Measured Mass Spectra Research Articles

Nanopore ion sources deliver individual ions of amino acids and peptides directly into high vacuum

Electrospray ionization is widely used to generate vapor phase ions for analysis by mass spectrometry in proteomics research. However, only a small fraction of the analyte enters the mass spectrometer due to losses that are fundamentally linked to the use of a background gas to stimulate the generation of ions from electrosprayed droplets. Here we report a nanopore ion source that delivers ions directly into high vacuum from aqueous solutions. The ion source comprises a pulled quartz pipette with a sub-100 nm opening. Ions escape an electrified meniscus by ion evaporation and travel along collisionless trajectories to the ion detector. We measure mass spectra of 16 different amino acid ions, post-translationally modified variants of glutathione, and the peptide angiotensin II, showing that these analytes can be emitted as desolvated ions. The emitted current is composed of ions rather than charged droplets, and more than 90% of the current can be recovered in a distant collector.

Tandem Energy-Analyzer/Mass-Spectrometer Measurements of an Ionic Liquid Ion Source

Ionic liquid ion sources (ILISs) produce charged particle beams by using a strong electric field to extract and accelerate molecular ions and ion clusters from liquid propellant. The wide variety of emitted species and the fragmentation of metastable ion clusters lead to broad distributions of energy and mass among plume species. Quantifying those distributions is critical to understanding ILIS physics and ILIS performance in a particular application. Here, we use an electrostatic energy analyzer in tandem with a mass spectrometer (EA/MS) to measure mass spectra for various energy ranges in the plume of an ILIS operating with the electrospray propellant EMI-BF4. Those spectra were used to calculate energy distributions for major plume species, probed at the entrance of the EA/MS instrument. Those measurements suggest that 12% of the plume (by current fraction) is composed of species formed by ion clusters that fragment more than once prior to reaching the instrument. For the first time, we estimate the composition of the plume within the electric field of the ion source from experimental measurements. That analysis shows that at least 10% of plume current was emitted as trimers, and more than 3% was emitted as larger species.

In-situ spectral reflectance investigation of hetero-epitaxially grown β-Ga2O3 thin films on c-plane Al2O3 via MOVPE process

Metalorganic vapor-phase epitaxy of β-Ga2O3/c-plane Al2O3 heterostructures was monitored in-situ by spectral reflectance in different wavelengths. The reflectance spectrum was analysed as a function of the growth time and the incident wavelength to estimate the growth rate and the refractive index at the growth temperatures. The obtained values are validated by ex-situ methods such as secondary ion mass spectrum measurement and spectroscopic ellipsometry. A theoretical simulation of the reflectance spectrum was carried out by combining a transfer matrix method with a multilayer model, and a good agreement with the experimental results is presented.

Sequential fission and the influence of 208Pb closed shells on the dynamics of superheavy element synthesis reactions

Measured binary quasifission mass spectra in reactions with actinide nuclides show a large peak in yield near the doubly-magic 208Pb, generally attributed to enhanced binding energy causing a valley in the potential energy surface, which attracts quasifission trajectories. Measurements of binary quasifission mass spectra and cross-sections have been made for reactions of 50Ti with actinide nuclides from 232Th to 249Cf. Cross-sections have also been deduced for sequential fission (a projectile-like nucleus and two fragments from fission of the complementary target-like nucleus). Binary cross-sections fall from 70% of calculated capture cross-sections for 232Th to only 40% for 249Cf, with a compensating increase in sequential fission cross-sections. The data are consistent with the peak in yield near 208Pb originating largely from sequential fission of heavier fragments produced in more mass-asymmetric primary quasifission events. These are increasingly suppressed as the heavy quasifission fragment mass increases above 208Pb. The important role of sequential fission calls for re-interpretation of quasifission observables and dynamics in superheavy element synthesis reactions.

Synthesis and characterization of nano crystallite carboxamide-based iron(III) complexes: SOD mimetic activity, antibacterial and anticancer activity and molecular docking study

Three carboxamide-based ligands and their iron(III) complexes were prepared and structurally characterized. Analytical, thermal and mass spectra measurements showed a 1:1 stoichiometric (M:L) of the synthesized iron(III) complexes. The distorted octahedral geometry of the present iron(III) complexes was assigned based on the results of spectroscopy and magnetometry. Processing of X-ray diffraction data for powder samples by the software Expo 2014 confirmed the octahedral geometry of the three iron(III) complexes. Electrochemical properties of the present iron(III) complexes were studied by cyclic voltammetric measurements. The present iron(III) complexes exhibit SOD like activity with IC50 values of 16.45, 15.24 and 9.70 μM. The drive forces (−λ or ΔG°) controlling these biocatalytic reactions were determined and correlated with catalytic activity. The proposed catalytic mechanistic implications for the conversion of O2 •− to H2O2 and H2O were discussed. The antimicrobial activity has been studied in vitro against G(+) and G(−) pathogenic bacteria. The in vitro anticancer activity of the carboxamide-based ligands and their iron(III) complexes against human Hepatocellular carcinoma (HepG-2) cell lines was examined. The obtained results demonstrated the potent anticancer activity of iron(III) complexes with increased safety on normal cells compared to cisplatin. Molecular docking calculations confirmed the experimental findings of the antibacterial and anticancer activities of both free ligands and their iron(III) chelates. Communicated by Ramaswamy H. Sarma

Electron and ion spectroscopy of azobenzene in the valence and core shells.

Azobenzene is a prototype and a building block of a class of molecules of extreme technological interest as molecular photo-switches. We present a joint experimental and theoretical study of its response to irradiation with light across the UV to x-ray spectrum. The study of valence and inner shell photo-ionization and excitation processes combined with measurement of valence photoelectron-photoion coincidence and mass spectra across the core thresholds provides a detailed insight into the site- and state-selected photo-induced processes. Photo-ionization and excitation measurements are interpreted via the multi-configurational restricted active space self-consistent field method corrected by second order perturbation theory. Using static modeling, we demonstrate that the carbon and nitrogen K edges of azobenzene are suitable candidates for exploring its photoinduced dynamics thanks to the transient signals appearing in background-free regions of the NEXAFS and XPS.

Anion-Directed Self-Assembly of Calix[4]arene-Based Silver(I) Coordination Polymers and Photocatalytic Degradation of Organic Pollutants

Coordination polymers (CPs) have recently emerged as promising candidates for heterogeneous photocatalysis due to their structural designability and tunable properties. Herein, we developed two novel Ag(I)-calix[4]arene coordination polymers with the formula {[Ag2(μ-NO3)L1]}n (CP 1) and {[AgL1]·PF6}n (CP 2) (L1 = 2-mercapto-5-methyl-1,3,4-thiadiazole resorcinol calix[4]arene). Crystallography revealed that anion coordination and self-inclusion behavior induced the cavitand and silver ions to self-assemble into well-defined CPs 1 and 2 with different topological coordination frameworks, respectively. Furthermore, CPs 1 and 2 display high photocatalytic activity for the photodegradation of rhodamine B (RhB) and methyl orange (MO) in an aqueous solution under mild conditions (WLED and UV irradiation). The comparison results demonstrate that CP 1 exhibited better photocatalytic performance than CP 2, which correlated well with the differences in their molecular structure and HOMO-LUMO energy gaps. The photocatalysis products and possible intermediates were successfully monitored and determined using mass spectrum, gas chromatography, and electron paramagnetic resonance measurements. The rational photocatalysis mechanism was further investigated and proposed.

Synthesis, spectroscopic characterization and biological activities as an anticancer and antioxidant of the Pd(II) and Pt(IV) complexes with a new azo dye ligand derived from 5-methyl imidazole

Pd(II) and Pt(IV) metal complexes with new heterocyclic azo dye as ligand 2′-[2′-(1-Hydroxy-4-methyl phenyl) azo]-5-methyl imidazole (HPA-5-MeI) were prepared by reacting a diazonium chloride salt solution of 2-amino-4-methyl phenol with 5-methyl imidazole in an alkaline ethanolic solution. Differing spectral techniques have been used to study the structures of the azo dye ligand (HPA-5-MeI) and chelate complexes such as elemental analysis (C.H.N), Mass spectrum, 1H-NMR, 13C-NMR, FT-IR, UV-Vis, XRD, thermal analysis (TGA/DTA), FE-SEM, and magnetic measurements. The molar conductivity indicates that the Pd(II) complex is not an electrolyte and does not contain conductive species, while the Pt(IV)-complex is the electrolyte because it contains chloride outside the coordination sphere. The results confirmed that the ligand (N, N, O) behaves as a tridentate and coordinates with the metal ion via the nitrogen atom of the azomethine group (C=N) of heterocyclic imidazole molecules, the nitrogen atom of the azo group (N=N), which is the farthest from the imidazole ring, and the oxygen atom of the phenolic ring. Antioxidant studies of synthesized compounds were also performed by measuring the DPPH radical scavenging assay. DPPH radical scavenging was used to measure the antioxidant activity and compare the produced compounds with ascorbic acid, a known antioxidant. However, MTT cytotoxicity assay was used to assess the anticancer and toxicity of ligand (HPA-5-MeI) and Pt(IV)-complex against breast cancer cell line (MCF-7). Furthermore, molecular docking studies have been conducted on the potent compounds that have several crucial interactions with (2XA0) proteins.

Enantioselective Radical Addition to Ketones through Lewis Acid-Enabled Photoredox Catalysis.

Photocatalysis opens up a new window for carbonyl chemistry. Despite a multitude of photochemical reactions of carbonyl compounds, visible light-induced catalytic asymmetric transformations remain elusive and pose a formidable challenge. Accordingly, the development of simple, efficient, and economic catalytic systems is the ideal pursuit for chemists. Herein, we report an enantioselective radical photoaddition to ketones through a Lewis acid-enabled photoredox catalysis wherein the in situ formed chiral N,N'-dioxide/Sc(III)-ketone complex serves as a temporary photocatalyst to trigger single-electron transfer oxidation of silanes for the generation of nucleophilic radical species, including primary, secondary, and tertiary alkyl radicals, giving various enantioenriched aza-heterocycle-based tertiary alcohols in good to excellent yields and enantioselectivities. The results of electron paramagnetic resonance (EPR) and high-resolution mass spectrum (HRMS) measurements provided favorable evidence for the stereocontrolled radical addition process involved in this reaction.

An Experimental and Theoretical Investigation of HCN Production in the Hadean Earth Atmosphere

A critical early stage for the origin of life on Earth may have involved the production of hydrogen cyanide (HCN) in a reducing, predominantly H$_2$ atmosphere. HCN is crucial for the origin of life as it is a possible precursor to several biomolecules that make up RNA and proteins including nucleobases, nucleotides, amino acids, and ribose. In this work, we perform an in depth experimental and theoretical investigation of HCN production in reducing atmospheric conditions (89-95% H$_2$) possibly representing the earliest stages of the Hadean eon, ~4.5-4.3 billion years ago. We make use of cold plasma discharges - a laboratory analog to shortwave UV radiation - to simulate HCN production in the upper layers of the atmosphere for CH$_4$ abundances ranging from 0.1-6.5%. We then combine experimental mass spectrum measurements with our theoretical plasma models to estimate the HCN concentrations produced in our experiments. We find that upper atmospheric HCN production scales linearly with CH$_4$ abundance with the relation [HCN] = 0.13 $\pm$ 0.01[CH$_4$]. Concentrations of HCN near the surface of the Hadean Earth are expected to be about 2-3 orders of magnitude lower. The addition of 1% water to our experiments results in a ~50% reduction in HCN production. We find that four reactions are primarily responsible for HCN production in our experiments: (i) $^4$N + CH$_3$ -> H$_2$CN + H -> HCN + H$_2$, (ii) $^4$N + CH -> CN + H followed by CN + CH$_4$ -> HCN + CH$_3$, (iii) C$_2$H$_4$ + $^4$N -> HCN + CH$_3$, and (iv) $^4$N + $^3$CH$_2$ -> HCN + H. The most prebiotically favorable Hadean atmosphere would have been very rich in CH$_4$ (> 5%), and as a result of greenhouse effects the surface would be likely very hot. In such a prebiotic scenario, it may have been important to incorporate HCN into organic hazes that could later release biomolecules and precursors into the first ponds.

Polar and non-polar fraction from Origanum vulgare spp. hirtum methanolic extract – differences in their bioactivity on Chlamydomonas reinhardtii test system

Aim: To compare the bioactivity of both polar and non-polar fraction of Origanum vulgare spp. hirtum methanolic extract on Chlamydomonas reinhardtii. Material and methods: The polar and non-polar fractions were derived from aerial parts of Origanum vulgare ssp. hirtum, collected during the flowering stage from the ex-situ collection of IBER-BAS. GC/MS analysis of both fractions was done following the standard protocol. The measured mass spectra were deconvoluted by the Automated Mass Spectral Deconvolution and Identification System (AMDIS), before comparison with the databases. Chlamydomonas reinhardtii 137C+ (WT) was used as a test system. Spot-test, cell survival fraction (SF), test of “visible mutations” and CFGE (for measurement of induced DNA double-strand breaks (DSBs)) were applied. Results: The polar fraction did not possess genotoxic, mutagenic as well as DNA-damaging effect. The situation with the non-polar fraction was quite different. Even at the lowest concentration of 250 ppm, cell survival was decreased by 60% (SF = 0.41 ± 0.08). Treatment with concentrations equal to/or greater than 500 ppm resulted in around 100% lethality. A mild mutagenic effect was obtained for the concentration of 250 ppm non-polar fraction (IM = 4.83 ± 0.004). Well-expressed and concentration-dependent induction of DSBs for even the strong DNA fragmentation was observed after the treatment with the non-polar fraction. Conclusions: The different bioactivity of the two fractions correlated well with their different chemical composition. The polar fraction, rich in sugars, organic acids and flavonoid glycosides, did not possess genotoxic and mutagenic potential. The strong genotoxic potential of the non-polar fraction might be related to carvacrol content (37.08%), which is not present in the composition of the polar fraction. To the best of our knowledge, this study provides the first information that the carvacrol-rich non-polar fraction of Origanum vulgare spp. hirtum methanolic extract possesses genotoxic, mutagenic and DNA damaging effect on some low eukaryotes, such as C. reinhardtii. Further experiments with carvacrol should be done in order to clarify the exact mechanism of action.

Evaluation of the efficiency of divalent cobalt and copper chelates based on isatin derivatives and thiosemicarbazide ligands as inhibitors for the corrosion of Sabic iron in acidic medium

Divalent cobalt and copper chelates of the two ligands 1-(1-ethoxycarbonylmethyl-2-oxoindolin-3-ylidene) thiosemicarbazide ( EOIT ) and 1-(1-benzyl-2-oxoindolin-3-ylidene) thiosemicarbazide ( BOIT ) are the target compounds of the current study. Identification of the structures and geometries of these compounds have been performed using the possible physicochemical and analytical instruments. Elemental analysis, molar conductance and thermal analysis assured the composition of the four chelates to be [Co(BOIT)Cl]•1·.5H 2 O ( BOIT-Co ), [Cu(BOIT)Cl] ( BOIT-Cu ), [Co(EOIT)Cl 2 (H 2 O)]•5H 2 O ( EOIT-Co ) and [Cu(EOIT)Cl]•Cl ( EOIT-Cu ) which was further confirmed by the measurement of mass spectra. The architecture arrangement of the ligand atoms around Co and Cu centers has been determined depending on the UV–Vis spectral measurements and calculation of µ eff values. This proved that the copper compounds were square planer whereas the cobalt complexes were tetrahedral or octahedral arrangements. These compounds were examined as corrosion inhibitors for Sabic iron in 1.0 M HCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy, mass-loss and scanning electron microscopy techniques. The acquired outcomes disclosed that the examined compounds were found to have high inhibition efficiencies (% IEs) which were dependent on their concentrations and composition. The obtained high % IEs (83–87% at concentration of 400 mg/l) were interpreted by strong adsorption of the compounds’ molecules on the iron surface and such adsorption was discovered to follow Langmuir adsorption isotherm. At the same concentration, the % IEs are slightly increased in the order: EOIT-Cu > BOIT-Cu > EOIT-Co > BOIT-Co . Finally, the investigational results obtained from all employed techniques were in a good consistent with each other.

Changes in glycosyl inositol phosphoceramides during the cell cycle of the red alga Galdieria sulphuraria

Sphingolipids are significant component of plant-cell plasma membranes, as well as algal membranes, and mediate various biological processes. One of these processes is the change in lipid content during the cell cycle. This change is key to understanding cell viability and proliferation. There are relatively few papers describing highly glycosylated glycosyl inositol phosphorylceramide (GIPC) due to problems associated with the extractability of GIPCs and their analysis, especially in algae.After alkaline hydrolysis of total lipids from the red alga Galdieria sulphuraria, GIPCs were measured by high-resolution tandem mass spectrometry and fragmentation of precursor ions in an Orbitrap mass spectrometer in order to elucidate the structures of molecular species. Fragmentation experiments such as tandem mass spectrometry in the negative ion mode were performed to determine both the ceramide group and polar head structures. Measurement of mass spectra in the negative regime was possible because the phosphate group stabilizes negative molecular ions [M-H]-. Analysisof GIPCs at various stages of the cell cycle provided information on their abundance. It was found that, depending on the phases of the cell cycle, in particular during division, the uptake of all three components of GIPC, i.e., long-chain amino alcohols, fatty acids, and polar heads, changes. Structural modifications of the polar headgroup significantly increased the number of molecular species. Analysis demonstrated a convex characteristic for molecular species with only one saccharide (hexose or hexuronic acid) as the polar head. For two carbohydrates, the course of Hex-HexA was linear, while for HexA-HexA it was concave. The same was true for GIPC with three and four monosaccharides.

A New Pathway for Intersystem Crossing: Unexpected Products in the O(3P) + Cyclopentene Reaction.

We investigated the reaction of O(3P) with cyclopentene at 4 Torr and 298 K using time-resolved multiplexed photoionization mass spectrometry, where O(3P) radicals were generated by 351 nm photolysis of NO2 and reacted with excess cyclopentene in He under pseudo-first-order conditions. The resulting products were sampled, ionized, and detected by tunable synchrotron vacuum ultraviolet radiation and an orthogonal acceleration time-of-flight mass spectrometer. This technique enabled measurement of both mass spectra and photoionization spectra as functions of time following the initiation of the reaction. We observe propylketene (41%), acrolein + ethene (37%), 1-butene + CO (19%), and cyclopentene oxide (3%), of which the propylketene pathway was previously unidentified experimentally and theoretically. The automatically explored reactive potential energy landscape at the CCSD(T)-F12a/cc-pVTZ//ωB97X-D/6-311++G(d,p) level and the related master equation calculations predict that cyclopentene oxide is formed on the singlet potential energy surface, whereas propylketene is first formed on the triplet surface. These calculations provide evidence that significant intersystem crossing can happen in this reaction not only around the geometry of the initial triplet adduct but also around that of triplet propylketene. The formation of 1-butene + CO is initiated on the triplet surface, with bond cleavage and hydrogen transfer occurring during intersystem crossing to the singlet surface. At present, we are unable to explain the mechanistic origins of the acrolein + ethene channel, and we thus refrain from assigning singlet or triplet reactivity to this channel. Overall, at least 60% of the products result from triplet reactivity. We propose that the reactivity of cyclic alkenes with O(3P) is influenced by their greater effective degree of unsaturation compared with acyclic alkenes. This work also suggests that searches for minimum-energy crossing points that connect triplet surfaces to singlet surfaces should extend beyond the initial adducts.

Effect of senescence on biogenic volatile organic compound fluxes in wheat plants

Exchanges of biogenic volatile organic compounds (BVOC) between plants and the atmosphere are likely to vary, in amount and composition, between different plant species but also for a single plant during its development. However, the effect of plant development stages, including senescence, on BVOC exchanges remains poorly investigated, especially in the case of crop plants. We investigated the BVOC exchange patterns for wheat plants, the most grown crop species worldwide, during seed maturation, senescence and after harvest. Fluxes were measured online, in situ, at the plant scale by combining automated chambers and a Proton Transfer - Reaction - Quadrupole ion guide - Time of Flight - Mass Spectrometer (PTR-Qi-Tof-MS). The high resolution and sensitivity of this method enabled the measurement of a large mass spectrum of compounds emitted at very small amounts, allowing a precise characterization of BVOC exchanges. We found that the overall BVOC emissions increased twofold during the senescence stage compared to the maturation stage. Methanol was found to be the most emitted compound (49–60% of the overall flux on a molar basis) followed by acetone (7.5–8.2% of the overall flux on a molar basis) during each developmental stage investigated. Acetaldehyde was another major emitted compound contributing mainly during late senescence to the overall flux (9.7%). When normalized for temperature and light conditions, most BVOC emissions increased during senescence, showing a clear effect of senescence on BVOC exchanges. Chamber emissions were comparable to whole ecosystem fluxes measured at the same site by eddy covariance the previous year. The OH reactivity of the emitted compounds was evaluated based on known reaction rate constants and was the largest during the first senescence stage, peaking at 12 s−1 in the chambers. The results of this study show the need for considering plant phenology when computing BVOC emissions from crops.

Generative Algorithm for Molecular Graphs Uncovers Products of Oil Oxidation.

The autoxidation of triglyceride (or triacylglycerol, TAG) is a poorly understood complex system. It is known from mass spectrometry measurements that, although initiated by a single molecule, this system involves an abundance of intermediate species and a complex network of reactions. For this reason, the attribution of the mass peaks to exact molecular structures is difficult without additional information about the system. We provide such information using a graph theory-based algorithm. Our algorithm performs an automatic discovery of the chemical reaction network that is responsible for the complexity of the mass spectra in drying oils. This knowledge is then applied to match experimentally measured mass spectra with computationally predicted molecular graphs. We demonstrate this methodology on the autoxidation of triolein as measured by electrospray ionization-mass spectrometry (ESI-MS). Our protocol can be readily applied to investigate other oils and their mixtures.

Development of a Data Analysis Tool to Determine the Measurement Variability of Consensus Mass Spectra.

The success of nontargeted analysis often depends on libraries containing reference mass spectra of known chemical compounds; the mass spectra of unknown compounds are compared to these reference mass spectra, leading to a probable compound identity. Typical calculations include the mean measured values for each ion m/z and intensity with no estimation of the variability of the measurement. This study presents a novel tool for the calculation of the variability of a measured mass spectrum, including the various data parameters that can impact the measured variability. Using perfluorooctanoic acid (PFOA) as the model compound, the variability of measured data-dependent fragmentation mass spectra (ddMS2) was calculated within replicate measurements of a simple solution of PFOA and a complex mixture (house dust extract) containing PFOA. The variability of the measured ddMS2 for PFOA in the solution and house dust extract were similar, with standard deviations about the measured m/z value ranging from m/z 0.00003 to 0.00015 and the standard deviations about the measured relative intensity ranging from 0.0077 to 0.0211 relative intensity units. In addition, the selected parameters for the extraction of ddMS2 from a single analytical run varied between the sample types due to the increased presence of background ions in the house dust extract. Finally, the variability of the ddMS2 spectra for PFOA in both samples was used to calculate a more robust similarity factor, informing the confidence of the identification of unknown compounds.

Dynamical simulation of collision-induced dissociation of pyrene dimer cation

We report a theoretical investigation of the collision-induced dissociation of pyrene dimer cation, as recently investigated in the experimental work by Zamith et al. (J. Chem. Phys. 153, 054311 (2020)). Molecular dynamics simulations using potential energies and forces computed at the self-consistent charge density functional-based tight binding level were conducted for different collision energies between 2.5 and 30 eV. It appears that most of the dissociation occurs on a short timescale (less than 3 ps). The dynamical simulations allow to visualize the dissociation processes. At low collision energies, the dissociation cross section increases with collision energies, whereas it remains almost constant for collision energies greater than 10-15 eV. The analysis of the kinetic energy partition is used to get insights into the collision/dissociation processes at the atomic scale. The simulated time-of-flight mass spectra of parent and dissociation products are obtained from the combination of molecular dynamics simulations and phase space theory to address the short and long timescales dissociation, respectively. The agreement between the simulated and measured mass spectra suggests that the main processes are captured by this approach.

Detection of weakly bound clusters in incipiently sooting flames via ion seeded dilution and collision charging for (APi-TOF) mass spectrometry analysis

This study introduces an atmospheric pressure chemical ionization method that relies on low-energy thermal collisions (i.e., <0.05 eV) of aerosolized analytes with bipolar ions pre-seeded in a sample dilution flow and allows for the detection of weakly bound molecular clusters. Herein, the potential of the method is explored in the context of soot inception by performing mass spectrometric analysis of a laminar premixed flame of ethylene and air whose products are sampled through a tiny orifice and quickly diluted in nitrogen pre-flowed through a Kr85 based neutralizer to generate the bipolar ions. Analyses were performed with an Atmospheric Pressure Interface Time-of-Flight (APi-TOF, Tofwerk AG) Mass Spectrometer whose high sensitivity, mass accuracy, and resolution (over 4000) allowed for the discrimination of the flame products from the pre-seeded ions. Since ionization of neutrals occurs by either ion attachment or charge exchange following ion collision, the identification of the origin of each peak in the measured mass spectra is not-trivial. Nevertheless, the results provide valuable information on the overall elemental composition of the neutral flame products ionized in either polarity. Results show that the clustering of hydrocarbons lighter than 400 Da and having a C/H ratio between 2 and 3 leads to soot inception in the flame. The dehydrogenation of the flame products, expected to occur as they are convected in the flame, is observed only for measurements in positive polarity because of a higher probability of soot nuclei and precursors to get a positive rather than a negative charge.

Revisiting the determining fraction of glueball component in f 0 mesons via radiative decays of J/ψ * *Supported by National Natural Science Foundation of China (11805160, 11747040, 11675082, 11605039)

QCD theory predicts the existence of glueballs, but so far all experimental endeavors have failed to identify any such states. To remedy this discrepancy between QCD, which has proven to be a successful theory for strong interactions, and the failure of experimental searches for glueballs, one is tempted to accept the promising interpretation that the glueballs mix with regular states of the same quantum numbers. The lattice estimate of the masses of pure glueballs ranges from 1 to 2 GeV, which is the region of the family. Thus many authors suggest that the mesonic series is an ideal place to study possible mixtures of glueballs and . In this paper, following the strategy proposed by Close, Farrar and Li, we try to determine the fraction of glueball components in mesons using the measured mass spectra and the branching ratios of radiative decays into mesons. Since the pioneering papers by Close et al., more than 20 years have elapsed and more accurate measurements have been done by several experimental collaborations, so it is time to revisit this interesting topic using new data. We suppose and to be pure quark states, while for , and , to fit both the experimental data of radiative decay and their mass spectra, glueball components are needed. Moreover, the mass of the pure glueball is phenomenologically determined.