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Spectroscopic measurements of the reaction H 3 + + H 2  H 2 + H 3 +

Spectroscopic measurements of the reaction H 3 + + H 2  H 2 + H 3 +. Kyle N. Crabtree , Carrie A. Kauffman, Brian A. Tom, Eftalda Becka, Brett A. McGuire, Benjamin J. McCall University of Illinois. 1/2. 3/2. para-H 3 +. ortho-H 3 +. H 3 + + H 2  H 2 + H 3 +.

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Spectroscopic measurements of the reaction H 3 + + H 2  H 2 + H 3 +

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  1. Spectroscopic measurements of the reaction H3+ + H2 H2 + H3+ Kyle N. Crabtree, Carrie A. Kauffman, Brian A. Tom, Eftalda Becka, Brett A. McGuire, Benjamin J. McCall University of Illinois

  2. 1/2 3/2 para-H3+ ortho-H3+ H3+ + H2 H2 + H3+ H3+ + H2 reaction important for thermalization of H3+ in interstellar clouds (see TF09, 160 MA, 3:52 pm) 1 “identity” H5+ 3 “hop” a = kH/kE 6 “exchange” 66th OSU International Symposium on Molecular Spectroscopy

  3. Previous experimental work M. Cordonnier et al., J. Chem. Phys. (2000), 113, 3181-3193. a = 2.4 + 0.6 @ 400 K 66th OSU International Symposium on Molecular Spectroscopy

  4. Experimental data Other experimental work hop exch hop:exchange a increases with increasing T temperature 66th OSU International Symposium on Molecular Spectroscopy

  5. Experimental setup 66th OSU International Symposium on Molecular Spectroscopy

  6. Hollow cathode cell 66th OSU International Symposium on Molecular Spectroscopy

  7. Target transitions R(3,0) 2930.1 cm-1 R(3,1)u 2928.3 cm-1 R(3,2)u 2923.3 cm-1 R(3,3)l 2829.9 cm-1 R(2,1)u 2826.1 cm-1 Kinetic and rotational temperature p-H3+ fraction (p3) R(2,2)l 2762.1 cm-1 R(1,0) 2725.9 cm-1 R(1,1)u 2726.2 cm-1 66th OSU International Symposium on Molecular Spectroscopy

  8. H3+ pressure dependence Liquid N2 cooled cell (135 K) Uncooled cell (350 K) • Decrease in H3+ number density with increasing pressure • 3-body collisions (H3+ + 2H2 H5+ + H2) • To measure hop:exchange ratio of the bimolecular H3+ + H2 reaction, measure p3 as a function of p2 at two pressures for each temperature 66th OSU International Symposium on Molecular Spectroscopy

  9. H3+/H2 para fraction relationships Liquid N2 cooled cell (135 K) Uncooled cell (350 K) 3-body HT Low temperature 2-body HT 66th OSU International Symposium on Molecular Spectroscopy

  10. Uncooled plasma (350 K) fit No evidence for influence of nuclear-spin-dependent 3-body collisions in data 66th OSU International Symposium on Molecular Spectroscopy

  11. Liquid N2 cooled plasma (135 K) modeling Tkin= 135 K 66th OSU International Symposium on Molecular Spectroscopy

  12. Summary of experimental data a = 2.2 + 0.3 T = 450 K a decreases with temperature: 1.6 at 350 K down to 0.5 at 135 K 66th OSU International Symposium on Molecular Spectroscopy

  13. H3+ + H2 H2 + H3+ 1 “identity” H5+ 3 “hop” 6 “exchange” 66th OSU International Symposium on Molecular Spectroscopy

  14. D2d C2v Dynamics of Reaction PES: Z. Xie, B. J. Braams, & J. M. Bowman, J. Chem. Phys. (2005) 122, 224307. C2v 3000 cm-1 1500 cm-1 50 cm-1 hop exchange Hop is dynamically faster than exchange; short complex lifetime favors hop At low temperatures, “statistical” hop/exchange = 0.5 seems valid 66th OSU International Symposium on Molecular Spectroscopy

  15. Acknowledgements Kisam Park More information: Tomorrow, TF09, 160 MA K. N. Crabtree, B. A. Tom, B. J. McCall, J. Chem. Phys. (2011) 134, 194310. K. N. Crabtree et al., J. Chem. Phys. (2011) 134, 194311. http://bjm.scs.illinois.edu 66th OSU International Symposium on Molecular Spectroscopy

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