Communication: Transient Anion States Of Phenol...(h2o) N (n = 1, 2) Complexes: Search For Microsolvation Signatures

We report on the shape resonance spectra of phenol-water clusters, as obtained from elastic electron scattering calculations. Our results, along with virtual orbital analysis, indicate that the well-known indirect mechanism for hydrogen elimination in the gas phase is significantly impacted on by microsolvation, due to the competition between vibronic couplings on the solute and solvent molecules. This fact suggests how relevant the solvation effects could be for the electron-driven damage of biomolecules and the biomass delignification [E. M. de Oliveira et al., Phys. Rev. A 86, 020701(R) (2012)]. We also discuss microsolvation signatures in the differential cross sections that could help to identify the solvated complexes and access the composition of gaseous admixtures of these species. © 2014 AIP Publishing LLC.1415NSF; National Stroke FoundationSanche, L., (2005) Eur. Phys. J. D, 35, p. 367. , For a review, see, 10.1140/epjd/e2005-00206-6Wang, C.-R., Nguyen, J., Lu, Q.-B., (2009) J. Am. Chem. Soc., 131, p. 11320. , 10.1021/ja902675gBaccarelli, I., Bald, I., Gianturco, F.A., Illenberger, E., Kopyra, J., (2011) Phys. Rep., 508, p. 1. , 10.1016/j.physre2011.06.004Bettega, M.H.F., Lima, M.A.P., (2007) J. Chem. Phys., 126, p. 194317. , 10.1063/1.2739514De Oliveira, E.M., Lima, M.A.P., Bettega, M.H.F., Sanchez, S.D.A., Da Costa, R.F., Varella, M.T.D.N., (2010) J. Chem. Phys., 132, p. 204301. , 10.1063/1.3428620Baccarelli, I., Grandi, A., Gianturco, F.A., Lucchese, R.R., Sanna, N., (2006) J. Phys. Chem. B, 110, p. 26240. , 10.1021/jp065872nFabrikant, I.I., Caprasecca, S., Gallup, G.A., Gorfinkiel, J.D., (2012) J. Chem. Phys., 136, p. 184301. , 10.1063/1.4706604Freitas, T.C., Lima, M.A.P., Canuto, S., Bettega, M.H.F., (2009) Phys. Rev. A, 80, p. 062710. , 10.1103/PhysRevA.80.062710Freitas, T.C., Coutinho, K., Varella, M.T.D.N., Lima, M.A.P., Canuto, S., Bettega, M.H.F., (2013) J. Chem. Phys., 138, p. 174307. , 10.1063/1.4803119De Oliveira, E.M., Sanchez, S.D.A., Bettega, M.H.F., Natalense, A.P.P., Lima, M.A.P., Do Varella N, M.T., (2012) Phys. Rev. A, 86, pp. 020701-R. , 10.1103/PhysRevA.86.020701Jordan, K.D., Michejda, J.A., Burrow, P.D., (1976) J. Am. Chem. Soc., 98, p. 7189. , 10.1021/ja00439a014Khatymov, R.V., Muftakhov, M.V., Mazunov, V.A., (2003) Rapid Commun. Mass Spectrom., 17, p. 2327. , 10.1002/rcm.1197Dos Santos, J.S., Da Costa, R.F., Varella, M.T.D.N., (2012) J. Chem. Phys., 136, p. 084307. , 10.1063/1.3687345Bettega, M.H.F., Ferreira, L.G., Lima, M.A.P., (1993) Phys. Rev. A, 47, p. 1111. , 10.1103/PhysRevA.47.1111Da Costa, R.F., Da Paixão, F.J., Lima, M.A.P., (2004) J. Phys. B, 37, pp. L129. , 10.1088/0953-4075/37/6/L03Takatsuka, K., McKoy, V., (1981) Phys. Rev. A, 24, p. 2473. , 10.1103/PhysRevA.24.2473Takatsuka, K., McKoy, V., (1984) Phys. Rev. A, 30, p. 1734. , 10.1103/PhysRevA.30.1734Barreto, R.C., Coutinho, K., Georg, H.C., Canuto, S., (2009) Phys. Chem. Chem. Phys., 11, p. 1388. , 10.1039/b816912h(1998) CRC Handbook of Chemistry and Physics, , 79th ed., edited by D. R. Lide (CRC, Boca Raton)http://dx.doi.org/10.1063/1.4892066Nenner, I., Schulz, G.J., (1975) J. Chem. Phys., 62, p. 1747. , 10.1063/1.430700Winstead, C., McKoy, V., (2007) Phys. Rev. Lett., 98, p. 113201. , 10.1103/PhysRevLett.98.113201Winstead, C., McKoy, V., (2007) Phys. Rev. A, 76, p. 012712. , 10.1103/PhysRevA.76.012712Mažín, Z., Gorfinkiel, J.D., (2011) J. Chem. Phys., 135, p. 144308. , 10.1063/1.3650236Modelli, A., Burrow, P.W., (2004) J. Phys. Chem. A, 108, p. 5721. , 10.1021/jp048759aSchmidt, M.W., Baldridge, K.K., Boatz, J.A., Elbert, S.T., Gordon, M.S., Jensen, J.H., Koseki, S., Montgomery, J.A., (1993) J. Comput. Chem., 14, p. 1347. , 10.1002/jcc.540141112Kossoski, F., Bettega, M.H.F., Varella, M.T.D.N., (2014) J. Chem. Phys., 140, p. 024317. , 10.1063/1.4861589Gallup, G., Burrow, P., Fabrikant, I., (2009) Phys. Rev. A, 79, p. 042701. , 10.1103/PhysRevA.79.042701Gallup, G., Burrow, P., Fabrikant, I., (2009) Phys. Rev. A, 80, p. 046702. , 10.1103/PhysRevA.80.046702Scheer, A.M., Mozejko, P., Gallup, G.A., Burrow, P.D., (2007) J. Chem. Phys., 126, p. 174301. , 10.1063/1.2727460Asmis, K.R., Allan, M., Pyrrole Data in the Gallery of Unpublished EEL Spectra, , http://www.chem.unifr.ch/ma/dir_allan/pyrrole_EELS.pdfHaxton, D.J., McCurdy, C.W., Rescigno, T.N., (2007) Phys. Rev. A, 75, p. 012710. , 10.1103/PhysRevA.75.012710Bode, B.M., Gordon, M.S., (1998) J. Mol. Graphics Modell., 16, p. 133. , 10.1016/S1093-3263(99)00002-9Fuke, K., Kaya, K., (1983) Chem. Phys. Lett., 94, p. 97. , 10.1016/0009-2614(83)87218-

Theoretical and experimental study on electron interactions with chlorobenzene: Shape resonances and differential cross sections

9 págs.; 6 figs.; 1 tab.In this work, we report theoretical and experimental cross sections for elastic scattering of electrons by chlorobenzene (ClB). The theoretical integral and differential cross sections (DCSs) were obtained with the Schwinger multichannel method implemented with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR). The calculations with the SMCPP method were done in the static-exchange (SE) approximation, for energies above 12 eV, and in the static-exchange plus polarization approximation, for energies up to 12 eV. The calculations with the IAM-SCAR method covered energies up to 500 eV. The experimental differential cross sections were obtained in the high resolution electron energy loss spectrometer VG-SEELS 400, in Lisbon, for electron energies from 8.0 eV to 50 eV and angular range from 7 to 110. From the present theoretical integral cross section (ICS) we discuss the low-energy shape-resonances present in chlorobenzene and compare our computed resonance spectra with available electron transmission spectroscopy data present in the literature. Since there is no other work in the literature reporting differential cross sections for this molecule, we compare our theoretical and experimental DCSs with experimental data available for the parent molecule benzene. Published by AIP Publishing.A.S.B., M.T.N.V., S.d’A.S., and M.H.F.B. acknowledge the Brazilian Agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), under CAPES/FCT Programme (Process No. 23038.002465/2014-87). M.T.N.V., S.d’A.S., and M.H.F.B. acknowledge support from the Brazilian Agency Conselho Nacional de Desenvolvimento Científico e Tecnológico. M.H.F.B. acknowledges support from Finep (under project CT-Infra), and M.T.N.V. from São Paulo Research Foundation (FAPESP). A.S.B., S.d’A.S., and M.H.F.B. acknowledge computational support from Professor Carlos M. de Carvalho at LFTC-DFis-UFPR and at LCPADUFPR and from CENAPAD-SP. F.F.S. acknowledges the Portuguese National Funding Agency FCT through researcher Contract No. IF-FCT IF/00380/2014 and together with P.LV. the research Grant No. UID/FIS/00068/2013. F.B. and G.G. acknowledge partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230).Peer Reviewe

Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural

13 págs.; 8 figs.; 6 tabs.We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (CHO). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of CHO. The measurements were carried out at energies in the range 20-40 eV, and for scattered-electron angles between 10°and 90°. The energy resolution of those experiments was typically ∼80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6-50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail. ©2016 AIP Publishing LLCR.F.C.N. thanks CNPq (Brazil) and the Science Without Borders Programme for opportunities to study abroad. D.B.J. thanks the Australian Research Council (ARC) for financial support provided through a Discovery Early Career Research Award, while M.J.B. also thanks the ARC for their support. M.J.B. and M.C.A.L. acknowledge the Brazilian agencies CNPq and FAPEMIG. P.L.-V. acknowledges the Portuguese Foundation for Science and Technology (FCTMEC) through Grant Nos. PTDC/FIS-ATO/1832/2012 and UIO/FIS/00068/2013. G.G. acknowledges partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230) and the European Union COST Action No. CM1301 (CELINA). Finally, R.F.d.C., M.T.d.N.V., M.H.F.B., and M.A.P.L. acknowledge support from the Brazilian agency CNPq and M.T.d.N.V. also thanks FAPESP.Peer Reviewe

Cross-sections for rotational excitations of C

We report elastic (rotationally summed) and rotationally resolved cross-sections for scattering of low-energy electrons by the C3H4 isomers allene, propyne, and cyclopropene, which belong to the D2d, C3v, and C2v groups, respectively. We employed the Schwinger multichannel method with pseudopotentials at the static-exchange approximation, combined with the adiabatic-nuclei-rotation (ANR) approximation to calculate the rotational excitation cross-sections for energies ranging from 5 to 30 eV. Our rotational resolved cross-sections show the isomer effect more strongly related to scattering potentials of different molecular geometries and to transition selection rules than to differences in mass distribution which account for the energy spacing in the rotational spectra of the molecules.

An experimental and theoretical investigation into positron and electron scattering from formaldehyde

We report on measurements of total cross sections (TCSs) for positron scattering from the fundamental organic molecule formaldehyde (CH2O). The energy range of these measurements was 0.26-50.3 eV, whereas the energy resolution was ∼260 meV. To assist us in interpreting these data, Schwinger multichannel level calculations for positron elastic scattering from CH 2O were also undertaken (0.5-50 eV). These calculations, incorporating an accurate model for the target polarization, are found to be in good qualitative agreement with our measured data. In addition, in order to compare the behaviour of positron and electron scattering from this species, independent atom model-screened additivity rule theoretical electron TCSs, now for energies in the range 1-10 000 eV, are also reported. © 2011 IOP Publishing Ltd.GG and FB thank the Spanish Ministerio de Ciencia e Innovacion (project FIS2009-10245), while GG, FB and MJB acknowledge the EU Framework Programme (Cost Actions MP1002 and CM0601). MHFB acknowledges support from ´ FINEP (under Project no CT-Infra).Peer Reviewe

Transient Ions In Electron And Positron Scattering

We report on recent advances in studies of transient ions formed in electron and positron scattering by molecules. We briefly discuss elastic electron collisions against pyrrole and glycine, as well as electron affinities of glycine-water clusters. Positron scattering and annihilation on small molecules is also discussed. © 2009 IOP Publishing Ltd.194Boudäifa, B.E., (2000) Science, 287, p. 1658Pan, X., (2003) Phys. Rev. Lett., 90, p. 208102Sobolewski, A.L., (2002) Phys. Chem. Chem. Phys., 4, p. 1093Perun, S., (2005) J. Am. Chem. Soc., 127, p. 6257Takatsuka, K., McKoy, V., (1984) Phys. Rev., 30, p. 1734Lima, M.A.P., (1990) Phys. Rev., 41, p. 327Germano, J.S.E., Lima, M.A.P., (1993) Phys Rev., 47, p. 3976Bettega, M.H.F., (1993) Phys. Rev., 47, p. 1111Da Costa, R.F., (2004) J. Phys. B: At. Mol. Phys., 37, p. 129O'Malley, T.F., (1966) Phys. Rev., 150, p. 14Dubé, L., Herzenberg, A., (1979) Phys. Rev., 20, p. 194Hazi, A.U., (1981) Phys. Rev., 23, p. 1089Domcke, W., (1991) Phys. Rep., 208, p. 97Varella Do, T.M.N., Lima, M.A.P., (2007) Phys. Rev., 76, p. 052701Varella Do, T.M.N., (2008) Nucl. Instrum. Meth., 266, p. 435D'A, S.S., (2009) Phys. Rev. A, , submittedRichardson, N.A., (2002) J. Am. Chem Soc., 124, p. 10163Richardson, N.A., (2004) J. Am. Chem Soc., 126, p. 4404Kim, S., (2006) J. Chem. Phys., 124, p. 204310Hohenberg, P., Kohn, W., (1964) Phys. Rev., 136 (3 B), p. 864Kohn, W., Sham, L.J., (1965) Phys. Rev., 140 (4), p. 1133Frisch, M.J., (2004) Gaussian03, 1. , (Gaussian, Inc., Wallingford, CT)Zhao, Y., Truhlar, D.G., (2005) J. Chem. Theor. Comput., 1, p. 415Zhao, Y., Truhlar, D.G., (2007) J. Chem. Theor. Comput., 3, p. 289Bettega, M.H.F., Lima, M.A.P., (2007) J. Chem. Phys., 126, p. 194317Rescigno, T.N., (2006) Phys. Rev. Lett., 96, p. 213201Scheer, A.M., (2007) J. Chem. Phys., 126, p. 174301Gallup, G.A., (2009) Phys. Rev., 79, p. 042701Gianturco, F.A., Lucchese, R.R., (2004) J. Phys. Chem., 108, p. 7056Tashiro, M., (2008) J. Chem. Phys., 129, p. 164308Bachrach, S.M., (2008) J. Phys. Chem., 112, p. 3722Sullivan, J.P., (2001) Phys. Rev. Lett., 86, p. 1494Sullivan, J.P., (2001) J. Phys. B: At. Mol. Phys., 34, p. 467Sur, S., Ghosh, A.S., (1985) J. Phys. B: At. Mol. Phys., 18, p. 715Gianturco, F.A., Mukherjee, T., (2001) Phys. Rev., 64, p. 024703Franz, J., Gianturco, F.A., (2006) Eur. Phys. J., 39, p. 407Gilbert, S.J., (2002) Phys. Rev. Lett., 88, p. 04320

Parent anion radical formation in coenzyme Q0: Breaking ubiquinone family rules

We report electron attachment (EA) measurements for the parent anion radical formation from coenzyme Q0 (CoQ0) at low electron energies (<2 eV) along with quantum chemical calculations. CoQ0 may be considered a prototype for the electron withdrawing properties of the larger CoQn molecules, in particular ubiquinone (CoQ10), an electron carrier in aerobic cell respiration. Herein, we show that the mechanisms for the parent anion radical formation of CoQ0 and CoQn (n = 1,2,4) are remarkably distinct. Reported EA data for CoQ1, CoQ2, CoQ4 and para-benzoquinone indicated stabilization of the parent anion radicals around 1.2–1.4 eV. In contrast, we observe for the yield of the parent anion radical of CoQ0 a sharp peak at ∼ 0 eV, a shoulder at 0.07 eV and a peak around 0.49 eV. Although the mechanisms for the latter feature remain unclear, our calculations suggest that a dipole bound state (DBS) would account for the lower energy signals. Additionally, the isoprenoid side chains in CoQn (n = 1,2,4) molecules seem to influence the DBS formation for these compounds. In contrast, the side chains enhance the parent anion radical stabilization around 1.4 eV. The absence of parent anion radical formation around 1.4 eV for CoQ0 can be attributed to the short auto-ionization lifetimes. The present results shed light on the underappreciated role played by the side chains in the stabilization of the parent anion radical. The isoprenoid tails should be viewed as co-responsible for the electron-accepting properties of ubiquinone, not mere spectators of electron transfer reactions

Elastic scattering and vibrational excitation for electron impact on para-IT-benzoquinone

We report on theoretical elastic and experimental vibrational-excitation differential cross sections (DCSs) for electron scattering from para-benzoquinone (C6H4O2), in the intermediate energy range 15-50 eV. The calculations were conducted with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that also now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N-open) at the static-exchange-plus-polarisation (N(open)ch-SEP) level was used to calculate the scattering amplitudes using a channel coupling scheme that ranges from 1ch-SE up to the 89ch-SEP level of approximation. We found that in going from the 38ch-SEP to the 89ch-SEP, at all energies considered here, the elastic DCSs did not change significantly in terms of both their shapes and magnitudes. This is a good indication that our SMCPP 89ch-SEP elastic DCSs are converged with respect to the multichannel coupling effect for the investigated intermediate energies. While agreement between our IAM-SCAR+I and SMCPP 89ch-SEP computations improves as the incident electron energy increases from 15 eV, overall the level of accord is only marginal. This is particularly true at middle scattering angles, suggesting that our SCAR and interference corrections are failing somewhat for this molecule below 50 eV. We also report experimental DCS results, using a crossed-beam apparatus, for excitation of some of the unresolved ("hybrid") vibrational quanta (bands I-III) of para-benzoquinone. Those data were derived from electron energy loss spectra that were measured over a scattered electron angular range of 10 degrees-90 degrees and put on an absolute scale using our elastic SMCPP 89ch-SEP DCS results. The energy resolution of our measurements was similar to 80 meV, which is why, at least in part, the observed vibrational features were only partially resolved. To the best of our knowledge, there are no other experimental or theoretical vibrational excitation results against which we might compare the present measurements. Published by AIP Publishing

Elastic scattering and vibrational excitation for electron impact on para-IT-benzoquinone

We report on theoretical elastic and experimental vibrational-excitation differential cross sections (DCSs) for electron scattering from para-benzoquinone (C6H4O2), in the intermediate energy range 15-50 eV. The calculations were conducted with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that also now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N-open) at the static-exchange-plus-polarisation (N(open)ch-SEP) level was used to calculate the scattering amplitudes using a channel coupling scheme that ranges from 1ch-SE up to the 89ch-SEP level of approximation. We found that in going from the 38ch-SEP to the 89ch-SEP, at all energies considered here, the elastic DCSs did not change significantly in terms of both their shapes and magnitudes. This is a good indication that our SMCPP 89ch-SEP elastic DCSs are converged with respect to the multichannel coupling effect for the investigated intermediate energies. While agreement between our IAM-SCAR+I and SMCPP 89ch-SEP computations improves as the incident electron energy increases from 15 eV, overall the level of accord is only marginal. This is particularly true at middle scattering angles, suggesting that our SCAR and interference corrections are failing somewhat for this molecule below 50 eV. We also report experimental DCS results, using a crossed-beam apparatus, for excitation of some of the unresolved ("hybrid") vibrational quanta (bands I-III) of para-benzoquinone. Those data were derived from electron energy loss spectra that were measured over a scattered electron angular range of 10 degrees-90 degrees and put on an absolute scale using our elastic SMCPP 89ch-SEP DCS results. The energy resolution of our measurements was similar to 80 meV, which is why, at least in part, the observed vibrational features were only partially resolved. To the best of our knowledge, there are no other experimental or theoretical vibrational excitation results against which we might compare the present measurements. Published by AIP Publishing

Electron-impact electronic-state excitation of para-benzoquinone

Angle resolved electron energy loss spectra (EELS) for para-benzoquinone (C6H4O2) have been recorded for incident electron energies of 20, 30, and 40 eV. Measured differential cross sections (DCSs) for electronic band features, composed of a combination of energetically unresolved electronic states, are subsequently derived from those EELS. Where possible, the obtained DCSs are compared with those calculated using the Schwinger multichannel method with pseudopotentials. These calculations were performed using a minimum orbital basis single configuration interaction framework at the static exchange plus polarisation level. Here, quite reasonable agreement between the experimental cross sections and the theoretical cross sections for the summation of unresolved states was observed. Published by AIP Publishing