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Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look

Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look. Holger Kreckel University of Illinois at Urbana-Champaign. … studied in the laboratory. A fundamental process in space …. MWAM 2010, Nov 6th 2010 Holger Kreckel. Neutral fragments. Molecular ion.

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Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look

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  1. Storage ring measurements of the Dissociative Recombination of H3+: a closer look Holger Kreckel University of Illinois at Urbana-Champaign … studied in the laboratory. A fundamental process in space ….

  2. MWAM 2010, Nov6th 2010 Holger Kreckel Neutral fragments Molecular ion Free electron Storage ring measurements … of H3+: a closer look Dissociative recombination of molecular ions AB+ + e- A + B

  3. MWAM 2010, Nov6th 2010 Holger Kreckel O2+ + e-→ O* + O O (1S → 1D) emission at 5577 Å 1st step: DR of O2+ 2nd step: emission from excited atomic products Storage ring measurements … of H3+: a closer look Brief History of Dissociative Recombination (DR) Solar radiation produces a lot of electrons in the Ionosphere by photoionization. How are these electrons removed?

  4. MWAM 2010, Nov6th 2010 Holger Kreckel Direct DR process Storage ring measurements … of H3+: a closer look Dissociative recombination of molecular ions Bates, D.R., “Dissociative Recombination”, Phys. Rev. 78, 492 (1950)

  5. MWAM 2010, Nov6th 2010 Holger Kreckel H2 + H H2 e- H3+ formation and destruction cosmic ray H2 H2+ H3+ H + H + H OH + H2 H2 H3+ H2 e- Water formation OH3+ OH+ OH2+ O H2O + H H2 OH e- HCO+ CO+ C+ H + CO Carbon chemistry Storage ring measurements … of H3+: a closer look Importance of DR in the interstellar medium

  6. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look The Problem with H3+ DR (experiment) H2+H H+H+H H3++e- DR rate coefficient upper limits

  7. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look The Problem with H3+ DR (experiment) H2+H H+H+H H3++e- DR rate coefficient upper limits

  8. MWAM 2010, Nov6th 2010 Holger Kreckel • Vibrations cool • Rotations stay forever Kreckel et al., PRA A 66, 052509 (2002), Kreckel et al., New J. Phys. 6, 151 (2004) Storage ring measurements … of H3+: a closer look Storage ring measurements: concept Advantages •radiative relaxation of internal excitations (rotation, vibration) • direct measurement • 100% detection efficiency • high resolution Problem H3+

  9. MWAM 2010, Nov6th 2010 Holger Kreckel 5 cm Pinhole flange/ground electrode -900 V ring electrode TSR 2004 Cryogenic ion trap H3+ Storage ring measurements … of H3+: a closer look Rotationally “cold” ion sources Gas inlet 2 atm H2 Solenoid valve CRYRING 2002 Supersonic expansion

  10. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Storage ring results with “cold” H3+ ion sources ● TSR electron temp. kT┴=0.5 meV ~ 6K kT||=25 μeV trap temp. 13 K Kreckel, PRL 95, 263201 (2005) ●CRYRING kT┴=2 meV ion temp. 30-50 K McCall, Nature 422, 500 (2003) Theory Kokoouline and Greene

  11. MWAM 2010, Nov6th 2010 Holger Kreckel + + Storage ring measurements … of H3+: a closer look The holy grail: state specific measurements para I = 1/2 ortho I = 3/2 H3+ rotational levels

  12. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Nuclear spin effect: exp. and theory 2005 ۰para H2 ۰normal H2 experiment kT┴=4 meV theory Greene et al. - para - ortho Kreckel et. al, PRL 95, 263201 (2005)

  13. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Theory with more accurate resonance energies S. Fonseca dos Santos et al., JCP 127, 124309 2007

  14. MWAM 2010, Nov6th 2010 Holger Kreckel plunger locking nut discharge electrode skimmer high pressure H2 reservoir low pressure pinhole 6 cm piezo actuator Storage ring measurements … of H3+: a closer look Piezo expansion source

  15. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Rotational temperature of H3+ inferred from cavity ring-down spectroscopy of the ion source pure H2 discharge, 2bar Trot=110 K 1:5 H2:Argon discharge, 2bar Trot=180 K

  16. MWAM 2010, Nov6th 2010 Holger Kreckel para H3+ para H3+ ortho H3+ p-H3+ fraction p3= (47.9 ± 2) % 1:5 n-H2 : Argon mixture p-H3+ fraction p3= (70.8 ± 2) % 1:5 p-H2 : Argon mixture Storage ring measurements … of H3+: a closer look Nuclear spin manipulation

  17. DR 2010, Lake Tahoe, Aug19th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look DR measurements at TSR UI Champaign-Urbana MPI-K Heidelberg Test Storage Ring

  18. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Comparison to CRYRING 2002 TSR 2009 (n-H2:Ar 1:5) CRYRING 2002 (n-H2)

  19. MWAM 2010, Nov6th 2010 Holger Kreckel ne(cooler) = 1.4 x 107 cm-3 ne(target) = 1.34 x 106 cm-3 Storage ring measurements … of H3+: a closer look 2-dimensional imaging of the 3-body breakup H3+ + e- H + H + H

  20. MWAM 2010, Nov6th 2010 Holger Kreckel rotational temperatures (uncertainties ~ 200 K) 950 K 450 K 200 K Storage ring measurements … of H3+: a closer look 2-dimensional imaging of the 3-body breakup H3+ + e- H + H + H

  21. MWAM 2010, Nov6th 2010 Holger Kreckel skimmer Storage ring measurements … of H3+: a closer look Conditions on-axis downstream of the nozzle Collisional heating during Ion extraction?

  22. MWAM 2010, Nov6th 2010 Holger Kreckel Reduced rate coeff. Storage ring measurements … of H3+: a closer look Nuclear spin dependence of the rate coefficient p3= (47.9 ± 2) % 1:5 n-H2 : Argon mixture p3= (70.8 ± 2) % 1:5 p-H2 : Argon mixture Extrapolation: 100% ortho H3+ 100% para H3+

  23. MWAM 2010, Nov6th 2010 Holger Kreckel Still out there … Storage ring measurements … of H3+: a closer look Summary • While we measure a rotational temperature of 200K with CRD spectroscopy, the stored H3+ ions are much hotter than the ion source. • We observed clear differences between different ion sources → the heating is probably happeningprior to injection into the ring. • We observed for the first time detailed structures in the rate coefficients for ortho-H3+ and para-H3+ at low energies. Results: Kreckel et al., 82, 042715 (2010) Petrignani et al., in preparation The holy grail?

  24. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Collaboration TSR Group University of Illinois Kyle N. Crabtree Brian A. Tom Benjamin J. McCall Oldřich Novotny* Annemieke Petrignani Max H. Berg Dennis Bing Manfred Grieser Claude Krantz Michael Lestinsky* Mario B. Mendes Christian Nordhorn Roland Repnow Julia Stützel Andreas Wolf Weizmann Institute Henrik Buhr Stockholm University Richard Thomas *Columbia University, NY German-Israeli Foundation National Science Foundation Max-Planck Society Funding: Eurppean Comission

  25. MWAM 2010, Nov6th 2010 Holger Kreckel Storage ring measurements … of H3+: a closer look Perspectives: the case to continue the quest It is crucial to understand: H3+ + H2 and H3+ (J=1,K=0,1) + e- Next speaker: Kyle Crabtree

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