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Molecular hydrogen interacts more strongly when rotationally excited at low temperatures leading to faster reactions

Abstract

The role of internal molecular degrees of freedom, such as rotation, has scarcely been explored experimentally in low-energy collisions despite their significance to cold and ultracold chemistry. Particularly important to astrochemistry is the case of the most abundant molecule in interstellar space, hydrogen, for which two spin isomers have been detected, one of which exists in its rotational ground state whereas the other is rotationally excited. Here we demonstrate that quantization of molecular rotation plays a key role in cold reaction dynamics, where rotationally excited ortho-hydrogen reacts faster due to a stronger long-range attraction. We observe rotational state-dependent non-Arrhenius universal scaling laws in chemi-ionization reactions of para-H2 and ortho-H2 by He(23P2), spanning three orders of magnitude in temperature. Different scaling laws serve as a sensitive gauge that enables us to directly determine the exact nature of the long-range intermolecular interactions. Our results show that the quantum state of the molecular rotor determines whether or not anisotropic long-range interactions dominate cold collisions.

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Figure 1: Schematic of the experimental set-up.
Figure 2: Interaction potential energy surfaces.
Figure 3: Penning ionization widths.
Figure 4: Reaction rate constants for molecules in excited and ground rotational states with He(23P2) from 10 mK up to 300 K.

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References

  1. Dalgarno, A. in Molecular Hydrogen in Space (eds Combes, F. & Pineau des Forêts, G.) 3 (Cambridge Univ. Press, 2000).

    Google Scholar 

  2. Brünken, S. et al. H2D+ observations give an age of at least one million years for a cloud core forming Sun-like stars. Nature 516, 219–221 (2014).

    Article  Google Scholar 

  3. Herbst, E. Interstellar processes: ortho/para conversion, radiative association, and dissociative recombination. EPJ Web Conf. 84, 06002 (2015).

    Article  Google Scholar 

  4. Smith, I. W. M. Reactions at very low temperatures: gas kinetics at a new frontier. Angew. Chem. Int. Ed. 45, 2842–2861 (2006).

    Article  CAS  Google Scholar 

  5. Clary, D. C. Fast chemical reactions: theory challenges experiment. Annu. Rev. Phys. Chem. 41, 61–90 (1990).

    Article  CAS  Google Scholar 

  6. Herbst, E. Three milieux for interstellar chemistry: gas, dust, and ice. Phys. Chem. Chem. Phys. 16, 3344–3359 (2014).

    Article  CAS  Google Scholar 

  7. Groenenboom, G. C. & Janssen, L. M. C. in Tutorials in Molecular Reaction Dynamics (eds Brouard, M. & Vallance, C.) 392–407 (RSC, 2010).

    Google Scholar 

  8. Langevin, P. Une formule fondamentale de théorie cinétique. Ann. Chim. Phys. 5, 245 (1905).

    CAS  Google Scholar 

  9. Troe, J. Advances in Chemical Physics Vol. 82 (eds Baer, M. & Ng, C.-Y.) 485–529 (Wiley, 1992).

    Google Scholar 

  10. Dashevskaya, E. I., Litvin, I., Nikitin, E. E. & Troe, J. Rates of complex formation in collisions of rotationally excited homonuclear diatoms with ions at very low temperature: application to hydrogen isotopes and hydrogen-containing. J. Chem. Phys. 122, 184311 (2005).

    Article  CAS  Google Scholar 

  11. Olkhov, R. V. & Smith, I. W. M. Rate coefficients for reaction and for rotational energy transfer in collisions between CN in selected rotational levels (X2Σ+, v = 2, N = 0, 1, 6, 10, 15, and 20) and C2H2 . J. Chem. Phys. 126, 134314 (2007).

    Article  Google Scholar 

  12. Ospelkaus, S. et al. Quantum-state controlled chemical reactions of ultracold potassium–rubidium molecules. Science 327, 853–857 (2010).

    Article  CAS  Google Scholar 

  13. Chang, Y.-P. et al. Specific chemical reactivities of spatially separated 3-aminophenol conformers with cold Ca+ ions. Science 342, 98–101 (2013).

    Article  CAS  Google Scholar 

  14. Marquette, J., Rowe, B. R., Dupeyrat, G., Poissant, G. & Rebrion, C. Ion–polar-molecule reactions: a CRESU study of He+, C+, N+H2O, NH3, at 27, 68 and 163 K. Chem. Phys. Lett. 122, 431–435 (1985).

    Article  CAS  Google Scholar 

  15. Rowe, B. R., Marquette, J. B., Dupeyrat, G. & Ferguson, E. E. Reactions of He+ and N+ ions with several molecules at 8 K. Chem. Phys. Lett. 113, 403–406 (1985).

    Article  CAS  Google Scholar 

  16. Ni, K.-K. et al. Dipolar collisions of polar molecules in the quantum regime. Nature 464, 1324–1328 (2010).

    Article  CAS  Google Scholar 

  17. Hudson, E., Gilfoy, N., Kotochigova, S., Sage, J. & DeMille, D. Inelastic collisions of ultracold heteronuclear molecules in an optical trap. Phys. Rev. Lett. 100, 203201 (2008).

    Article  Google Scholar 

  18. Zahzam, N., Vogt, T., Mudrich, M., Comparat, D. & Pillet, P. Atom–molecule collisions in an optically trapped gas. Phys. Rev. Lett. 96, 023202 (2006).

    Article  CAS  Google Scholar 

  19. Staanum, P., Kraft, S. D., Lange, J., Wester, R. & Weidemüller, M. Experimental investigation of ultracold atom–molecule collisions. Phys. Rev. Lett. 96, 023201 (2006).

    Article  Google Scholar 

  20. Jankunas, J., Jachymski, K., Hapka, M. & Osterwalder, A. Observation of orbiting resonances in He(3S1) + NH3 Penning ionization. J. Chem. Phys. 142, 164305 (2015).

    Article  Google Scholar 

  21. Henson, A. B., Gersten, S., Shagam, Y., Narevicius, J. & Narevicius, E. Observation of resonances in Penning ionization reactions at sub-kelvin temperatures in merged beams. Science 338, 234–238 (2012).

    Article  CAS  Google Scholar 

  22. Shagam, Y. & Narevicius, E. Sub-kelvin collision temperatures in merged neutral beams by correlation in phase-space. J. Phys. Chem. C 117, 22454–22461 (2013).

    Article  CAS  Google Scholar 

  23. Jankunas, J., Bertsche, B. & Osterwalder, A. Study of the Ne(3P2) + CH3F electron-transfer reaction below 1 K. J. Phys. Chem. A 118, 3875–3879 (2014).

    Article  CAS  Google Scholar 

  24. Lavert-Ofir, E. et al. Observation of the isotope effect in sub-kelvin reactions. Nature Chem. 6, 332–335 (2014).

    Article  CAS  Google Scholar 

  25. Siska, P. E. Molecular-beam studies of Penning ionization. Rev. Mod. Phys. 65, 337–412 (1993).

    Article  CAS  Google Scholar 

  26. Roberge, W. & Dalgarno, A. The formation and destruction of HeH+ in astrophysical plasmas. Astrophys. J. 255, 489 (1982).

    Article  CAS  Google Scholar 

  27. Lique, F., Li, G., Werner, H.-J. & Alexander, M. H. Communication: non-adiabatic coupling and resonances in the F + H2 reaction at low energies. J. Chem. Phys. 134, 231101 (2011).

    Article  Google Scholar 

  28. Holmgren, S. L., Waldman, M. & Klemperer, W. Internal dynamics of van der Waals complexes. I. Born–Oppenheimer separation of radial and angular motion. J. Chem. Phys. 67, 4414 (1977).

    Article  CAS  Google Scholar 

  29. Dubernet, M.-L. & Hutson, J. M. Atom–molecule van der Waals complexes containing open-shell atoms. I. General theory and bending levels. J. Chem. Phys. 101, 1939 (1994).

    Article  CAS  Google Scholar 

  30. Kirste, M. et al. Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals. Science 338, 1060–1063 (2012).

    Article  CAS  Google Scholar 

  31. Makrides, C. et al. Ultracold chemistry with alkali-metal–rare-earth molecules. Phys. Rev. A 91, 012708 (2015).

    Article  Google Scholar 

  32. Buckingham, A. D. Molecular quadrupole moments. Q. Rev. Chem. Soc. 13, 183 (1959).

    Article  Google Scholar 

  33. Gorin, E. Photolysis of aldehydes and ketones in the presence of iodine vapor. J. Chem. Phys. 7, 256 (1939).

    Article  CAS  Google Scholar 

  34. Veatch, G. & Oskam, H. Collision processes occurring in decaying plasmas produced in helium–hydrogen mixtures. Phys. Rev. A 8, 389–396 (1973).

    Article  CAS  Google Scholar 

  35. Jachymski, K., Krych, M., Julienne, P. S. & Idziaszek, Z. Quantum-defect model of a reactive collision at finite temperature. Phys. Rev. A 90, 042705 (2014).

    Article  Google Scholar 

  36. Gribakin, G. & Flambaum, V. Calculation of the scattering length in atomic collisions using the semiclassical approximation. Phys. Rev. A 48, 546–553 (1993).

    Article  CAS  Google Scholar 

  37. Sadeghpour, H. R. et al. Collisions near threshold in atomic and molecular physics. J. Phys. B 33, R93–R140 (2000).

    Article  CAS  Google Scholar 

  38. Wigner, E. On the behavior of cross-sections near thresholds. Phys. Rev. 73, 1002–1009 (1948).

    Article  CAS  Google Scholar 

  39. Gao, B. Universal model for exoergic bimolecular reactions and inelastic processes. Phys. Rev. Lett. 105, 263203 (2010).

    Article  Google Scholar 

  40. Nesbitt, D. J. High-resolution infrared spectroscopy of weakly bound molecular complexes. Chem. Rev. 88, 843–870 (1988).

    Article  CAS  Google Scholar 

  41. Even, U., Jortner, J., Noy, D., Lavie, N. & Cossart-Magos, C. Cooling of large molecules below 1 K and He clusters formation. J. Chem. Phys. 112, 8068 (2000).

    Article  CAS  Google Scholar 

  42. Wiley, W. C. & McLaren, I. H. Time-of-flight mass spectrometer with improved resolution. Rev. Sci. Instrum. 26, 1150 (1955).

    Article  CAS  Google Scholar 

  43. Luria, K., Lavie, N. & Even, U. Dielectric barrier discharge source for supersonic beams. Rev. Sci. Instrum. 80, 104102 (2009).

    Article  CAS  Google Scholar 

  44. Metcalf, H. J. & van der Straten, P. Laser Cooling and Trapping (Springer, 1999).

    Book  Google Scholar 

  45. Martin, D. W., Weiser, C., Sperlein, R. F., Bernfeld, D. L. & Siska, P. E. Collision energy dependence of product branching in Penning ionization: He*(21S, 23S) + H2, D2, and HD. J. Chem. Phys. 90, 1564 (1989).

    Article  CAS  Google Scholar 

  46. Pratt, S. T., Dehmer, P. M. & Dehmer, J. L. Photoionization of excited molecular states. H2 C 1Πu . Chem. Phys. Lett. 105, 28–33 (1984).

    Article  CAS  Google Scholar 

  47. Hapka, M., Chałasiński, G., Kłos, J. & Żuchowski, P. S. First-principle interaction potentials for metastable He(3S) and Ne(3P) with closed-shell molecules: application to Penning-ionizing systems. J. Chem. Phys. 139, 014307 (2013).

    Article  Google Scholar 

  48. Hapka, M., Żuchowski, P. S., Szczęśniak, M. M. & Chałasiński, G. Symmetry-adapted perturbation theory based on unrestricted Kohn–Sham orbitals for high-spin open-shell van der Waals complexes. J. Chem. Phys. 137, 164104 (2012).

    Article  Google Scholar 

  49. Bishop, D. M. & Pipin, J. Dipole, quadrupole, octupole, and dipole–octupole polarizabilities at real and imaginary frequencies for H, He, and H2 and the dispersion-energy coefficients for interactions between them. Int. J. Quantum Chem. 45, 349–361 (1993).

    Article  CAS  Google Scholar 

  50. Werner, H.-J. et al. MOLPRO, version 2012.1; http://www.molpro.net

  51. Aidas, K. et al. The Dalton quantum chemistry program system. Wiley Interdiscip. Rev.: Comput. Mol. Sci. 4, 269 (2014).

    CAS  Google Scholar 

  52. Averbukh, V. & Cederbaum, L. S. Ab initio calculation of interatomic decay rates by a combination of the Fano ansatz, Green's-function methods, and the Stieltjes imaging technique. J. Chem. Phys. 123, 204107 (2005).

    Article  Google Scholar 

  53. Gokhberg, K., Averbukh, V. & Cederbaum, L. S. Decay rates of inner-valence excitations in noble gas atoms. J. Chem. Phys. 126, 154107 (2007).

    Article  CAS  Google Scholar 

  54. Kopelke, S., Gokhberg, K., Averbukh, V., Tarantelli, F. & Cederbaum, L. S. Ab initio interatomic decay widths of excited states by applying Stieltjes imaging to Lanczos pseudospectra. J. Chem. Phys. 134, 094107 (2011).

    Article  CAS  Google Scholar 

  55. Extensible Computational Chemistry Environment Basis Set Database, Version 02/25/04 (Molecular Science Computing Facility, Environmental and Molecular Sciences Laboratory, Pacific Northwest Laboratory).

  56. Kaufmann, K., Baumeister, W. & Jungen, M. Universal Gaussian basis sets for an optimum representation of Rydberg and continuum wavefunctions. J. Phys. B 22, 2223–2240 (1989).

    Article  CAS  Google Scholar 

  57. Langhoff, P. in Electron–Molecule and Photon–Molecule Collisions (eds Rescigno, T., McKoy, V. & Schneider, B.) 183 (Plenum, 1979).

    Google Scholar 

  58. Aquilante, F. et al. MOLCAS 7: the next generation. J. Comput. Chem. 31, 224–247 (2010).

    Article  CAS  Google Scholar 

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Acknowledgements

The authors thank R. Kosloff and R. Moszynski for discussions as well as O. Tal and D. Rakhmilevitch for advice and help in the generation of para-hydrogen. This research was made possible, in part, by the historic generosity of the Harold Perlman family. The authors acknowledge financial support from the European Commission through ERC grant EU-FP7-ERC-CoG 1485 QuCC (Y.S., A.K., E.N.), from the Alexander von Humboldt Foundation (W.S.), from the Lee Family Foundation (R.Y.) and from the UK's Engineering and Physical Sciences Research Council (V.A., R.Y.) through the Career Acceleration Fellowship (award EP/H003657/1) and the Programme Grant on Attosecond Dynamics (award EP/I032517), as well as from the Deutsche Forschungsgemeinschaft through Research Unit 1789 (V.A.).

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The experimental work and data analysis were carried out by Y.S., A.K. and E.N. Ab initio potential surfaces and interaction strengths were calculated by W.S. The ionization widths were calculated by R.Y. and V.A. All authors contributed to the discussion of experimental results, derivation of the theoretical model and writing of the manuscript.

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Correspondence to Edvardas Narevicius.

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The authors declare no competing financial interests.

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Shagam, Y., Klein, A., Skomorowski, W. et al. Molecular hydrogen interacts more strongly when rotationally excited at low temperatures leading to faster reactions. Nature Chem 7, 921–926 (2015). https://doi.org/10.1038/nchem.2359

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