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Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look Holger Kreckel University of Illinois at Urbana-Champaign A fundamental.

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Presentation on theme: "Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look Holger Kreckel University of Illinois at Urbana-Champaign A fundamental."— Presentation transcript:

1 Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look Holger Kreckel University of Illinois at Urbana-Champaign A fundamental process in space …. … studied in the laboratory.

2 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look AB + + e - A + B Dissociative recombination of molecular ions Molecular ion Free electron Neutral fragments

3 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look Brief History of Dissociative Recombination (DR) O 2 + + e - → O* + O 1 st step: DR of O 2 + O ( 1 S → 1 D) emission at 5577 Å 2 nd step: emission from excited atomic products Solar radiation produces a lot of electrons in the Ionosphere by photoionization. How are these electrons removed?

4 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look Dissociative recombination of molecular ions Direct DR process Bates, D.R., “Dissociative Recombination”, Phys. Rev. 78, 492 (1950)

5 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look Importance of DR in the interstellar medium H 3 + formation and destruction H 2 H 2 + H 3 + cosmic ray H2H2 H 2 + H H + H + H e-e- O H3+H3+ OH + OH 2 + H2H2 OH 3 + H2H2 e-e- OH + H 2 H 2 O + H Water formation C+C+ OH CO + H2H2 HCO + e-e- H + CO Carbon chemistry

6 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look H 3 + +e - H 2 +H H+H+H The Problem with H 3 + DR (experiment) upper limits DR rate coefficient

7 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look H 3 + +e - H 2 +H H+H+H The Problem with H 3 + DR (experiment) upper limits DR rate coefficient

8 Storage ring measurements: concept radiative relaxation of internal excitations (rotation, vibration) direct measurement 100% detection efficiency high resolution Advantages Problem H3+H3+ MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look Vibrations cool Rotations stay forever Kreckel et al., PRA A 66, 052509 (2002), Kreckel et al., New J. Phys. 6, 151 (2004)

9 H2H2 Gas inlet 2 atm Solenoid valve -900 V ring electrode Pinhole flange/ground electrode H3+H3+ Rotationally “cold” ion sources Supersonic expansion CRYRING 2002 5 cm Cryogenic ion trap TSR 2004 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

10 ● 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) Storage ring results with “cold” H 3 + ion sources Theory Kokoouline and Greene MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

11 + ortho I = 3/2 para I = 1/2 + The holy grail: state specific measurements H 3 + rotational levels MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

12 Nuclear spin effect: exp. and theory 2005 ۰para H 2 ۰normal H 2 experiment kT ┴ =4 meV theory Greene et al. - para - ortho Kreckel et. al, PRL 95, 263201 (2005) MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

13 Theory with more accurate resonance energies S. Fonseca dos Santos et al., JCP 127, 124309 2007 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

14 skimmer discharge electrode pinhole plunger piezo actuator locking nut 6 cm high pressure H 2 reservoir low pressure Piezo expansion source MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

15 Rotational temperature of H 3 + inferred from cavity ring-down spectroscopy of the ion source pure H 2 discharge, 2bar T rot =110 K 1:5 H 2 :Argon discharge, 2bar T rot =180 K MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

16 Nuclear spin manipulation 1:5 n-H 2 : Argon mixture p-H 3 + fraction p 3 = (47.9 ± 2) % 1:5 p-H 2 : Argon mixture p-H 3 + fraction p 3 = (70.8 ± 2) % ortho H 3 + para H 3 + MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

17 DR 2010, Lake Tahoe, Aug 19th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look UI Champaign-Urbana MPI-K Heidelberg DR measurements at TSR T est S torage R ing

18 Comparison to CRYRING 2002 CRYRING 2002 (n-H 2 ) TSR 2009 (n-H 2 :Ar 1:5) MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

19 2-dimensional imaging of the 3-body breakup H 3 + + e - H + H + H n e (cooler) = 1.4 x 10 7 cm -3 n e (target) = 1.34 x 10 6 cm -3 MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

20 2-dimensional imaging of the 3-body breakup 950 K 450 K 200 K rotational temperatures (uncertainties ~ 200 K) H 3 + + e - H + H + H MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

21 Conditions on-axis downstream of the nozzle Collisional heating during Ion extraction? skimmer MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

22 Nuclear spin dependence of the rate coefficient 1:5 n-H2 : Argon mixture 1:5 p-H2 : Argon mixture p 3 = (47.9 ± 2) % p 3 = (70.8 ± 2) % Extrapolation: 100% ortho H 3 + 100% para H 3 + Reduced rate coeff. MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

23 Summary While we measure a rotational temperature of 200K with CRD spectroscopy, the stored H 3 + ions are much hotter than the ion source. We observed clear differences between different ion sources → the heating is probably happening prior to injection into the ring. We observed for the first time detailed structures in the rate coefficients for ortho-H 3 + and para-H 3 + at low energies. The holy grail? Still out there … Results: Kreckel et al., 82, 042715 (2010) Petrignani et al., in preparation MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

24 Collaboration 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 TSR Group University of Illinois Richard Thomas Stockholm University Henrik Buhr Weizmann Institute *Columbia University, NY Funding: National Science Foundation Max-Planck Society German-Israeli Foundation Eurppean Comission MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

25 Perspectives: the case to continue the quest Next speaker: Kyle Crabtree It is crucial to understand: H 3 + + H 2 and H 3 + (J=1,K=0,1) + e - MWAM 2010, Nov 6th 2010 Holger Kreckel Storage ring measurements … of H 3 + : a closer look

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