Gas Phase Ion Chemistry

The geothermal field of Akropotamos produces fluids at temperatures up to 90oC. The waters from wells AKR-1, AKR-3, AKR-4, AKR-5 and AKR-6 at 30 86oC and TDS of 3.1-30.7 g/l are classified as Na-Cl type. The water from well AKR-2 at 46oC with TDS of 2.15 g/l belongs to Na-HCO3Cl type. The cold and sub-thermal waters (16.4- 27oC) in the area are considered as fresh or low salinity waters (TDS: 0.31-4.34 g/l) of various mixed types. The Na-Cl geothermal waters can be divided into two categories due to two different hot aquifers: (a) Τhe first shallow aquifer contains high salinity waters (TDS: 27.4 30.7 g/l) at 30-48oC located within sands, sandstones and gravels. (b) Τhe second deeper reservoir composed of calcareous conglomerates and sandstones contains lower salinity waters (TDS: 3.1-5.08 g/l) at 83-90οC. The contribution of seawater to the chemical composition of the thermal waters in the shallow aquifer system seems to be important. With the aid of chemical geothermomometers appl...

Packed columns are an important part of the broad selection of mass and heat transfer equipment. Nowadays, the use of packed columns is increasing, which is because of its lower pressure drop, higher capacity and higher mass transfer in comparison to tray columns. The experiential tests and the hypothetical analysis display that the chemical dehumidification of air by hygroscopic salt solutions confirms the stable reduction in humidity ratio, which is appropriate for uses to air conditioning or drying processes The mass transfer factors in the pulse were found to correspond nearly to the factors that would be achieved in the distributed bubble flow regime In the present study, parameters that affect column performance, such as, fluid retention and gas-phase mass transfer coefficient in a humidification column using random packing in towers with 0.1 m and 0.2 m diameters and 1m height, were measured Air velocity was 1.32 to 3.92 m 3 per hour and liquid velocity was 10 to 70 m 3 per hour. In this research, the Nakajima model was used to calculate the effective area. Thereafter, experimental values for gas-phase mass transfer coefficients were compared to Zech, Shi, Grouff, Shulman, Billet and Ondamodels The mean relative errors of these models with the present study's experimental findings were 7%, 15%, 29%, 21%, 45% and 195%. Findings showed that by decreasing the column diameter, the gas-phase mass transfer coefficient (K g .ae) also increases Further, the obtained retention values showed that retention in the column with a 0.1 m diameter was higher than the column with a 0.2 m column.

On-road emissions of carbonyls from the current vehicle fleet of Brazil were determined in two experimental campaigns, conducted in traffic tunnels located in the Metropolitan Area of São Paulo (MASP), in southeastern Brazil. Among carbonyl species, formaldehyde and acetaldehyde were the most abundant in all sampling periods. In Brazil, heavy-duty vehicles (HDVs) run on a blend of 95% regular diesel/5% biodiesel from soy, whereas light-duty vehicles (LDVs) run on gasohol (75e80% gasoline/20e25% ethanol) or hydrous ethanol. We found that HDVs showed the highest overall carbonyl emissions, although LDVs were responsible for high emissions of acetaldehyde. In comparison with LDVs in California, which are powered by 90% gasoline/10% ethanol, LDVs in Brazil were found to emit 352% and 263% more formaldehyde and acetaldehyde.

The near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron (XP) spectra of gas-phase 2,8-bis-(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT) and triphenylphosphine oxide (TPPO) have been measured at the S and P L II,III-edge regions. The time-dependent density functional theory (TDDFT) based on the relativistic two-component zeroth-order regular approximation approach has been used to provide an assignment of the experimental spectra, giving the contribution of the spin−orbit splitting and of the molecular-field splitting to the sulfur and phosphor binding energies. Computed XP and NEXAFS spectra agree well with the experimental measurements. In going from dibenzothiophene and TPPO to PPT, the nature of the most intense S 2p and P 2p NEXAFS features are preserved; this trend suggests that the electronic and geometric behaviors of the S and P atoms in the two building block moieties are conserved in the more complex system of PPT. This work enables us to shed some light onto the structure of the P−O bond, a still highly debated topic in the chemical literature. Since the S 2p and P 2p NEXAFS intensities provide specific information on the higher-lying localized σ*(C−S) and σ*(P−O) virtual MOs, we have concluded that P 3d AOs are not involved in the formation of the P−O bond. Moreover, the results support the mechanism of negative hyperconjugation, by showing that transitions toward σ*(P−O) states occur at lower energies with respect to those toward π*(P−O) states.

An autoionization spectrum of the H2S molecule has been identified from the comparison between the Auger electrons recorded by means of high-resolution electron-beam and monochromatic Al Ea exciting sources. Due to the high energy resolution the measured kinetic energies can be used for a precise assignment. Our results support a model of a fast dissociation of the core-excited H2S* (2p) '(6al)' and (2p) '(3b2)' states into core-excited HS* (2p) '(2m) followed by autoionization decay into the HS+ radical. Vibrational structures are resolved and assigned to the X and '6 final states in the HS+ radical. No participator Auger process in H2S could be identified. However, contributions from the spectator process in H2S might be present.

We present a comprehensive review of published results from the last 30 years regarding the sources and atmospheric characteristics of particles and ozone in the Metropolitan Area of São Paulo (MASP). During the last 30 years, many efforts have been made to describe the emissions sources and to analyse the primary and secondary formation of pollutants under a process of increasing urbanisation in the metropolitan area. From the occurrence of frequent violations of air quality standards in the 1970s and 1980s (due to the uncontrolled air pollution sources) to a substantial decrease in the concentrations of the primary pollutants, many regulations have been imposed and enforced, although those concentrations do not yet conform to the World Health Organization guidelines. The greatest challenge currently faced by the São Paulo State Environmental Protection Agency and the local community is controlling secondary pollutants such as ozone and fine particles. Understanding the formation of these secondary pollutants, by experimental or modelling approaches, requires the description of the atmospheric chemical processes driven by biofuel, ethanol and biodiesel emissions. Exposure to air pollution is the cause of many injuries to human health, according to many studies performed not only in the region but also worldwide, and affects susceptible populations such as children and the elderly. The MASP is the biggest megacity in the Southern Hemisphere, and its specifics are important for other urban areas that are facing the challenge of intensive growth that puts pressure on natural resources and worsens the living conditions in urban areas. This text discusses

An autoionization spectrum of the H2S molecule has been identified from the comparison between the Auger electrons recorded by means of high-resolution electron-beam and monochromatic Al Ea exciting sources. Due to the high energy resolution the measured kinetic energies can be used for a precise assignment. Our results support a model of a fast dissociation of the core-excited H2S* (2p) '(6al)' and (2p) '(3b2)' states into core-excited HS* (2p) '(2m) followed by autoionization decay into the HS+ radical. Vibrational structures are resolved and assigned to the X and '6 final states in the HS+ radical. No participator Auger process in H2S could be identified. However, contributions from the spectator process in H2S might be present.

Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

Electron ionization (70 eV) mass spectra, double-stage (MS 2) 10 eV collision-induced dissociation (CID) production mass spectra of molecular ions and triple-stage (MS 3) sequential production mass spectra of major fragment ions are reported for the parent Nphenyl and the isomeric ortho-, meta-and para-N-chlorophenyl-and N-bromophenyl-2-aminobenzamidines. Dissociation is greatly influenced by an ortho effect that favors the loss of ortho H atoms and particularly the loss of the ortho halogen substituents. Dissociation occurs via a two-step intramolecular aromatic substitution reaction and a distonic-ion intermediate inhibits scrambling of ring hydrogens thus favoring the loss of the ortho substituents. The ortho isomers form an abundant and diagnostic [M-X] + fragment ion (X = Cl, Br) and are easily distinguished. Protonated 2-(1H-benzimidazol-2-yl)-phenylammonium ions are likely formed; they dissociate mainly by NH 3 loss upon CID and react readily with pyridine by proton transfer.

Research highlights  Emissions and concentrations in three Brazilian metropolitan areas are reviewed  In 2014, vehicular emissions contributed 34% of the total Brazilian PM2.5 emissions  Non-exhaust sources could represent 90% of the Brazilian PM emissions from 2020 onwards  Brazilian cities have relatively relaxed guidelines of PM concentration compared with WHO  Studied metropolitan areas showed up to 3-fold high concentrations above WHO guidelines

We report the unimolecular decomposition following collisional activation of protonated mono-, di- and trimethylbenzenes as a function of collision energy. The resulting energy-resolved mass spectra are then used for the quality control of high-level quantum chemical models of the respective potential energy surfaces. Distinction is made between direct dissociation products (CH4 or H2) and indirect products (alkenes), since formation of the latter requires extensive rearrangement of the molecular skeleton. Very good consistency was found between model and experiment. The models thereby provide a solid foundation for discussing the reaction mechanisms of the industrial methanol-to-hydrocarbon process. The losses of CH4, C2H4 and C3H6 from mesitylenium ions have been studied by 13C and 2H labelling and the alkene losses were found to occur via irreversible isomerisation pathways.

In order to reach a deeper insight into the reaction mechanism of the zeolite catalyzed methanol to hydrocarbons reaction (MTH), the proposed reaction intermediates, i.e., a series of multiply methyl-substituted benzenium ions has been generated in the gas phase by chemical ionization. The fragmentations of the corresponding long-lived (metastable) ions have been investigated. While expulsion of H 2 dominates for the lower homologues, elimination of methane dominates for the higher homologues, accompanied by increasing amounts CH 3. Loss of larger fragments relevant to the MTH-reaction, in particular ethene, propene and even butene, is also observed in minor amounts. This latter finding is consistent with a proposed reaction cycle in the MTH reaction known as the paring mechanism, and the feasibility of this mechanism has thus been demonstrated. The metastable gasphase ions studied here are considerably more energetic than those residing in a zeolite catalyst, but they were found to decompose with markedly higher selectivity towards alkenes as compared to those activated by collision-induced dissociation (CID).

High resolution X-ray spectroscopic studies on free SF 6 molecules and SF 6 clusters near the S 2p ionization thresholds are reported. Spectral changes occurring in clusters for the intense molecular-like S 2p 1/2,3/2 → 6a 1g-, 2t 2g-, and 4e g-resonances are examined in detail. Neither gas-to-cluster spectral shifts nor changes in peak shape are observed for the pre-edge 6a 1g-band. Significant changes in band shape and distinct gas-to-cluster shifts occur in the S 2p 1/2,3/2 → 2t 2g-and 4e g-transitions. These are found in the S 2p-ionization continua. The quasiatomic approach is used to assign the experimental results. It is shown that a convolution of asymmetric and symmetric contributions from Lorentzian and Gaussian line shapes allows us to model the spectral distribution of oscillator strength for the S 2p 1/2,3/2 → 2t 2g-, and 4e g-transitions. The asymmetry is due to trapping of the photoelectron within the finite size potential barrier. The Lorentzian contribution is found to be dominating in the line shape of the S 2p → 2t 2g-and 4e g-bands. The spectroscopic parameters of the spin-orbit components of both the 2t 2g-and 4e g-bands are extracted and their gas-to-cluster changes are analyzed. The photoelectron trapping times in free and clustered SF 6 molecules are determined. Specifically, it is shown that spectral changes in clusters reflected in core-to-valence-transitions are due to a superposition of the singly scattered photoelectron waves at the neighboring molecules with the primary and multiply scattered waves within the molecular cage.

Fragment ion yields in the C 1s f Rydberg excitation region of CO 2 were measured in the 90°and 0°d irections relative to the electric vector of the linearly polarized light. The C 1s f ns (n) 3, 4), npπ and npσ (n) 3-7), and nd (n) 3, 4) Rydberg transitions are clearly observed and show some vibrational structures. The dipole-forbidden C 1s(σ g) f 3sσ g Rydberg transition is the strongest of all the Rydberg transitions, and the ion yield in the 90°direction is dominant. This indicates that the bending vibration is predominantly coupled with the 3sσ g Rydberg state and the intensity-lending dipole-allowed state is a very strong π* resonance, only 2 eV lower than the 3sσ g state. On the other hand, in the 4sσ g Rydberg state the vibronic coupling through the antisymmetric stretching mode is strongly observed in the 0°direction. This is probably because the 4sσ g state approaches another intensity-lending state with Σ u + symmetry and goes away from the π* resonance. The angle-resolved ion-yield technique is very powerful for elucidating the vibronic coupling mechanism.

We present a theoretical and experimental study of the electronic structure of N-methyltrifluoroacetamide (FNMA) and examine the resonant Auger (RA) decay upon site-and state-specific excitation at the C 1s, N 1s, and O 1s edges. Based on the calculated energies for cationic states of 1h and 2h-1p configurations, we assign the peaks of recorded VUV photoelectron and RA spectra. Specifically, we identify the spectral features associated with participator and spectator RA decay. To aid in a deeper understanding of previous observations of limited site-specific bond breaking in FNMA, the influence of the site-specific excitation and the character of the Auger decay on the fragmentation is investigated using Auger electron ion coincidence experiments. Moreover, to investigate the potentially different capacity for selective bond cleavage of participator and spectator Auger states, we apply this technique to the spectator Auger state with the main electronic configuration of (31a) −1 (32a) −1 (34a) 1 , which is well resolved in the experimental spectrum. Finally, the influence of the molecular excess energy and the electronic character of the RA final states on fragmentation is addressed. Based on our findings, we argue that the excess energy the FNMA molecule gains upon RA decay is the dominant factor determining the fragmentation pattern.

The ion corresponding to protonated sulfurous acid, H 3 SO 3 + , has been successfully delivered into the gas phase by electrospray ionization of the solution of a suitable precursor and an in-source fragmentation process. The neutral acid is a highly elusive molecule. However, its gas-phase basicity has been ascertained by means of a kinetic study of proton-transfer reactivity. The structure of the H 3 SO 3 + sampled ion has been probed by IRMPD spectroscopy in two complementary IR frequency ranges in conjunction with density functional theory calculations and found to conform to a trihydroxosulfonium ion. The characteristic IR signatures may aid in deciphering the presence of this species in extraterrestrial atmospheres.

The effect of pulse width of Nd-YAG laser on the measurement of isotopic ratios of Li and lighter rare Q4 earths is studied using an in-house developed Laser Ionization Mass Spectrometer (LIMS) facility. The picosecond (ps) laser seems to provide better data compared to nanosecond (ns) laser and ps laser at 266 nm provides less scatter in the data compared to higher wavelengths. This LIMS method is a relatively simple method to measure the isotopic abundance to within ±1%.

Packed columns are an important part of the broad selection of mass and heat transfer equipment. Nowadays, the use of packed columns is increasing, which is because of its lower pressure drop, higher capacity and higher mass transfer in comparison to tray columns. The experiential tests and the hypothetical analysis display that the chemical dehumidification of air by hygroscopic salt solutions confirms the stable reduction in humidity ratio, which is appropriate for uses to air conditioning or drying processes The mass transfer factors in the pulse were found to correspond nearly to the factors that would be achieved in the distributed bubble flow regime In the present study, parameters that affect column performance, such as, fluid retention and gas-phase mass transfer coefficient in a humidification column using random packing in towers with 0.1 m and 0.2 m diameters and 1m height, were measured Air velocity was 1.32 to 3.92 m 3 per hour and liquid velocity was 10 to 70 m 3 per hour. In this research, the Nakajima model was used to calculate the effective area. Thereafter, experimental values for gas-phase mass transfer coefficients were compared to Zech, Shi, Grouff, Shulman, Billet and Ondamodels The mean relative errors of these models with the present study's experimental findings were 7%, 15%, 29%, 21%, 45% and 195%. Findings showed that by decreasing the column diameter, the gas-phase mass transfer coefficient (K g .ae) also increases Further, the obtained retention values showed that retention in the column with a 0.1 m diameter was higher than the column with a 0.2 m column.

Direct measurements of Ar^{+} 1s^{-1}2p^{-1}nl double-core-hole shake-up states are reported using conventional single-channel photoemission, offering a new and relatively easy means to study such species. The high-quality results yield accurate energies and lifetimes of the double-core-hole states. Their photoemission spectrum also can be likened to 1s absorption of an exotic argon ion with a 2p core vacancy, providing new information about the spectroscopy of both this unusual ionic state as well as the neutral atom.

Resonance K auger spectra of molecular oxygen are presented at photon energies corresponding to 10-t lag, 3o,( c?), and Rydberg excitations. Atomic-like Auger lines observed in the 30, (a*) decay spectrum are compared with the pure atomic 1 s+ 2p resonance Auger spectrum, and evidence for very fast neutral dissociation is found. The energy shifts of "spectator" lines in the spectra measured at different excitation energies are discussed and compared with the normal 0s K Auger spectrum.

São Paulo in Brazil has relatively relaxed regulations for ambient air pollution standards and often experiences high air pollution levels due to emissions of airborne particles from local sources and long-range transport of biomass burning-impacted air masses. In order to evaluate the sources of particulate air pollution (PM) and related health risks, a year-round sampling was performed for PM<sub>2.5</sub> (≤ 2.5 μm) and PM<sub>10</sub> (≤ 10 μm) in 2014 through intensive (every day sampling in wintertime) and extensive campaigns (once a week for the whole year) with 24 h of sampling. This year was characterized to have lower average precipitation comparing to meteorological data, and high pollution episodes were observed all year round, with a significant increase of pollution level in the intensive campaign, which was performed during wintertime. Different chemical constituents, such as carbonaceous species...

Pulsed Q collision induced dissociation (PQD) was developed to facilitate detection of low-mass reporter ions from labeling reagents (e.g., iTRΑQ) in peptide quantification using an LTQ mass spectrometer (MS). Despite the large number of linear ion traps worldwide, the use and optimization of PQD for protein identification have been limited, in part due to less effective ion fragmentation relative to the collision induced dissociation (CID). PQD expands the m/z coverage of fragment ions to the lower m/z range by circumventing the typical low mass cutoff of an ion trap MS. Since database searching relies on the matching between theoretical and observed spectra, it is not clear how ion intensity and peak number might affect the outcomes of a database search. In this report, we systematically evaluated the attributes of PQD mass spectra, performed intensity optimization, and assessed the benefits of using PQD on the identification of peptides and phosphopeptides from an LTQ. Based on head-to-head comparisons between CID (higher intensity) and PQD (better m/z coverage), peptides identified using PQD generally have Xcorr scores lower than those using CID. Such score differences were considerably diminished by the use of 0.1% m-nitrobenzyl alcohol (m-NBA) in mobile phases. The ion intensities of both CID and PQD were adversely affected by increasing m/z of the precursor, with PQD more sensitive than CID. In addition to negating the 1/3 rule, PQD enhances direct bond cleavage and generates patterns of fragment ions different from those of CID, particularly for peptides with a labile functional group (e.g., phosphopeptides). The higher energy fragmentation pathway of PQD on peptide fragmentation was further compared to those of CID and the quadrupole-type activation in parallel experiments.

The extent and effects of sequence scrambling in peptide ions during tandem mass spectrometry (MS/MS) have been examined using tryptic peptides from model proteins. Sequencescrambled b ions appeared in about 35% of 43 tryptic peptides examined under MS/MS conditions. In general, these ions had relatively low abundances with averages of 8% and 16%, depending on the instrumentation used. A few tryptic peptides gave abundant scrambled b ions in MS/MS. However, peptide and protein identifications under proteomic conditions with Mascot were not affected, even for these peptides wherein scrambling was prominent. From the 43 tryptic peptides that have been investigated, the conclusion is that sequence scrambling is unlikely to impact negatively on the accuracy of automated peptide and protein identifications in proteomics.

Resonant photoionization of OCS at the sulfur 2p 3/2 → 4 * resonance is observed. The spectra show three satellite structures between B (2) and C (2) valence-ionized states. Based on ab initio theoretical calculations, these satellites are assigned to 4 , 2 , and 2 shake-up-like satellites with three open shells, where the shake-up electron occupies the 4 * orbital. The transition to the spin-forbidden 4 state arises from strong singlet-triplet mixing via the spin-orbit coupling in the intermediate sulfur 2p-4 * excited state. In order to understand the observed satellite intensities, matrix elements for the Auger-like two-electron process from the intermediate sulfur 2p→ 4 * excited states to the final valence-ionized states are analytically derived.

Ar 2p photoabsorption spectra for Ar solid and Ar mixture with Kr, Xe and N 2 have been measured in order to study Ar 2p excited states in solid phase. Based on difference between partial electron yield and fluorescence yield spectra for solid Ar, Ar 2p 3/2-4s and 2p 3/2-4p excitations on surface are identified. For Ar:Kr and Ar:Xe mixtures, all bands move to lower energy as the Ar concentration decreases. Compared with solid Ar, Ar:N 2 mixtures show small red shift for the Ar 2p 3/2-4s excitation and blue shift for broad bands originating from Ar 2p-nd excitations. The spectral differences between the mixtures are discussed in terms of the polarization stabilization of the ionization threshold and the exchange repulsion of the Rydberg electron by the valence electrons of the neighboring atoms/molecules.

The X-ray photoelectron spcctn of the Na and Mg atoms xc thcoreticdlg studied wlrh an ab mitlo Cl cdcul~~ion. Ills shtikcup cnerw and infcnsity ukulalcd for Na are m good qrecmunt with c\pcrimcnt, whereas .I slgnifiwnt disqrccment is found for hlg. The satelhte obscrwd (II 6.1 eV from the hlg Is pcf 1s atlnbuled to .m extrinsic origm.

Pulsed Q collision induced dissociation (PQD) was developed to facilitate detection of low-mass reporter ions from labeling reagents (e.g., iTRΑQ) in peptide quantification using an LTQ mass spectrometer (MS). Despite the large number of linear ion traps worldwide, the use and optimization of PQD for protein identification have been limited, in part due to less effective ion fragmentation relative to the collision induced dissociation (CID). PQD expands the m/z coverage of fragment ions to the lower m/z range by circumventing the typical low mass cutoff of an ion trap MS. Since database searching relies on the matching between theoretical and observed spectra, it is not clear how ion intensity and peak number might affect the outcomes of a database search. In this report, we systematically evaluated the attributes of PQD mass spectra, performed intensity optimization, and assessed the benefits of using PQD on the identification of peptides and phosphopeptides from an LTQ. Based on head-to-head comparisons between CID (higher intensity) and PQD (better m/z coverage), peptides identified using PQD generally have Xcorr scores lower than those using CID. Such score differences were considerably diminished by the use of 0.1% m-nitrobenzyl alcohol (m-NBA) in mobile phases. The ion intensities of both CID and PQD were adversely affected by increasing m/z of the precursor, with PQD more sensitive than CID. In addition to negating the 1/3 rule, PQD enhances direct bond cleavage and generates patterns of fragment ions different from those of CID, particularly for peptides with a labile functional group (e.g., phosphopeptides). The higher energy fragmentation pathway of PQD on peptide fragmentation was further compared to those of CID and the quadrupole-type activation in parallel experiments.

Pulsed Q collision induced dissociation (PQD) was developed to facilitate detection of low-mass reporter ions from labeling reagents (e.g., iTRΑQ) in peptide quantification using an LTQ mass spectrometer (MS). Despite the large number of linear ion traps worldwide, the use and optimization of PQD for protein identification have been limited, in part due to less effective ion fragmentation relative to the collision induced dissociation (CID). PQD expands the m/z coverage of fragment ions to the lower m/z range by circumventing the typical low mass cutoff of an ion trap MS. Since database searching relies on the matching between theoretical and observed spectra, it is not clear how ion intensity and peak number might affect the outcomes of a database search. In this report, we systematically evaluated the attributes of PQD mass spectra, performed intensity optimization, and assessed the benefits of using PQD on the identification of peptides and phosphopeptides from an LTQ. Based on head-to-head comparisons between CID (higher intensity) and PQD (better m/z coverage), peptides identified using PQD generally have Xcorr scores lower than those using CID. Such score differences were considerably diminished by the use of 0.1% m-nitrobenzyl alcohol (m-NBA) in mobile phases. The ion intensities of both CID and PQD were adversely affected by increasing m/z of the precursor, with PQD more sensitive than CID. In addition to negating the 1/3 rule, PQD enhances direct bond cleavage and generates patterns of fragment ions different from those of CID, particularly for peptides with a labile functional group (e.g., phosphopeptides). The higher energy fragmentation pathway of PQD on peptide fragmentation was further compared to those of CID and the quadrupole-type activation in parallel experiments.

Argon L 2,3-M 2,3 M 2,3 Auger-electron spectra were measured in coincidence with K␣ fluorescent x rays in studies of K-shell vacancy decays at several photon energies above the K threshold and on the 1s→4 p resonance. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations, which include shake-up transitions in the resonant case. Small energy shifts of the coincident electron spectra are attributed to postcollision interaction with 1s photoelectrons. ͓S1050-2947͑97͒09006-9͔

Angle-resolved ion-yield spectra are reported for the C1s ™ Rydberg excitations of linear acetylene C H in comparison 2 2 with N and CO. The 3s U valence state is observed in the 3ss Rydberg region with no mixing. The 3ps state is found in 2 u g u the same region as the C1ss ™ 3pp state, which shows only totally symmetric vibrations. This is the first to observe that g u the Rydberg state in C H keeps gerade and ungerade symmetries without vibronic coupling through antisymmetric 2 2 stretching vibrations related to core-hole localization. On the other hand, the lowest 1p U valence state induces vibronic g coupling through bending vibrations in the 3s U and 3ss states.

Packed columns are an important part of the broad selection of mass and heat transfer equipment. Nowadays, the use of packed columns is increasing, which is because of its lower pressure drop, higher capacity and higher mass transfer in comparison to tray columns. The experiential tests and the hypothetical analysis display that the chemical dehumidification of air by hygroscopic salt solutions confirms the stable reduction in humidity ratio, which is appropriate for uses to air conditioning or drying processes The mass transfer factors in the pulse were found to correspond nearly to the factors that would be achieved in the distributed bubble flow regime In the present study, parameters that affect column performance, such as, fluid retention and gas-phase mass transfer coefficient in a humidification column using random packing in towers with 0.1 m and 0.2 m diameters and 1m height, were measured Air velocity was 1.32 to 3.92 m3 per hour and liquid velocity was 10 to 70 m3 per hour. In this research, the Nakajima model was used to calculate the effective area. Thereafter, experimental values for gas-phase mass transfer coefficients were compared to Zech, Shi, Grouff, Shulman, Billet and Ondamodels The mean relative errors of these models with the present study’s experimental findings were 7%, 15%, 29%, 21%, 45% and 195%. Findings showed that by decreasing the column diameter, the gas-phase mass transfer coefficient (Kg.ae) also increases Further, the obtained retention values showed that retention in the column with a 0.1 m diameter was higher than the column with a 0.2 m column.

The notable increase in biofuel usage by the road transportation sector in Brazil during recent years has significantly altered the vehicular fuel composition. Consequently, many uncertainties are currently found in particulate matter vehicular emission profiles. In an effort to better characterise the emitted particulate matter, measurements of aerosol physical and chemical properties were undertaken inside two tunnels located in the São Paulo Metropolitan Area (SPMA). The tunnels show very distinct fleet profiles: in the Jânio Quadros (JQ) tunnel, the vast majority of the circulating fleet are light duty vehicles (LDVs), fuelled on average with the same amount of ethanol as gasoline. In the Rodoanel (RA) tunnel, the particulate emission is dominated by heavy duty vehicles (HDVs) fuelled with diesel (5 % biodiesel). In the JQ tunnel, PM 2.5 concentration was on average 52 µg m −3 , with the largest contribution of organic mass (OM, 42 %), followed by elemental carbon (EC, 17 %) and crustal elements (13 %). Sulphate accounted for 7 % of PM 2.5 and the sum of other trace elements was 10 %. In the RA tunnel, PM 2.5 was on average 233 µg m −3 , mostly composed of EC (52 %) and OM (39 %). Sulphate, crustal and the trace elements showed a minor contribution with 5 %, 1 %, and 1 %, respectively. The average OC : EC ratio in the JQ tunnel was 1.59 ± 0.09, indicating an important contribution of EC despite the high ethanol fraction in the fuel composition. In the RA tunnel, the OC : EC ratio was 0.49 ± 0.12, consistent with previous measurements of diesel-fuelled HDVs. Besides bulk car-bonaceous aerosol measurement, polycyclic aromatic hydrocarbons (PAHs) were quantified. The sum of the PAHs concentration was 56 ± 5 ng m −3 and 45 ± 9 ng m −3 in the RA and JQ tunnel, respectively. In the JQ tunnel, benzo(a)pyrene (BaP) ranged from 0.9 to 6.7 ng m −3 (0.02-0. 1 ‰ of PM 2.5 ) whereas in the RA tunnel BaP ranged from 0.9 to 4.9 ng m −3 (0.004-0. 02 ‰ of PM 2.5 ), indicating an important relative contribution of LDVs emission to atmospheric BaP.

Ammonia is a key alkaline species, playing an important role by neutralizing atmospheric acidity and inorganic secondary aerosol production. On the other hand, the NH3/NH4+ increases the acidity and eutrophication in natural ecosystems, being NH3 classified as toxic atmospheric pollutant. The present study aims to give a better comprehension of the nitrogen content species distribution in fine and coarse particulate matter (PM2.5 and PM2.5–10) and to quantify ammonia vehicular emissions from an urban vehicular tunnel experiment in the metropolitan area of São Paulo (MASP). MASP is the largest megacity in South America, with over 20 million inhabitants spread over 2000 km2 of urbanized area, which faces serious environmental problems. The PM2.5 and PM2.5–10 median mass concentrations were 44.5 and 66.6 μg m−3, respectively, during weekdays. In the PM2.5, sulfate showed the highest concentration, 3.27 ± 1.76 μg m−3, followed by ammonium, 1.14 ± 0.71 μg m−3, and nitrate,
0.80 ± 0.52 μg m−3. Likewise, the dominance (30 % of total PM2.5) of solid species, mainly the ammonium salts, NH4HSO4, (NH4)2SO4, and NH4NO3, resulted from simulation of inorganic species. The ISORROPIA simulation was relevant to show the importance of environment conditions for the ammonium phase distribution (solid/aqueous),
which was solely aqueous at outside and almost entirely solid at inside tunnel. Regarding gaseous ammonia concentrations, the value measured inside the tunnel (46.5 ± 17.5 μg m−3) was 3-fold higher than that outside (15.2 ± 11.3 μg m−3). The NH3 vehicular emission factor
(EF) estimated by carbon balance for urban tunnel was 44 ± 22 mg km−1. From this EF value and considering the MASP traffic characteristics, it was possible to estimate more than 7 Gg NH3 year−1 emissions that along with NOx are likely to cause rather serious problems to natural ecosystems in the region.

Protein phosphorylation underlies numerous cellular signaling processes. Since a reliable prediction of phosphorylation site(s) based on a consensus amino acid sequence is rather difficult to date, determination of phosphorylation site(s) in phosphoproteins is a crucial step toward the understanding of their function at the molecular level. A conventional protocol for the determination of phosphorylation sites utilizes radioactive labeling of a phosphoprotein by 32 P and purification of digested peptides carrying radioactivity, followed by Edman degradation. This method is not only tedious, but also indirect because the evidence will be based on disappearance of a phenylthiohydantoin signal from the degradation cycle where the 32 P radioactivity is eluted. Several methodologies have been developed to determine the phosphorylation sites directly by using mass spectrometry. These include collision-induced dissociation (CID) and post-source decay (PSD), both of which tend to produce fragment ions less efficiently as the number of residues exceeds 20. Moreover, in both decay processes, there is a tendency for the phosphate group to be removed during the breakdown of the main peptide chain. We report a method that allows direct observation of phosphorylated peptide fragments of phosphopeptides exceeding 20 residues by using an in-source decay fragmentation by matrix-assisted laser desorption ionization time-of-flight mass spectrometry, yielding results which are difficult or impossible to obtain by existing methods using CID or PSD.

Hartree-Fock formalism have been carried out on COa to investigate the vibrational band profile of its high resolution ESCA spectrum. This method has involved calculations of the equihbrium geometries and the harmonic force constants, for the symmetris and the anti-symmetric vibrational modes, of the ground and the core hole state species. It is shown that the excitation of the anti-symmetric vibrational mode is responsible for the high value of the FWHM pertaining to the Or, peak. Binding and relaxation energies have been computed for the core and all the valence electrons and the values of the relaxation energies for the latter have been compared with their localization characteristics. Tnble I D.T. Clatk, .I. Miller/Core and valence ionized stares of CO, Calculated core bmding (in eV) and relaxation energies (in ev) for CO2 a) and CO a) Basis set Model b) CO, co Cl,

Electron energy-loss spectroscopy (EELS) at impact energies of 2.5-3 keV has been used to obtain the electron excitation spectra for the N 1s (K-shell), F 1s (K-shell) and valence shell regions of NFs. The inner shell spectra were recorded using small angle scattering (61') while the valence shell spectrum was obtained at zero degree scattering angle. The inner shell excitation spectra show a strongly enhanced 1s + U* type transition and continuum features which are typical for molecules with highly electronegative ligands. One of the peaks in an earlier published photoabsorption study of the N 1s region has been shown to be due to a Nz impurity. The valence shell electron energy-loss spectrum shows a number of transitions which are considered to be mainly due to valence-valence type transitions, with also some evidence of Rydberg structure.

High-resolution normal Auger-electron spectra of carbonyl sulfide subsequent to S 2p −1 photoionization at photon energies of 200, 220, and 240 eV are reported along with corresponding photoelectron spectra. In addition, theoretical results are presented that take the core-hole orientation of the various spin-orbit-split and molecular-field-split S 2p −1 states into account. Auger transitions to eight metastable dicationic final states are observed and assigned on the basis of the theoretical results. From Franck-Condon analysis, assuming Morse potentials along the normal coordinates for seven of the observed quasi-stable dicationic final states, information on the potential-energy surfaces is derived and compared with theoretical results from the literature.

Fluorescence spectra have been recorded in the wavelength region 300 nm ≤ λ(fluo) ≤ 500 nm after resonant 2p → 3d excitation of atomic Ar using monochromatic synchrotron light. The radiative emission is characterized by strong transitions from Ar + 3p 4 ( 1 S, 1 D, 3 P) n ionic states. It is mainly assigned to processes of the type 3p 4 4d → 3p 4 4p and 3p 4 4p → 3p 4 4s. In addition, we have analyzed the degree of polarization of the fluorescence lines and we have determined the alignment of the Ar + ions, which are produced after the resonant Auger decay. In comparison to investigations based on photoelectron spectroscopy, the spectral analysis of the fluorescence provides complementary information about the electronic relaxation during the resonant Auger process and, in particular, it allows one to examine directly the remaining ion.

The fragmentation of peptides containing quaternary ammonium group, but lacking easily mobilizable protons, was examined with the aid of deuteriumlabeled analogs and quantum-chemical modeling. The fragmentation of oligoproline containing quaternary ammonium group involves the mobilization of hydrogens localized at αand γor δ-carbon atoms in the pyrrolidine ring of proline. The study of the dissociation pattern highlights the unusual proline residue behavior during MS/MS experiments of peptides.

Ultrafast dissociation of the HCl and HBr molecules excited respectively to the 2p 3/2 → * and 3d 5/2 → * resonances are studied with high resolution photoelectron spectroscopy. Sharp vibrational molecular lines and broad atomic lines are observed. The analysis of the profile of the atomic lines gives access to the lifetimes of the inner shell 2p 3/2 hole in the Cl* (2p 3/2 ) −1 3s 2 3p 6 configuration, and the inner shell 3d 5/2 hole in the Br* (3d 5/2 ) −1 4s 2 4p 6 configuration.

We show the first evidence of dissociation during resonant inelastic soft X-ray scattering. Carbon and oxygen K-shell and sulfur L-shell resonant and non-resonant X-ray emission spectra were measured using monochromatic synchrotron radiation for excitation and ionization. After sulfur, L 2,3 -> π * , σ * excitation, atomic lines are observed in the emission spectra as a consequence of competition between de-excitation and dissociation. In contrast the carbon and oxygen spectra show weaker line shape variations and no atomic lines. The spectra are compared to results from ab initio calculations and the discussion of the dissociation paths is based on calculated potential energy surfaces and atomic transition energies.