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Mats Larsson Department of Physics Stockholm University

Progress in measurements of dissociative recombination CRP on Atomic and Molecular Data for Plasma Modelling. Mats Larsson Department of Physics Stockholm University. Task for Stockholm according to minutes of 2005. BeH + and BeH 2 +

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Mats Larsson Department of Physics Stockholm University

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  1. Progress in measurements of dissociative recombinationCRP on Atomic and Molecular Data for Plasma Modelling Mats Larsson Department of Physics Stockholm University

  2. Task for Stockholm according to minutes of 2005 • BeH+ and BeH2+ • Problem: The Manne Siegbahn Laboratory reluctant to deal with Be.

  3. Some points • The Stockholm group has no national funding for fusion related research • The storage ring CRYRING is still in operation and beam time will be scheduled for the fall of 2007. The decision to shut down the lab was taken 2002, so the damage control has been quite successful! • Beam time during 2008 unclear

  4. Progress • Experiment on C4D2+ • Results on CF2+ and CF3+ • The H3+ and its isotopologues • Development of data base for dissociative recombination

  5. e- AB+A Doubly excited neutral molecule + A2+B A+A+B DR of polyatomic ions 3 possible DR - channels A2B+ + e- (Ee) For example: C2H+ + e-  C2 + H + 6.60 eV  CH + C + 3.98 eV  C + C + H + 0.43 eV

  6. What do we measure?: • Branching fractions of dissociative recombination • Thermal rate constants/Cross sections of dissociative recombination (energy/temperature – dependence) Which ions do we study?: - hydrocarbon ions (so far C2H+,C2H2+, C2H3+, C2H4+, C2D5+ C3H4+, C3H7+, C4D9+, C4D2+), CFn+, H3+ Research programme

  7. Manne Siegbahn Laboratory 52 meters circumference

  8. Electron cooling – well defined beam size • Ions interact with electrons – dissociative recombination • Well defined collision energies - velocity matched conditions • Detect neutral fragments (from DR process) ions electrons ions neutrals SBD dipole magnet Interaction - DR Experiment CRYRING Heavy Ion Storage Ring • Long storage time – internal relaxation • Multi-pass experiment

  9. A2+ + e  A + A; no grid 2A Pulse height spectrum Energy

  10. A2+ + e  A + A; grid with 30% transmission A 2A Energy

  11. C2H++e- DR Branching fraction measurement All fragment from one DR event hit the detector at the same time  yield a pulse at an energy corresponding to full beam energy Gives no information about how the molecule breaks up

  12. C2H++e- C C+H 2C 2C+H DR Branching ratio measurement Relate the fragments to different dissociation channels! C2H+ + e-  C2 + H  CH + C  C + C + H

  13. DR Branching ratios – Hydrocarbon ions Results have been compiled by Janev and Reiter (2002, 2004), and by Florerscu-Mitchell and Mitchell (2006) and Adams, Poterya and Babcock (2006)

  14. Viggiano et al. 2005

  15. CF2+ + e  CF + F 714 CF3+ + e  CF2 + F 8010 Ehlerding et al. 2006

  16. CRYRING 2003 ke [cm3s-1] AISA Theory 2000 New theory: PRL 90, 133201 (2003), PRA 68, 012703 (2003)

  17. Kreckel et al., Phys. Rev. Lett. 95, 263201 (2005) TSR H3+ CRYRING

  18. H3+ D3+

  19. D2H+ May 2007, CRYRING

  20. Insulating spacer Solenoid valve H2 para Gas inlet/ 2 atm -900 V/ring electrode Pinhole flange/ground electrode Skimmer

  21. Planned experiment • Ion source will be characterised at the University of Illinois, in Ben McCall’s group with cavity ring-down spectroscopy; critical question: can we produce para-H3+ using para-H2 as feed gas? • Experiment planned for September 2007, one week of beam time has been allocated

  22. Advanced Intergrated Stationary Afterglow Glosik et al. 2005

  23. Glosik et al. 2005

  24. Summary H3+ • Good agreement experiment-theory for dissociative recombination of H3+, D3+ and H2D+ • Several storage ring experiments agree with each other, but disagree with theory • Stationary afterglow experiments for H3+ give almost factor 100 lower rate coefficient than storage rings and theory • Para-H3+ will be used in experiment in CRYRING

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