value of water-broadening coefficient suggests the long range interaction between HO2 with water. [Copyright &y& Elsevier]

Cavity ring-down spectroscopy combined with pulsed laser photolysis has been used to study the near-ultraviolet absorption spectrum (375−410 nm, 2̃2B1 ← X̃2B1 transition) of the phenoxyl radical (C6H5O•) in 10−20 Torr of nitrogen diluent at 298 K. By using a numerical fitting routine on the basis of a modeling of chemical reaction system, the absorption cross section of the phenoxyl radical was obtained, σ = (7.7 ± 2.3) × 10-18 cm2 molecule-1 (base e) at 394.4 nm. A spectrum simulation was carried out using available Franck−Condon integrals with a 400 cm-1 Lorentzian line width, which suggests a short-lived excited state. Time-dependent density functional theory (TD-UB3LYP/aug-cc-pVTZ) calculations supported the interpretation of the absorption band for the phenoxyl radical. The rate constant of the phenoxyl radicals with methyl radicals was derived, k(C6H5O + CH3) = (6.2 ± 2.6) × 10-11 cm3 molecule-1 s-1, at 298 K in 20 Torr of nitrogen diluent. [ABSTRACT FROM AUTHOR]

The Raman line widths of 16 vibron modes in RDX, β-HMX and Tetryl crystals have been measured at the temperature ranging from 3.6 to 300.0 K. The experimental line shapes were deconvoluted to extract inhomogeneous contribution to the line broadening due to probably crystal defects. The inhomogeneous line width is independent of temperature for most measured modes. The homogeneous line width is interpreted on the basis of elementary relaxation mechanisms. Three-phonon and dephasing processes are dominant relaxation processes for most of the vibrons of RDX, β-HMX and Tetryl. In particular, for Tetryl crystal, the vibrational relaxation is dominated by three-phonon down processes. For RDX and β-HMX crystals, vibrational relaxation is dominated by three-phonon down processes at lower temperature, three-phonon up or dephasing mechanisms generally contribute to the vibron dynamics while above 60 K. The lifetimes of some vibrons in the frequency range of 200–900 cm−1 in RDX, 200–1450 cm−1 in β-HMX and 200–1100 cm−1 in Tetryl crystal were calculated in term of the line widths at low temperature. The lifetimes of the measured vibrons fall in the range of 2.5–11 ps. [Copyright &y& Elsevier]

The energy transfer rates between phonons and vibrons in the “doorway region” could be the rate-determining step for impact-induced detonation of molecular crystalline explosives. To investigate the relationship between impact sensitivities and energy transfer, the overall rate of energy transfer in the doorway region is estimated on the basis of a simple theory in which the rate is proportional to a product of the number of states and the rate of population relaxation. We estimated frequencies of normal mode vibrations of PETN, β-HMX, RDX, Tetryl, TNT, FOX-7, m-DNB, ANTA, PN, NQ, NTO, and DMN by means of density functional theory calculations at the B3LYP/6-31G(d) level of theory. Normal mode vibrations of TATB were evaluated by using empirical intra-molecular potentials. The number of doorway modes in the regions of 200 to 700 cm−1 was evaluated by the direct counting method. It is found that the number of doorway modes shows a strong correlation with impact sensitivities obtained by drop hammer tests. This can be explained by the theory, if we assume that the rate of population relaxation is almost the same for all of the explosives investigated in the present work. This assumption is consistent with recent experimental measurements of energy transfer rates of explosives at low temperatures. [Copyright &y& Elsevier]

Gas-phase reactions of simple silicon hydride species underlying many types of chemical vapor deposition processes for silicon-based thin-film growth are reviewed in this paper. Mass spectrometry and laser-based spectroscopy are applied to identify gas-phase intermediates in thermal and hot-wire chemical vapor deposition processes. The mechanism of the thermal decomposition of silanes, including reactions that lead to the formation of hydrogenated silicon clusters, is examined. The gas-phase chemical kinetic mechanism in hot-wire chemical vapor deposition is proposed to explain precursor molecules for the film growth. [Copyright &y& Elsevier]

Ozone (O3) is a pollutant of concern in urban areas because of its effects on health, crops, ecosystems, and materials. Despite efforts to meet the Japanese air quality standard for O3 in the Kanto region, the attainment percentage is close to zero. Considering that O3 formation is sensitive to emissions of volatile organic compounds (VOC) and nitrogen oxides (NOx), this study evaluated a range of reductions in the emissions of both precursors using a regional air quality model (ADMER-PRO) and estimated their benefits measured as the economic change due to O3 concentration differences between scenarios. The simulation period was set during the 2016 O3 season. The results showed that O3 concentrations could be reduced using two approaches: significant reduction in VOC levels combined with minor NOx level changes or significant NOx emission reduction. Significant reduction in NOx levels was the most effective strategy for a generalized decrease in the O3 levels in the Kanto region, and the benefit analysis revealed that the most significant economic impacts could be achieved by adopting the latter approach. [ABSTRACT FROM AUTHOR]

• The enthalpies of adduct formations (EAFs) between alkyl iodides (RI) and chlorine (Cl) atoms are investigated. • The EAFs decreases when the number of alkyl substituents on the C atom bonded to I atom is increased. • The mechanism of the trend of the EAFs is suggested. The equilibrium geometries for the ground state of the adducts formed between alkyl iodides (RI) and chlorine (Cl) atoms were optimized, and the enthalpies of adduct formations (EAFs) were obtained. The EAFs decreased when the number of alkyl substituents on the C atom bonded to I atom was increased. This trend suggests that the amount of charge transferred from the electron-donating alkyl group to I Cl increases in accordance with the number of substituents, which results in the stabilization of the adduct. Charge density distribution between the Cl and H atoms was an additional mechanism to stabilize the adducts. [ABSTRACT FROM AUTHOR]

The plans to introduce next-generation hybrid and zero-emission vehicles in the market are now enacted by governments in many countries to manage both global warming and air pollution problems. There are only a few studies evaluating the effects of the next-generation vehicles on the changes in concentrations of ozone generated by the photochemical reactions between volatile organic compounds and nitrogen oxides (NOx). To evaluate these changes, we performed chemical transport modeling in the Kanto region, Japan in the summer of 2013. The results show that if the vehicles are substituted by hybrid vehicles, average ozone concentrations increase in urban areas and decrease in suburban areas due to NOx titration. Substitution with zero-emission passenger vehicles decreases the concentrations in both urban and suburban areas. Substitution with both hybrid and zero-emission passenger and heavy-duty vehicles highly increases the concentrations in urban areas. Using the model results, we also discuss the effect of ozone concentration changes on premature mortality of humans in summer. The results suggest that, in some cases the introduction of next-generation vehicles might exasperate ozone concentrations, even leading to 5 to 10 times higher premature mortality during the summer compared to that of influenza and heat stroke in Japan. [ABSTRACT FROM AUTHOR]

Presents a correction on an article about photodissociation of hydrogen chloride and hydrogen bromide.

Presents a correction on an article about fine structure branching ratios and Doppler spectroscopy of chlorine atoms from the photodissociation of alkyl chlorides and chlorofluoromethanes.

A kinetic study of the reaction of the 4‐methylphenyl radical (4‐C6H4CH3) with the oxygen molecule was conducted using experimental and theoretical approaches. The absorption spectrum for the λ = 266 nm photolysis of the 4‐C6H4CH3X (X = Cl, Br)/N2/O2 mixture was measured in the wavelength range of λ = 503‐512 nm using N2 as the buffer gas at a total pressure of 40 Torr using a cavity ring‐down spectroscopy apparatus coupled with a pulsed laser photolysis system. Based on the absorbance of the product of the 4‐C6H4CH3 + O2 reaction at λ = 504 nm, the reaction rate coefficient for the 4‐C6H4CH3 + O2 reaction was determined to be k = (1.21 ± 0.10) × 10−11 cm3 molecule−1 s−1 and k = (1.18 ± 0.21) × 10−11 cm3 molecule−1 s−1 using 4‐C6H4CH3Cl and 4‐C6H4CH3Br, respectively, as the radical precursor. And there was no pressure dependence in the total pressure range of 10‐90 Torr varying partial pressure of N2 buffer gas at T = 296 ± 5 K. The geometries, vibration frequencies, and potential energy surfaces of the reactants, major products, and transition states in the 4‐C6H4CH3 + O2 reaction were determined using the CBS‐QB3 method. The k value at the high‐pressure limit was calculated to be 1.26 × 10−11 cm3 molecule−1 s−1 using the variational transition‐state theory. The calculated value of k was consistent with the experimental value, which indicated that the 4‐C6H4CH3 + O2 reaction reaches the high‐pressure limit at 10 Torr. Therefore, the oxidation of the 4‐C6H4CH3 radical is almost 10 times faster than that of the benzyl radical, which has the same chemical formula, at the high‐pressure limit. [ABSTRACT FROM AUTHOR]

The O(2p 3Pj) (j=2, 1, and 0) fragments produced in the 157 nm photodissociation of CO2 were detected by resonance-enhanced multiphoton ionization in a molecular beam. The Doppler profiles and fine-structure branching ratios were measured for the oxygen-atom photofragment in the 3Pj states. The Doppler profiles were analyzed to give an anisotropy parameter of β=2.0±0.2 and an internal energy equivalent to 3.9±0.3 vibrational quanta of CO. The fine-structure populations were found to be 0.70±0.05, 0.16±0.03, and 0.14±0.03 (with error bars of ±σ) for j=2, 1, and 0, respectively. A mechanism is proposed in which complex on the 1B2 surface undergoes intersystem crossing to the 3B2 surface. A phase-space model with a constraint on the impact parameter is shown to be consistent with the observed energy release. The nonstatistical fine-structure population could be caused by long-range interactions on the triplet surface. In a bulb experiment, O(3P) was produced by quenching of O(1D). The fine-structure populations of the resulting O(3Pj) were 0.64±0.04, 0.25±0.04, and 0.11±0.04. This state distribution is consistent with a long-lived complex which decays to give statistical products. [ABSTRACT FROM AUTHOR]

O(2p3Pj) atoms produced from the reaction between H(1s2S) and O2(X3Σ-g) at collision energies (Ecoll) of 2.5 and 2.1 eV are detected by a resonance enhanced multiphoton ionization technique. From the Doppler profile measurements of O(3Pj), the average kinetic energy released to the products is estimated. The results suggest that the average fraction of the kinetic energy disposal at Ecoll =2.1 eV is larger than that at Ecoll =2.5 eV. The obtained branching ratios of O(3Pj) j=2, 1, and 0 at Ecoll =2.5 eV are (0.70±0.02), (0.21±0.02), and (0.09±0.02), and those at Ecoll =2.1 eV are (0.63±0.02), (0.25±0.04), and (0.12±0.02), respectively, with error bars of ±σ. The results suggest that the nonadiabatic couplings at the last stage of the reaction are important for the determination of the ratios. [ABSTRACT FROM AUTHOR]

Simultaneous measurements of on-road and in-vehicle NO and NO 2 levels, particle number concentrations (PNCs), and particles size distributions were performed while driving using a test vehicle equipped with real-time sensors. The results obtained on regional roads showed that heavy-duty vehicles in traffic seem to have a major impact on on-road air quality. Measurements on highways that included a 10 km tunnel and a 2 km uphill section of road indicated that sub-50 nm particles have different features from the other species because of their higher volatility. The other species showed quite high on-road concentrations in the tunnel. In-vehicle conditions were made similar to the on-road ones by setting the air conditioning (AC) mode to the fresh air mode. The in-vehicle NO 2 concentration in the tunnel was over 0.50 ppmV, which is almost five times higher than the 1-hour ambient air quality standard proposed by the World Health Organization (WHO). In sections other than the tunnel, the in-vehicle NO 2 concentration was almost the same as the 1-hour WHO standard. Higher on-road NO 2 /NOx ratios than those of exhaust gases and different behavior of sub-50 nm particles from other species suggested that NO 2 and sub-50 nm particles were mainly due to secondary products formed by atmospheric reactions. [ABSTRACT FROM AUTHOR]

Abstract: Direct absorption spectra of methane (12CH4 and 13CH4) at room temperature have been recorded using a 2.4-μm distributed feedback laser. Integrated cross-sections of 13CH4 were measured and compared with those listed in the HITRAN 2008 and 2012 databases, indicating that there are some discrepancies between our results and both editions of the HITRAN database. The pressure-broadening parameters of those 13CH4 lines in synthetic air were also examined experimentally. For the purpose of determining the carbon isotope ratio (13CH4/12CH4) through the spectral measurements, candidate line pairs of 12CH4 and 13CH4 within the range 4147–4154cm−1 were explored. Resultantly, the well-isolated line pair of 12CH4 at 4151.843cm−1 and 13CH4 at 4151.966cm−1 was suggested to be a candidate for determining the carbon isotope ratio of CH4 in this wavenumber region. [Copyright &y& Elsevier]

Gaseous I2formation fromthe heterogeneous reactionof gaseous ozone with aqueous iodide in the presence of aqueous ferrousion (Fe2+) was investigated by electron impact ionizationmass spectrometry. Emission of gaseous I2increased asa function of the aqueous FeCl2concentration, and themaximum I2formation with Fe2+was about 10times more than without Fe2+. This enhancement can be explainedby the OH–scavenging by Fe3+formedfrom Fe2+ozonation to produce colloidal Fe(OH)3. This mechanism was confirmed by measurements of aqueous phase productsusing a UV–vis spectrometer and an electrospray ionizationmass spectrometer. We infer that such a pH-buffering effect may playthe key role in general halogen activations. [ABSTRACT FROM AUTHOR]

Abstract: A silicone membrane sample introduction system combined with a vacuum ultraviolet single photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS) has been developed to detect trace volatile organic compounds in environmental air. The maximum enrichment factors of benzene, toluene, and chlorobenzene using the membrane introduction system relative to a direct introduction system were found to be 15.3, 11.0, and 12.1, respectively. The gas permeability of toluene through the silicone membrane was consistent with that of the manufacturer''s reported value. The gas permeabilities of the silicone membrane used in the present study were estimated for benzene and chlorobenzene by theoretical calculations using the enrichment factors. The enrichment factors of benzene, toluene, and chlorobenzene were independent of their mixing ratios at <34ppmv. The detection limits of benzene and chlorobenzene with the membrane introduction system were improved by one order of magnitude relative to direct introduction. Detection of almost sub-ppbv level of benzene and chlorobenzene was achieved in the membrane introduction VUV-SPI-TOFMS. [Copyright &y& Elsevier]

We have investigated the pressure dependence of the detection sensitivity of CO2, N2O and CH4 using wavelength modulation spectroscopy (WMS) with distributed feed-back diode lasers in the near infrared region. The spectral line shapes and the background noise of the second harmonics (2f) detection of the WMS were analyzed theoretically. We determined the optimum pressure conditions in the detection of CO2, N2O and CH4, by taking into consideration the background noise in the WMS. At the optimum total pressure for the detection of CO2, N2O and CH4, the limits of detection in the present system were determined. [ABSTRACT FROM AUTHOR]

We have investigated the pressure dependence of the detection sensitivity of CO2, N2O and CH4 using wavelength modulation spectroscopy (WMS) with distributed feed-back diode lasers in the near infrared region. The spectral line shapes and the background noise of the second harmonics (2f) detection of the WMS were analyzed theoretically. We determined the optimum pressure conditions in the detection of CO2, N2O and CH4, by taking into consideration the background noise in the WMS. At the optimum total pressure for the detection of CO2, N2O and CH4, the limits of detection in the present system were determined. [ABSTRACT FROM AUTHOR]

Abstract: Visible absorption spectra of the cyclohexadienyl radical (c-C6H7) assigned to the electronic transition have been measured using laser photolysis coupled with a cavity ring-down spectroscopic detection technique. Spectral simulation of the rotational structure of an origin band at room temperature was performed using molecular constants predicted by quantum chemical calculations. Pressure dependence of the self-reaction of the cyclohexadienyl radical was measured in the pressure range of 10–100Torr. The reaction rate coefficient of the cyclohexadienyl radical with molecular oxygen at 10Torr N2 buffer and room temperature was determined to be (5.4±0.7)×10−14 cm3 molecule−1 s−1, which is in good agreement with previous reported value measured at 760Torr. [Copyright &y& Elsevier]

Abstract: Time-resolved measurements of HO2 and OH have been conducted in 355nm photolysis of dimethyl ether/Cl2/O2 mixture at elevated temperature, using near-infrared frequency modulation spectroscopy. A part of OH was found to be produced at a timescale of several microseconds by the methoxymethyl with O2 reaction, while HO2 is formed mainly in milliseconds with the yield increasing up to 60% between 500 and 600K. It was rationalized that HO2 is not a direct product of the O2 adduct decomposition, but a secondary product through HCHO+OH reaction. Another pathway through HCO formation from the adduct is also discussed. [Copyright &y& Elsevier]

Abstract: Chemical kinetics of a novel metal CVD method (Metal Chloride Reduction CVD; MCR-CVD) has been investigated. The MCR-CVD can be applied to thin-film deposition of copper and various other metals. In the MCR-CVD process of Cu, gaseous copper chlorides produced by chlorine-assisted etching of a copper surface serves as the precursors of copper thin-film deposition. On the substrate surface, the precursor (copper chlorides) are reduced to copper by the reaction of chlorine atoms. In the present study, chemical kinetics of etching processes has been investigated. Various products of the reaction of high-temperature copper plate and chlorine molecules were detected. In the gas phase, copper chlorides exist as Cu n Cl n (n =1–5) molecules. CuCl could be detected by a laser induced fluorescence (LIF) method during the MCR-CVD process. It is found that Cl atom is not needed for the production of CuCl. CuCl is mainly produced by the reaction of Cl2 molecules with a hot copper surface. Cu n Cl n (n =3, 4) molecules were also detected in the MCR-CVD process by using an electron impact-mass spectrometry (EI-MS). [Copyright &y& Elsevier]

Solid fuels comprising low-melting-point thermoplastics (LTs) have been developed as hybrid rocket fuels. However, it is necessary to improve the regression rate of such fuels for practical application. In this study, the pyrolysis mechanism of an LT fuel in the absence of oxygen was investigated and the combustion-inhibition species among the gaseous pyrolysis products were identified. Pyrolysis–gas chromatography was used to analyze the hydrocarbon compounds produced from the pyrolysis of the LT fuel and its constituents. Detailed chemical reaction simulations were performed to dissect the pyrolysis mechanism of paraffin oil, the principal constituent of the LT fuel. The results revealed that the pyrolysis and evaporation of the fuel components yield aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), which reduces fuel combustion. Notably, the C 2 H 4 generated during paraffin pyrolysis considerably amplified the formation of aromatic hydrocarbons and PAHs, further inhibiting combustion. C 2 H 4 was also identified as one of the potential chemical species that inhibit combustion. The C 2 H 4 ratio in the fuel pyrolysis gas can be considered as an indicator for evaluating fuel compositions that enhance the fuel regression rate. • Low-melting-point thermoplastic (LT) fuel produces combustion gases through evaporation and pyrolysis of its constituents. • Pyrolysis of LT fuel produces polycyclic aromatic hydrocarbons (PAHs) that inhibit combustion after the olefin formation. • Pyrolysis product gases such as C 2 H 2 , C 2 H 4 , C 3 H 6 , and C 4 H 6 , contribute to the PAHs formation. • LT fuel's flammability can be assessed by the amount of C 2 H 4 produced during pyrolysis, a key factor in forming PAHs. [ABSTRACT FROM AUTHOR]

A time-step model was constructed to estimate the amount of evaporative emissions from vehicular diurnal breathing loss (DBL) on the basis of fuel adsorption–desorption experiments for several carbon canisters attached to seven gasoline vehicles using a chassis dynamometer. Experimental results showed that the canister's total volatile organic compound (VOC) storage ability is proportional to the canister volume, and a canister's desorption ability strongly depends on the amount of VOC trapped in the canister and the air purge flow rate of each vehicle. These properties were formulated into equations by regression analysis and used with the material balance inside the canister to propose a model for estimating emissions after carbon canister breakthrough, which are a function of a vehicle's driving and parking frequency. The model was applied to DBL experimental results derived from our previous studies to confirm its validity. Better agreement between the model and the previous experimental results was obtained when appropriate parameters were set. The proposed model is expected to contribute to estimating the VOC emission inventory for gasoline vehicles. Unlabelled Image • We measured carbon canister adsorption ability for gasoline vehicles. • Canister purge ability was measured using a chassis dynamometer. • We propose a model that estimates evaporative emissions from vehicles. • The proposed model closely replicates our previous experimental results. • Our model will contribute to estimating the VOC emission inventory. [ABSTRACT FROM AUTHOR]

The effects of Reid vapor pressure (RVP) on refueling emissions and the effects of ethanol 10% (E10) fuel on refueling and evaporative emissions were observed using six cars and seven fuels. The results indicated that refueling emissions can be reproduced by a simple theoretical model in which fuel vapor in the empty space in the tank is pushed out by the refueling process. In this model, the vapor pressures of fuels can be estimated by the Clausius–Clapeyron equation as a function of temperature. We also evaluated E10 fuel in terms of refueling and evaporative emissions, excluding the effect of contamination of ethanol in the canister. E10 fuel had no effect on the refueling emissions in cases without onboard refueling vapor recovery. E10 showed increased permeation emissions in evaporative emissions because of the high permeability of ethanol. And with E10 fuel, breakthrough emissions appeared earlier but broke through slower than normal fuel. Finally, canisters could store more fuel vapor with E10 fuel. [ABSTRACT FROM AUTHOR]

In this study, we conducted seven-day diurnal breathing loss (DBL) tests on gasoline vehicles. We propose a model based on the theory of thermodynamics that can represent the experimental results of the current and previous studies. The experiments were performed using 14 physical parameters to determine the dependence of total emissions on temperature, fuel tank fill, and fuel vapor pressure. In most cases, total emissions after an apparent breakthrough were proportional to the difference between minimum and maximum environmental temperatures during the day, fuel tank empty space, and fuel vapor pressure. Volatile organic compounds (VOCs) were measured using a Gas Chromatography Mass Spectrometer and Flame Ionization Detector (GC-MS/FID) to determine the Ozone Formation Potential (OFP) of after-breakthrough gas emitted to the atmosphere. Using the experimental results, we constructed a thermodynamic model for estimating the amount of evaporative emissions after a fully saturated canister breakthrough occurred, and a comparison between the thermodynamic model and previous models was made. Finally, the total annual evaporative emissions and OFP in Japan were determined and compared by each model. [ABSTRACT FROM AUTHOR]

A sensor for the detection of ethylene (CH) in combustion exhaust based on a mid-infrared wavelength modulation spectroscopic technique was constructed using a distributed feedback interband cascade laser (DFB-ICL) with a wavelength of 3.3 μm. The direct absorption spectrum of CH in the range of 2978.8-2982.1 cm was recorded, where the spectrum was in good agreement with the spectrum simulated using parameters from the HITRAN 2012 database. The absorption line at 2979.581 cm [2.42 × 10 cm mol cm, ν P(5)] was selected for CH detection. This frequency was chosen to minimize spectral interference from other major combustion products in the emission frequency range of the DFB-ICL. A limit of detection for CH of 96 parts per billion by volume was achieved at a signal-to-noise ratio of two under 3 kPa of pressure using 2 f wavelength modulation spectroscopy. Using the developed sensor, the ethylene concentration in the exhaust from a portable power generator was also successfully determined. [ABSTRACT FROM AUTHOR]

A compact multi-pass cell with a pair of cylindrical mirrors for sensitive detection of trace gases in emission from combustion was constructed. The cell path-length was 9.8 m and its volume was 0.13 L. Each mirror shape was a square with a side length of 25.4 mm and the mirrors were placed 100 mm apart. The cell was applied to detection of formaldehyde (HCHO), which is formed during fuel combustion and is harmful to the environment. The direct absorption spectrum in the range 2979.06–2981.2 cm −1 was recorded with a mid-infrared distributed feedback (DFB) interband cascade laser. The recorded spectrum of HCHO was in good agreement with a spectrum simulated using the HITRAN 2012 database. An absorption line at 2979.663 cm −1 (4.26 × 10 −21 cm 2 molecule −1 cm −1 , ν 5, 11 84 –10 73 ), which showed the strongest absorption in the emission frequency range of the DFB interband cascade laser, was selected for HCHO detection. We also confirmed that there were no interferences of absorption peaks of major combustion products in the selected HCHO absorption peaks. At a signal-to-noise ratio of two and 3 kPa using 2f wavelength modulation spectroscopy at less than 1 MHz bandwidth, the limit of detection for HCHO was 73 ppb by volume. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured stable carbon isotope ratios of CO2 by a laser absorption spectrometer. [•] The H2O broadening coefficients of CO2 were determined. [•] The effect of humidity on δ13C determination was examined. [•] The spectrometer keeps constant measurement conditions over 12-h periods. [ABSTRACT FROM AUTHOR]

Abstract: In situ measurements of nitrogen dioxide (NO2) concentrations were conducted at an urban site in Tokyo (35°71′N, 139°76′E), Japan during the summers of 2007–2009. A chemiluminescence instrument equipped with a molybdenum oxide converter (Mo-CL) and a laser-induced fluorescence (LIF) instrument were used simultaneously for determining the ambient NO2 concentrations. A tight linear correlation between the NO2 concentrations determined by the LIF and Mo-CL techniques was evident except for high ozone concentration periods over 50 ppbv. During the high ozone episodes, correlation plots of the NO2 concentrations between Mo-CL and LIF techniques indicated an overestimation of Mo-CL NO2. To examine in detail the systematic differences between two techniques, a thermal dissociation laser-induced fluorescence (TD-LIF) instrument was employed in the summer of 2009 to measure total peroxy nitrates (ΣPNs) and total reactive nitrogen (NO z ). We found that the ΣPNs concentrations correlated well with the discrepancies in NO2 concentrations determined by the Mo-CL and LIF techniques. This result suggests that peroxy nitrate species significantly contribute to the observed interference in the Mo-CL measurements under high O3 concentrations in our observation at the urban site in Tokyo. [Copyright &y& Elsevier]

Particle mass spectrometers of two types-a time-of-flight aerosol mass spectrometer (AMS) of Aerodyne Research Inc. and a laser desorption/ionization single particle aerosol mass spectrometer (LISPA-MS) developed at Nagoya University-were deployed to characterize aerosol particles in the Tokyo metropolitan area during the summer of 2008. Based on the ensemble measurements by AMS, equivalent mass concentration of organic aerosol, traced by mass-to-charge ratio (m/z) 44, showed a closer correlation with particulate nitrate and gas-phase odd oxygen, [O3+NO2], whereas equivalent mass concentration of organic aerosol, traced by m/z 57, did not. On a particle-by-particle basis, the relative signal peak area of various target species in the LISPA-MS spectra, which was calculated as the ion-signal fraction of the species relative to the total signal peak area summed over all the ion peaks in each spectrum, was used as a measure of the relative amount of the species. A rough qualitative agreement was obtained between the temporal variation observed in the LISPA-MS RCOO- signal and that in the AMS m/z 44, but not the AMS m/z 57, in which the LISPA-MS RCOO- signal was defined as the sum of the relative signal peak areas of 17 different negative-ion mass peaks used as markers of oxygenated organics. Analysis of the LISPA-MS spectra also showed that approximately 95% of the oxygen-containing organic particles contained nitrate, which is expected to be responsible in part for the correlation between AMS m/z 44 and AMS nitrate. [ABSTRACT FROM AUTHOR]