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Recombination reactions and commissioning of DESIREE

Recombination reactions and commissioning of DESIREE. Åsa Larson & Mats Larsson. Outline. Recombination reactions The H 2 system The HeH system The BeH system Commissioning of DESIREE. Åsa. Mats. Recombination reactions. Recombination reactions ….

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Recombination reactions and commissioning of DESIREE

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  1. Recombination reactions and commissioning of DESIREE Åsa Larson & Mats Larsson

  2. Outline • Recombination reactions • The H2 system • The HeH system • The BeH system • Commissioning of DESIREE Åsa Mats

  3. Recombination reactions

  4. Recombination reactions … • … relevant for the fusion plasma of the divertor. • Light atomic/molecular ions • H, He, Be, …,O • Relative low energies (E<20 eV) • Different isotopes • Different vibrational states v=0,1,2,… • Total cross section, final state • distributionsand differential cross section • H- might be present

  5. Recombination reactions … Electron-molecular ion collisions Dissociative recombination (DR) A+B+ Direct/indirect A++B AB** A++B- AB+ A* +B AB*

  6. Recombination reactions … Electron-molecular ion collisions Resonant ion-pair formation (RIP) A+B+ A++B AB** A++B- AB+ A* +B AB*

  7. Recombination reactions … Electron-molecular ion collisions Vibrational excitation/deexcitation (VE) A+B+ Direct/resonant A++B AB** A++B- AB+ A* +B AB*

  8. Recombination reactions … Electron-molecular ion collisions Dissociative excitation (DE) A+B+ Direct/resonant A++B AB** A++B- AB+ A* +B AB*

  9. Recombination reactions … Anion-cation collisions Mutual neutralization (MN) A+B+ A++B AB** A++B- AB+ A* +B AB*

  10. Recombination reactions … Anion-cation collisions Double charge transfer (DCT) A+B+ A++B AB** A++B- AB+ A* +B AB*

  11. Recombination reactions … Anion-cation collisions Associative ionization (AI) A+B+ A++B AB** A++B- AB+ A* +B AB*

  12. Recombination reactions … Anion-cation collisions Electron detachment (ED) A+B+ A++B AB** A++B- AB+ A* +B AB*

  13. The H2 system

  14. H++H- collisions

  15. The H2 system 1Σg+ H2 adiabatic potential energy curves symmetry

  16. The H2 system 1Σg+ H2 adiabatic potential energy curves symmetry

  17. H+ + H- • Mutual neutralization H+ + H-→H(n) + H • Calculate the cross section for the mutual neutralization reaction at low collision energies (< 100 eV). • Fully quantum mechanical – electronic – vibrational – rotational • Accurate structure calculations • FCI (11s,8p7d,2f) → [9s,8p,7d,2f] • Include all states up the H(n=3)+H and H+ + H- • Strict diabatization • Identical nuclei • Log-derivative method M. Stenrup, Å. Larson and N. Elander, Phys. Rev. A 79, 012713 (2009).

  18. H+ + H- Mutual neutralization Total neutralization cross section M. Stenrup, Å. Larson and N. Elander, Phys. Rev. A 79, 012713 (2009).

  19. H+ + H- Mutual neutralization Branching ratios M. Stenrup, Å. Larson and N. Elander, Phys. Rev. A 79, 012713 (2009).

  20. H+ + H- Double charge transfer H+ + H-→H- + H+ Good agreement with other theoretical studies but a factor of 10 larger than measured ones. J. Zs. Mezei, M. Stenrup, N. Elander and Å. Larson, Phys. Rev. A 82, 014701 (2010).

  21. H+ + H-Mutual neutralization Differential cross section A quantum study is needed! Will be compared with new experiments by X. Urbain!

  22. H+ + H-Mutual neutralization Differential cross section Isotope dependence

  23. H+ + H-Mutual neutralization Why quantum? Semi-classical Landau-Zener study H- +H+ H+H(n=3) Use H+ + H- as a test system! H+H(n=2) Very sensitive to crossing points and coupling strengths! Try different methods to obtain couplings

  24. H+ + H- Mutual neutralization and branching ratios Compare with QM cross section

  25. H+ + H- Mutual neutralization Semi-empirical method: “Olson 1” Effective ionization potential of electron which is transferred from reactants (electron negativity) R. E. Olson, J. R. Peterson and J. Moseley, J. Chem Phys. 53 3391 (1970).

  26. H+ + H- Mutual neutralization Semi-empirical method: “Olson 2” Effective ionization energy of the electron in the product state R. E. Olson, F. T. Smith and E. Bauer, Appl. Opt. 10 1848 (1971).

  27. H+ + H- Mutual neutralization Semi-empirical method: “Olson 3” R. E. Olson, J. Chem Phys. 56 2979 (1972).

  28. H+ + H- Mutual neutralization Using the “Landau-Herring method” “Smirnov” B. M. Smirnov, Sov. Phys. Dokl. 10 218 (1965); 12 242 (1967).

  29. H+ + H- Mutual neutralization Using the “Landau-Herring method” “Janev” R. K. Janev, Adv. At. Mol. Phys. 12 1 (1976).

  30. H+ + H- Mutual neutralization Ab initio 2x2 transformation: Conclusion: Janev and ATD work best!

  31. The HeH system

  32. The HeH system Combining structure and electron scattering calculations Adiabatic resonant states of HeH (FCI) Very highly excited states!

  33. Resonant DE HeH+ + e-→HeH* →He + H+ + e- (Results from previous CRP meeting) C. Strömholm et al., PRA 54 3086 (1996).

  34. Direct DE HeH+ + e-→(HeH+)* + e- →He+ + H + e- Feshbach resonances!? Remove the resonance contribution from the T-matrix Develop a t-dep method C. Strömholm et al., PRA 54 3086 (1996).

  35. The HeH system Non-adiabatic couplings are presently calculated Strict diabatic transformation Quantum study of high-energy DR, RIP and MN. Inclusion of autoionization.

  36. The BeH system

  37. DR of BeH+ Direct DR (Previous CRP meeting) Indirect mechanism + VE:

  38. Mutual neutralization? Be+ + H-→BeH*→Be* + H Avoided crossings with 9 states of 2Σ+ symmetry Ab initio calculations are hard! Semi-classical LZ method with the Janev couplings. J. Pitarch-Ruiz et al., J Chem Phys. 129 054310 (2008)

  39. Mutual neutralization? Be+ + H-→BeH*→Be* + H Large cross section Small isotope effect

  40. Mutual neutralization? Be+ + H-→BeH*→Be* + H Many states contribute

  41. Commissioning of DESIREE • R. D. Thomas, H. T. Schmidt, G. Andler, M. Björkhage, M. Blom, L. Brännholm, E. Bäckström, H. Danared, M. Gatchell, N. Haag, P. Halldén, Dag HanstorpF. Hellberg, H. A. B. Johansson, A. Källberg, G. Källersjö, M. Larsson, S. Leontein, L. Liljeby, P. Löfgren, B. Malm, S. Mannervik, A. Paál, P. Reinhed, K.­G. Rensfelt, S. Rosén, K. Schmidt, A. Simonsson, M. Stockett, J. Weimer, H. Zettergren, and H. Cederquist • Department of Physic, Stockholm University

  42. Detector for neutral reaction products From platform 1 Quadrupole doublet 10° Deflection Drift tube merging section Outer vessel Thermal screen Inner vessel From platform 2 160° Bend Port for laser light Variable deflections

  43. Next step Inject and store ions at room temperature in the asymmetric ring Cool down the ring again to 15 K Start merged beam experiments: H+ + H

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