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Lozano, Ana I., Kateryna Krupa, Filipe Ferreira da Silva, Paulo Limao-Vieira, Francisco Blanco, Antonio Munoz, Darryl B. Jones, Michael J. Brunger, and Gustavo Garcia. "{Low energy electron transport in furfural}." {EUROPEAN PHYSICAL JOURNAL D}. {71} (Submitted). Abstract

{We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed.}

Hoshino, M., P. Limao-Vieira, K. Anzai, H. Kato, H. Cho, D. Mogi, T. Tanioka, F. Ferreira da Silva, D. Almeida, F. Blanco, G. Garcia, O. Ingolfsson, and H. Tanaka. "{Elastic differential cross sections for C4F6 isomers in the 1.5-200 eV energy electron impact: Similarities with six fluorine containing molecules and evidence of F-atom like scattering}." {JOURNAL OF CHEMICAL PHYSICS}. {141} (Submitted). Abstract

{We report absolute elastic differential cross sections for electron interactions with the C4F6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6). The incident electron energy range is 1.5-200 eV, and the scattered electron angular range for the differential measurements varies from 15 degrees to 150 degrees. In all cases the absolute scale of the differential cross section was set using the relative flow technique, with helium as the reference species. Atomic-like behaviour in these scattering systems is shown here for the first time, and is further investigated by comparing the elastic cross sections for the C4F6 isomers with other fluorinated molecules, such as SF6 and CnF6 (n = 2, 3, and 6). We note that for all the six-F containing molecules, the scattering process for electron energies above 30 eV is indistinguishable. Finally, we report results for calculations of elastic differential cross sections for electron scattering from each of these isomers, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements is found to be quite remarkable in all cases. (C) 2014 AIP Publishing LLC.}

Blanco, Francisco, Antonio Munoz, Diogo Almeida, Filipe Ferreira da Silva, Paulo Limao-Vieira, Martina C. Fuss, Ana G. Sanz, and Gustavo Garcia. "{Modelling low energy electron and positron tracks in biologically relevant media}." {EUROPEAN PHYSICAL JOURNAL D}. {67} (Submitted). Abstract

{This colloquium describes an approach to incorporate into radiation damage models the effect of low and intermediate energy (0-100 eV) electrons and positrons, slowing down in biologically relevant materials (water and representative biomolecules). The core of the modelling procedure is a C++ computing programme named ``Low Energy Particle Track Simulation (LEPTS){''}, which is compatible with available general purpose Monte Carlo packages. Input parameters are carefully selected from theoretical and experimental cross section data and energy loss distribution functions. Data sources used for this purpose are reviewed showing examples of electron and positron cross section and energy loss data for interactions with different media of increasing complexity: atoms, molecules, clusters and condense matter. Finally, we show how such a model can be used to develop an effective dosimetric tool at the molecular level (i.e. nanodosimetry). Recent experimental developments to study the fragmentation induced in biologically material by charge transfer from neutrals and negative ions are also included.}

Almeida, D., F. Ferreira da Silva, G. Garcia, and P. Limao-Vieira. "{Dynamic of negative ions in potassium-D-ribose collisions}." {JOURNAL OF CHEMICAL PHYSICS}. {139} (Submitted). Abstract

{We present negative ion formation from collisions of neutral potassium atoms with D-ribose (C5H10O5), the sugar unit in the DNA/RNA molecule. From the negative ion time-of-flight (TOF) mass spectra, OH- is the main fragment detected in the collision range 50-100 eV accounting on average for 50% of the total anion yield. Prominence is also given to the rich fragmentation pattern observed with special attention to O- (16m/z) formation. These results are in sharp contrast to dissociative electron attachment experiments. The TOF mass spectra assignments show that these channels are also observed, albeit with a much lower relative intensity. Branching ratios of the most abundant fragment anions as a function of the collision energy are obtained, allowing to establish a rationale on the collision dynamics. (C) 2013 AIP Publishing LLC.}

Hoshino, M., S. Matejcik, Y. Nunes, F. Ferreira da Silva, P. Limao-Vieira, and H. Tanaka. "{Negative ion formation through dissociative electron attachment to GeH4: Comparative studies with CH4 and SiH4}." {INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}. {306} (Submitted): {51-56}. Abstract

{Negative ion formation by low-energy electron impact to germane (GeH4) has been performed in an electron energy region from 6 to 11 eV with an energy resolution of similar to 500 meV. Anion efficiency curves of four anions have been measured. Product anions are observed mainly in the 6-11 eV energy region, yielding GeHx- (x= 0-3). Comparative studies with methane (CH4) and silane (SiH4) are also presented with the most intense signals observed at 14 amu (CH2-) 31 amu (SiH3-) and 75 amu (GeH3-) from CH4, SiH4 and GeH4, respectively. Fragmentation into these negative ions is attributed to resonant dissociative electron attachment processes. 2011 Elsevier B.V. All rights reserved.}

Mendes, Monica, Khrystyna Regeta, Filipe Ferreira da Silva, Nykola C. Jones, Soren Vronning Hoffmann, Gustavo Garcia, Chantal Daniel, and Paulo Limao-Vieira. "{Comprehensive investigation of the electronic excitation of W(CO)(6) by photoabsorption and theoretical analysis in the energy region from 3.9 to 10.8 eV}." {BEILSTEIN JOURNAL OF NANOTECHNOLOGY}. {8} (Submitted): {2208-2218}. Abstract

{High-resolution vacuum ultraviolet photoabsorption measurements in the wavelength range of 115-320 nm (10.8-3.9 eV) have been performed together with comprehensive relativistic time-dependent density functional calculations (TDDFT) on the low-lying excited sates of tungsten hexacarbonyl, W(CO)(6). The higher resolution obtained reveals previously unresolved spectral features of W(CO)(6). The spectrum shows two higher-energy bands (in the energy ranges of 7.22-8.12 eV and 8.15-9.05 eV), one of them with clear vibrational structure, and a few lower-energy shoulders in addition to a couple of lower-energy metal-to-ligand charge-transfer (MLCT) bands reported in the literature before. Absolute photoabsorption cross sections are reported and, where possible, compared to previously published results. On the basis of this combined experimental/theoretical study the absorption spectrum of the complex has been totally re-assigned between 3.9 and 10.8 eV under the light of spin-orbit coupling (SOC) effects. The present comprehensive knowledge of the nature of the electronically excited states may be of relevance to estimate neutral dissociation cross sections of W(CO)(6), a precursor molecule in focused electron beam induced deposition (FEBID) processes, from electron scattering measurements.}

Ferreira da Silva, F., D. Almeida, E. Vasekova, E. Drage, N. J. Mason, and P. Limao-Vieira. "{High resolution photoabsorption spectrum of hexafluoro-1,3-butadiene (1,3-C4F6) as studied by vacuum ultraviolet (VUV) synchrotron radiation}." {CHEMICAL PHYSICS LETTERS}. {550} (Submitted): {62-66}. Abstract

{In this Letter we present a high resolution VUV photoabsorption spectrum of hexafluoro-1,3-butadiene (1,3-C4F6), over the wavelength range 113-247 nm (11.0-5.0 eV). The spectrum reveals several new features not previously reported in the literature. The assignment of the observed valence and Rydberg transitions and the associated vibronic series is presented based on our recent ab initio calculations on the vertical excitation energies of C4F6 isomers. The dominant excitation has been assigned to the upsilon(1)' (a) C=C stretching mode in the (5(1)A <- 1(1)A, 3p(a) <- pi(a)(20a)) and (7(1)A <- 1(1)A, 3p(b) <- pi(b)(19b)) transitions, with mean energies of 0.201 and 0.188 eV, respectively. The measured absolute photoabsorption cross section has been used to calculate the photolysis lifetime of 1,3-C4F6 in the upper stratosphere (20-50 km). (c) 2012 Elsevier B.V. All rights reserved.}

Ferreira da Silva, F., G. Meneses, O. Ingolfsson, and P. Limao-Vieira. "{Side chain effects in reactions of the potassium-tyrosine charge transfer complex}." {CHEMICAL PHYSICS LETTERS}. {662} (Submitted): {19-24}. Abstract

{Fragmentation of transient negative ions of tyrosine formed, through electron transfer in collisions with neutral potassium atoms is presented in the collision energy range from 30 to 75 eV. At low collision energies the dominating side chain channel observed corresponds to the cleavage of the bond from the para-position of the phenyl ring to the beta-C of the remaining moiety, but cleavage of the C-alpha-C-beta, bond is also observed. Further fragments are formed through cleavage of the C-alpha bond to the carbonyl group, through decomposition of the carboxyl group or through significant decomposition of the backbone. The dehydrogenated molecular anion is also observed with appreciable intensity. These results are discussed in the context of earlier studies on dissociative electron attachment to tyrosine and other amino acids, as well as within the role of the side chain in electron induced decomposition of this aromatic amino acid. Stabilization of the temporary molecular anion in the transient collision complex is discussed and we argue that this may have significant influence on the branching ratios observed. (C) 2016 Published by Elsevier B.V.}

da Silva, Ferreira F., E. Lange, P. Limao-Vieira, N. C. Jones, S. V. Hoffmann, M. - J. Hubin-Franskin, J. Delwiche, M. J. Brunger, R. F. C. Neves, M. C. A. Lopes, E. M. de Oliveira, R. F. da Costa, M. T. N. do Varella, M. H. F. Bettega, F. Blanco, G. Garcia, M. A. P. Lima, and D. B. Jones. "{Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations}." {JOURNAL OF CHEMICAL PHYSICS}. {143} (Submitted). Abstract

{The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range. (C) 2015 AIP Publishing LLC.}

Sulzer, P., A. Mauracher, Ferreira F. da Silva, S. Denifl, T. D. Maerk, M. Probst, P. Limao-Vieira, and P. Scheier. "{Probing royal demolition explosive (1,3,5-trinitro-1,3,5-triazocyclohexane) by low-energy electrons: Strong dissociative electron attachment near 0 eV}." {JOURNAL OF CHEMICAL PHYSICS}. {131} (Submitted). Abstract

{Low energy electron attachment to gas phase royal demolition explosive (RDX) (and RDX-A3) has been performed by means of a crossed electron-molecular beam experiment in an electron energy range from 0 to 14 eV with an energy resolution of similar to 70 meV. The most intense signals are observed at 102 and 46 amu and assigned to C(2)H(4)N(3)O(2)- and NO(2)(-), respectively. Anion efficiency curves of 16 anions have been measured. Product ions are observed mainly in the low energy region, near 0 eV arising from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The remarkable instability of RDX to electron attachment with virtually thermal electrons reflects the highly explosive nature of this compound. The present results are compared to other explosive aromatic nitrocompounds studied in our laboratory recently. (C) 2009 American Institute of Physics. {[}doi:10.1063/1.3230116]}

da Silva, Filipe Ferreira, Carolina Matias, Diogo Almeida, Gustavo Garcia, Oddur Ingolfsson, Helga Dogg Flosadottir, Benedikt Omarsson, Sylwia Ptasinska, Benjamin Puschnigg, Paul Scheier, Paulo Limao-Vieira, and Stephan Denifl. "{NCO-, a Key Fragment Upon Dissociative Electron Attachment and Electron Transfer to Pyrimidine Bases: Site Selectivity for a Slow Decay Process}." {JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY}. {24} (Submitted): {1787-1797}. Abstract

{We report gas phase studies on NCO- fragment formation from the nucleobases thymine and uracil and their N-site methylated derivatives upon dissociative electron attachment (DEA) and through electron transfer in potassium collisions. For comparison, the NCO- production in metastable decay of the nucleobases after deprotonation in matrix assisted laser desorption/ionization (MALDI) is also reported. We show that the delayed fragmentation of the dehydrogenated closed-shell anion into NCO- upon DEA proceeds few microseconds after the electron attachment process, indicating a rather slow unimolecular decomposition. Utilizing partially methylated thymine, we demonstrate that the remarkable site selectivity of the initial hydrogen loss as a function of the electron energy is preserved in the prompt as well as the metastable NCO- formation in DEA. Site selectivity in the NCO- yield is also pronounced after deprotonation in MALDI, though distinctly different from that observed in DEA. This is discussed in terms of the different electronic states subjected to metastable decay in these experiments. In potassium collisions with 1- and 3-methylthymine and 1- and 3-methyluracil, the dominant fragment is the NCO- ion and the branching ratios as a function of the collision energy show evidence of extraordinary site-selectivity in the reactions yielding its formation.}

da Silva, Ferreira F., S. Ptasinska, S. Denifl, D. Gschliesser, J. Postler, C. Matias, T. D. Maerk, P. Limao-Vieira, and P. Scheier. "{Electron interaction with nitromethane embedded in helium droplets: Attachment and ionization measurements}." {JOURNAL OF CHEMICAL PHYSICS}. {135} (Submitted). Abstract

{Results of a detailed study on electron interactions with nitromethane (CH(3)NO(2)) embedded in helium nanodroplets are reported. Anionic and cationic products formed are analysed by mass spectrometry. When the doped helium droplets are irradiated with low-energy electrons of about 2 eV kinetic energy, exclusively parent cluster anions (CH(3)NO(2))(n) are formed. At 8.5 eV, three anion cluster series are observed, i.e., (CH(3)NO(2))(n)(-), {[}(CH(3)NO(2))(n)-H](-), and (CH(3)NO(2))(n)NO(2)(-), the latter being the most abundant. The results obtained for anions are compared with previous electron attachment studies with bare nitromethane and nitromethane condensed on a surface. The cation chemistry (induced by electron ionization of the helium matrix at 70 eV and subsequent charge transfer from He(+) to the dopant cluster) is dominated by production of methylated and protonated nitromethane clusters, (CH(3)NO(2))nCH(3)(+) and (CH(3)NO(2))nH(+). (C) 2011 American Institute of Physics. {[}doi:10.1063/1.3656680]}

Mauracher, A., P. Sulzer, E. Alizadeh, S. Denifl, Ferreira F. da Silva, M. Probst, T. D. Maerk, P. Limao-Vieira, and P. Scheier. "{Electron attachment studies to musk ketone and high mass resolution anionic isobaric fragment detection}." {INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}. {277} (Submitted): {123-129}. Abstract

{Gas phase electron attachment studies have been performed for musk ketone by means of a crossed electron-molecular beams experiment in an energy range from 0 to 15 eV with a resolution of similar to 70 meV. Additional measurements, utilizing a two-sector-field instrument, have been used to distinguish between possible isobaric products. Anion efficiency curves for 19 anions have been measured including a long-lived (metastable) non-dissociated parent anion which is formed at energies near 0eV. Many of the dissociative electron attachment products observed at low energy arise from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The present results are compared with previous aromatic nitrocompounds studied in our laboratory recently. Particularly the close similarity of musk ketone and the explosive trinitrotoluene is of special interest. (C) 2008 Elsevier B.V. All rights reserved.}

Limao-Vieira, P., K. Anzai, H. Kato, M. Hoshino, F. Ferreira da Silva, D. Duflot, D. Mogi, T. Tanioka, and H. Tanaka. "{Electronic Excitation to Singlet States of 1,3-C4F6, c-C4F6 and 2-C4F6 by Electron Impact - Electron Energy-Loss Spectroscopy and ab lnitio Calculations}." {JOURNAL OF PHYSICAL CHEMISTRY A}. {116} (Submitted): {10529-10538}. Abstract

{We report on the first measurements of the electron impact electronic excitation cross sections for C4F6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluorocyclobutene (c-C4F6), and hexafluoro-2-butyne (2-C4F6), measured at 100 eV, 3 degrees scattering angle, while sweeping the energy loss over the range 2.0-15.0 eV. Under these experimental conditions, optically allowed transitions are favored. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. The n = 3 members of the Rydberg series have been assigned converging to the lowest ionization energy limits of the C4F6 isomers and classified according to the magnitude of the quantum defects (delta).}

Barbosa, Souza A., Ferreira F. da Silva, A. Rebelo, S. V. Hoffmann, M. H. F. Bettega, and P. Limao-Vieira. "{Valence and Rydberg Excitations of 2,4-and 2,6-Difluorotoluene as Studied by Vacuum Ultraviolet Synchrotron Radiation and ab lnitio Calculations}." {JOURNAL OF PHYSICAL CHEMISTRY A}. {120} (Submitted): {8998-9007}. Abstract

{Here we report novel comprehensive investigations on the electronic state spectroscopies of isolated 2,4- and 2,6-difluorotoluene in the gas phase by high-resolution vacuum ultraviolet (VUV) photoabsorption measurements in the 4.4-10.8 eV energy range, with absolute cross-section values derived. We also present the first set of ab initio calculations (vertical energies and oscillator strengths), which we have used in the assignment of valence transitions of the difluorotoluene molecules, together with calculated ionization energies to obtain the Rydberg transitions for both molecules. The measured absolute photoabsorption cross sections have been used to estimate the photolysis lifetimes of 2,4- and 2,6-difluorotoluene in the Earth's atmosphere.}

Sanz, A. G., M. C. Fuss, F. Blanco, J. D. Gorfinkiel, D. Almeida, F. Ferreira da Silva, P. Limao-Vieira, M. J. Brunger, and G. Garcia. "{An investigation into electron scattering from pyrazine at intermediate and high energies}." {JOURNAL OF CHEMICAL PHYSICS}. {139} (Submitted). Abstract

{Total electron scattering cross sections for pyrazine in the energy range 10-500 eV have been measured with a new magnetically confined electron transmission-beam apparatus. Theoretical differential and integral elastic, as well as integral inelastic, cross sections have been calculated by means of a screening-corrected form of the independent-atom representation (IAM-SCAR) from 10 to 1000 eV incident electron energies. The present experimental and theoretical total cross sections show a good level of agreement, to within 10%, in the overlapping energy range. Consistency of these results with previous calculations (i.e., the R-matrix and Schwinger Multichannel methods) and elastic scattering measurements at lower energies, below 10 eV, is also discussed. (C) 2013 AIP Publishing LLC.}

Postler, Johannes, Marcelo M. Goulart, Carolina Matias, Andreas Mauracher, Filipe Ferreira da Silva, Paul Scheier, Paulo Limao-Vieira, and Stephan Denifl. "{Dissociative Electron Attachment to the Nitroamine HMX (Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine)}." {JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY}. {24} (Submitted): {744-752}. Abstract

{In the present study, dissociative electron attachment (DEA) measurements with gas phase HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, C4H8N8O8, have been performed by means of a crossed electron-molecular beam experiment. The most intense signals are observed at 46 and 176 u and assigned to NO2 (-) and C3H6N5O4 (-), respectively. Anion efficiency curves for 15 negatively charged fragments have been measured in the electron energy region from about 0-20 eV with an energy resolution of 0.7 eV. Product anions are observed mainly in the low energy region, near 0 eV, arising from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The remarkable instability of HMX towards electron attachment with virtually zero kinetic energy reflects the highly explosive nature of this compound. Substantially different intensity ratios of resonances for common fragment anions allow distinguishing the nitroamines HMX and royal demolition explosive molecule (RDX) in negative ion mass spectrometry based on free electron capture.}

Ribar, Anita, Marian Danko, Juraj Orszagh, Filipe Ferreira da Silva, Ivo Utke, and Stefan Matejcik. "{Dissociative excitation study of iron pentacarbonyl molecule (vol 69, 117, 2015)}." {EUROPEAN PHYSICAL JOURNAL D}. {69} (Submitted). Abstract
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Almeida, D., Ferreira F. da Silva, J. Kopyra, G. Garcia, and P. Limao-Vieira. "{Anion formation in gas-phase potassium-uridine collisions}." {INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}. {365} (Submitted): {243-247}. Abstract

{In this study we report negative ion fragmentation patterns obtained from time-of-flight (TOF) mass spectrometry in potassium-uridine collisions at 30, 70 and 100 eV. The dominant fragments from uridine are also the most abundant from the individual units in potassium collisions with uracil, tetrahydrofuran (THF) and D-ribose. We observe no dehydrogenated parent anion formation. Special emphasis is given to the dissociation mechanisms lending support to the breaking of the N-glycosidic bond as an initial step in the fragmentation of the transient negative ion (TNI). Within their role as sugar unit surrogates, THF and D-ribose (DR) provide useful information for the study of uridine, and presumably other nucleosides from the point of view of DNA/RNA subunits integrity in the biological environment. (C) 2014 Elsevier B.V. All rights reserved.}

Blanco, F., A. Munoz, D. Almeida, F. Ferreira da Silva, P. Limao-Vieira, and G. Garcia. "{Clustering and condensation effects in the electron scattering cross sections from water molecules}." {INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}. {365} (Submitted): {287-294}. Abstract

{Clustering effects in the differential and integral electron scattering cross sections have been investigated by calculating their magnitudes for different water cluster configurations: specifically for the dimer, trimer and tetramer. By assuming that condensation effects can be described in terms of modifications to the single molecule electron scattering cross sections, induced by the surrounding molecules, effective data for liquid water is also provided. Comparison with previous calculations in liquid water has been carried out through the inelastic mean free path, i.e. the mean length between successive inelastic collisions. Although a satisfactory agreement for high energies, above 100 eV, has been found, for lower energies some discrepancies remain and so will be the subject of further investigation. As an example of modelling electron interactions in soft matter, the present set of data has been employed to simulate single electron tracks in liquid water. This was achieved using our Low Energy Particle Track Simulation (LEPTS) code. (C) 2014 Elsevier B.V. All rights reserved.}

Neustetter, Michael, Filipe Ferreira da Silva, and Stephan Denifl. "{Electron interactions with the focused electron beam induced processing (FEBID) precursor tungsten hexachloride}." {RAPID COMMUNICATIONS IN MASS SPECTROMETRY}. {30} (Submitted): {1139-1144}. Abstract

{RationaleSecondary electrons with an energy distribution below 100 eV are formed when high-energy particles interact with matter. In the focused electron beam induced deposition, high-energy beams are used to decompose organometallic compounds on surfaces. We investigated the electron ionisation of WCl6 and dissociative electron attachment to WCl6 in the gas phase in order to better understand the decomposition mechanism driven by secondary electrons. MethodsA double-focusing mass spectrometer coupled with a Nier-type ion source was used to perform the present studies. The electron ionisation studies were performed with an electron energy of 70 eV and dissociative electron attachment studies in the energy range of similar to 0-14 eV. ResultsTungsten hexachloride rapidly oxidises, leading to the formation of a mixture of pure WCl6 and WCl4O together with WCl2O2 species. The fragmentation of the three chlorinated compounds is effective, although electron ionisation to WCl6 leads to W+ in contrast with WCl2O2 and WCl4O leading to WO2+ and WO+, respectively, as lighter fragments. With regard to electron attachment, decomposition of the precursor molecules is observed; however, W- was not detected within the detection limit of the instrument. ConclusionsElectron ionisation and dissociative electron attachment (DEA) to WCl6, WCl4O and WCl2O2 lead to strong fragmentation. In electron ionisation, the fragmentation by loss of chlorine atoms was observed for both WCl6 and the oxidised species. Additionally, the loss of all chlorine ligands is observable for WCl6 as well as the oxidised species. The DEA results have shown dissociation by the scission of chlorine atoms as well as by the scission of an oxygen atom. The formation of chlorine and oxygen anions was observed, indicating the formation of a neutral counterpart containing the metal atom, free to be attacked by the next electron. Copyright (c) 2016 John Wiley & Sons, Ltd.}

da Silva, Ferreira F., J. Rafael, T. Cunha, D. Almeida, and P. Limao-Vieira. "{Electron transfer to aliphatic amino acids in neutral potassium collisions}." {INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}. {365} (Submitted): {238-242}. Abstract

{Electron transfer in potassium collisions with alanine (C3H7NO2) and valine (C3H11NO2) is investigated at 15 and 100 eV. The fragmentation patterns obtained in the unimolecular decomposition through time-of-flight (TOF) mass spectrometry are compared for both amino acids as a function of the collision energy. In the case of alanine, the most prominent feature in the collision regime is the relative decrease of the dehydrogenated parent anion signal with respect to the hydrogen anion as the collision energy increases. For low collision energies this can be rationalised in terms of autodetachment inhibition, whereas at higher collision energies the negative molecular ion can be formed with an excess of internal energy which might even result in fragmentation. Regarding valine, such behaviour was not observed which has been interpreted as a result of side chain effect contributing to an increase of the internal degrees of freedom in comparison to alanine. (C) 2014 Elsevier B.V. All rights reserved.}

Ferreira da Silva, F., M. Lanca, D. Almeida, G. Garcia, and P. Limao-Vieira. "{Anionic fragmentation of glycine upon potassium-molecule collisions}." {EUROPEAN PHYSICAL JOURNAL D}. {66} (Submitted). Abstract

{Electron transfer in potassium collisions with the simplest amino acid glycine has been investigated in the energy range from 20 to 100 eV. In the unimolecular decomposition, fragmentation patterns obtained through TOF mass spectrometry show peculiar differences in comparison with dissociative electron attachment measurements. The most prominent feature in the collision regime is the relative decrease of the dehydrogenated parent anion signal with respect to the hydrogen anion as the collision energy increases. For low collision energies this can be rationalized in terms of autodetachment inhibition, whereas at higher collisions energies the negative molecular ion can be formed with an excess of internal energy which might even result in fragmentation. Metastable decay is here suggested to play a particular role leading to the formation of three anions assigned in the light of recent dissociative electron attachment studies. The formation of isobaric fragments with masses 15, 16 and 26 a. m. u. is also discussed on the basis of the energy available in the electron transfer process.}

Pastega, D. F., E. Lange, J. Ameixa, A. S. Barbosa, F. Blanco, G. Garcia, M. H. F. Bettega, P. Limao-Vieira, and F. Ferreira da Silva. "{Combined experimental and theoretical study on the differential elastic scattering cross sections for acetone by electron impact energy of 7.0-50 eV}." {PHYSICAL REVIEW A}. {93} (Submitted). Abstract

{We report elastic differential cross sections (DCSs) for electron interactions with acetone, C3H6O. The incident electron energy range was 7.0-50 eV, and the scattered electron angular range for the differential measurements varied from 10 degrees to 120 degrees. The calculated cross sections were obtained with two different methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP), and the independent-atom method with screening-corrected additivity rule (IAM-SCAR). The present elastic DCSs have been found to agree well with the results of IAM-SCAR calculations above 20 eV, and also with the SMC calculations below 30 eV. Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. Comparison with previous DCSs shows good agreement albeit the present data is extended down to lower electron impact energies. We find a low-lying pi{*} shape resonance located at 2.6 eV, in agreement with recent results on electron collisions with acetone {[}M. G. P. Homem et al., Phys. Rev. A 92, 032711 (2015)]. The presence of a sigma{*} resonance is also discussed.}

da Silva, Ferreira F., S. Denifl, T. D. Maerk, A. M. Ellis, and P. Scheier. "{Electron attachment to amino acid clusters in helium nanodroplets: Glycine, alanine, and serine}." {JOURNAL OF CHEMICAL PHYSICS}. {132} (Submitted). Abstract

{The first detailed study of electron attachment to amino acid clusters is reported. The amino acids chosen for investigation were glycine, alanine, and serine. Clusters of these amino acids were formed inside helium nanodroplets, which provide a convenient low temperature (0.37 K) environment for growing noncovalent clusters. When subjected to low energy (2 eV) electron impact the chemistry for glycine and alanine clusters was found to be similar. In both cases, parent cluster anions were the major products, which contrasts with the corresponding monomers in the gas phase, where the dehydrogenated products ({[}AA(n)-H](-), where AA=amino acid monomer) dominate. Serine clusters are different, with the major product being the parent anion minus an OH group, an outcome presumably conferred by the facile loss of an OH group from the beta carbon of serine. In addition to the bare parent anions and various fragment anions, helium atoms are also observed attached to both the parent anion clusters and the dehydrogenated parent anion clusters. Finally, we present the first anion yield spectra of amino acid clusters from doped helium nanodroplets as a function of incident electron energy. (C) 2010 American Institute of Physics. {[}doi: 10.1063/1.3429743]}