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R-matrix calculations of electron-molecule collisions: scattering from hydrocarbons

R-matrix calculations of electron-molecule collisions: scattering from hydrocarbons. Jonathan Tennyson IAEA Department of Physics and Astronomy University College London Nov 2008.

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R-matrix calculations of electron-molecule collisions: scattering from hydrocarbons

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  1. R-matrix calculations of electron-molecule collisions: scattering from hydrocarbons Jonathan TennysonIAEA Department of Physics and Astronomy University College London Nov 2008 DC arcjet reactor used to grow diamond films at high rates; University of Bristol, UK

  2. Processes at low impact energies Elastic scattering AB+eAB +e Impact ionisation (e,2e) AB+eAB++e + e Electronic excitation AB+eAB* +e Vibrational excitation AB(v”=0)+eAB(v’)+e Rotational excitation AB(N”)+eAB(N’)+e Dissociative attachment / Dissociative recombination AB+eA + B Impact dissociation AB+e A+B+ e Increasing Energy

  3. H H Polyatomic R-matrix method (within the Fixed-Nuclei approximation) Yk=ASi,j ai,j,k fiN hi,j+ Sibj,k fjN+1 fiN= target states = CItarget built from nuclear centred GTOs fjN+1= L2functions e- hi,j = continuum orbitals= GTOscentred on centre of mass (CM) inner region a outer region

  4. Electron scattering from HCCH J. Franz, F.A. Gianturco, K.L. Baluja, J. Tennyson, R. Carey, R. Montuoro, R.R. Lucchese, T. Stoecklin, P. Nicholas & T.L. Gibson, Nucl. Instr. Meths. Phys. Res. B, 266, 425 (2008).

  5. An expert system for running the UK molecular R-matrix codes www.quantemol.com J. Tennyson, D.B. Brown, J.J. Munro, I. Rozum, H.N. Varambhia & N. VinciJ. Phys. Conf. Series, 86, 012001 (2007)

  6. Electron scattering from methane H.N. Varambhia, J.J. Munro & J. Tennyson, Int. J. Mass Spectrometry, 271, 1 (2008).

  7. Electron scattering from methane: Ramsauer minimum H.N. Varambhia, J.J. Munro & J. Tennyson, Int. J. Mass Spectrometry, 271, 1 (2008).

  8. Electron scattering from methane: DCS at 3 eV (expt) H.N. Varambhia, J.J. Munro & J. Tennyson, Int. J. Mass Spectrometry, 271, 1 (2008).

  9. Electron scattering from methane: DCS at 5 eV (expt) H.N. Varambhia, J.J. Munro and J. Tennyson, Int. J. Mass Spectrometry, 271, 1 (2008).

  10. Electron impact ionisation of methane

  11. Electron scattering from ethane H.N. Varambhia, J.J. Munro and J. Tennyson, Int. J. Mass Spectrometry, 271, 1 (2008).

  12. Electron scattering from propane H.N. Varambhia, J.J. Munro and J. Tennyson, Int. J. Mass Spectrometry, 271, 1 (2008).

  13. Intermediate impact energies Ionization AB+eAB+ e+e Ionization and large number of states energetically accessible In principle, an infinite number of states is needed in the close-coupling expansion A few semi-rigorous methods used to treat ionization in this energy range (BEB, DM, etc.) provide an analytical expression for the cross section We have developed and implemented a molecular R-matrix with pseudostates method (MRMPS) for electron-molecule collisions

  14. R-matrix with pseudostates method (RMPS) Yk=ASi,jai,j,kfiN hi,j+ Si bj,kfjN+1 Add fiN not true eigenstates of system: • represent discretized continuum • obtained by diagonalizing target H • must do not represent bound states • transitions to these states give ionization (projection?) Pseudostates

  15. Molecular R-matrix with Pseudostates Method (MRMPS) Polarizability of H3+ (in a.u.)

  16. Electron impact electron detachment of C2- threshold G. Halmova & J. Tennyson, Phys. Rev. Lett., 100, 213202 (2008).

  17. ? Conclusions With the RMPS method for electron molecule collisions we have: • extend energy range of calculations • treat near threshold ionisation • improve representation of polarisation Allows us to treat excitation to high electronic states and collisions with anions (e.g. C2-)

  18. Conclusions • R-matrix method: • flexible • reliable • can treat open shell molecules • extended energy range • larger molecules • available in easy-to-use-version

  19. Hemal Varambhia Jan Franz James Munro Rui Zhang Alex Harvey Alex Harvey Gabriela Halmova electron / positron scatterers

  20. Electron – water rotationally resolved cross sections: Differential cross sections (DCS) at 6 eV Cho et al (2004) * Jung et al (1982) DJ=1 DJ=all DJ=0

  21. Electron – water Momentum transfer cross section Cho et al (2004) Johnstone & Newell

  22. Electron – water (rotationally averaged) elastic cross sections Integral cross section A Faure, JD Gorfinkel & J Tennyson J Phys B, 37, 801 (2004)

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