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Novotný O, Wilhelm P, Paul D, Kálosi Á, Saurabh S, Becker A, Blaum K, George S, Göck J, Grieser M, Grussie F, von Hahn R, Krantz C, Kreckel H, Meyer C, Mishra PM, Muell D, Nuesslein F, Orlov DA, Rimmler M, Schmidt VC, Shornikov A, Terekhov AS, Vogel S, Zajfman D, Wolf A. Quantum-state-selective electron recombination studies suggest enhanced abundance of primordial HeH .. Science 2019; 365:676-679. [PMID: 31320559 DOI: 10.1126/science.aax5921] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 07/01/2019] [Indexed: 11/02/2022]
Abstract
The epoch of first star formation in the early Universe was dominated by simple atomic and molecular species consisting mainly of two elements: hydrogen and helium. Gaining insight into this constitutive era requires a thorough understanding of molecular reactivity under primordial conditions. We used a cryogenic ion storage ring combined with a merged electron beam to measure state-specific rate coefficients of dissociative recombination, a process by which electrons destroy molecular ions. We found a pronounced decrease of the electron recombination rates for the lowest rotational states of the helium hydride ion (HeH+), compared with previous measurements at room temperature. The reduced destruction of cold HeH+ translates into an enhanced abundance of this primordial molecule at redshifts of first star and galaxy formation.
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Affiliation(s)
- Oldřich Novotný
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
| | - Patrick Wilhelm
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Daniel Paul
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Ábel Kálosi
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.,Faculty of Mathematics and Physics, Charles University, 18000 Praha, Czech Republic
| | - Sunny Saurabh
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Arno Becker
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Klaus Blaum
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Sebastian George
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.,Institut für Physik, Universität Greifswald, 17487 Greifswald, Germany
| | - Jürgen Göck
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Manfred Grieser
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Florian Grussie
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Robert von Hahn
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Claude Krantz
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Holger Kreckel
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Christian Meyer
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Preeti M Mishra
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Damian Muell
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Felix Nuesslein
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Dmitry A Orlov
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Marius Rimmler
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Viviane C Schmidt
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Andrey Shornikov
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | | | - Stephen Vogel
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | | | - Andreas Wolf
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
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Guberman SL. The vibrational dependence of dissociative recombination: cross sections for N2+. J Chem Phys 2013; 139:124318. [PMID: 24089778 DOI: 10.1063/1.4821595] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Theoretical ab initio calculations are reported of the cross sections for dissociative recombination of the lowest four excited vibrational levels of N2(+) at electron energies from 0.001 to 1.0 eV. Rydberg vibrational levels contributing to the cross section structures are identified as are dissociative channels contributing more than 10(-16) cm(2) to the total cross sections. In contrast to the prior study of v = 0 (S. L. Guberman, J. Chem. Phys. 137, 074309 (2012)), which showed 2(3)Πu to be the dominant dissociative channel, 4(3)Πu is dominant for v = 1. Both 2 and 4(3)Πu are major routes for dissociative recombination from v = 2-4. Other routes including 2(3)Σu(+), 3(3)Πu, 2(1)Πu, 2(3)Πg, 2(1)Σg(+), 1(1)Δg, and b('1)Σu(+) are significant in narrow energy ranges. The results show that minor dissociative routes, included here for N2(+), must be included in theoretical studies of other molecular ions (including the simplest ions H2(+) and H3(+)) if cross section agreement is to be found with future high resolution dissociative recombination experiments. The calculated predissociation lifetimes of the Rydberg resonances are used in a detailed comparison to two prior storage ring experiments in order to determine if the prior assumption of isotropic atomic angular distributions at "zero" electron energy is justified. The prior experimental assumption of comparable cross sections for v = 0-3 is shown to be the case at "zero" but not at nonzero electron energies. Circumstances are identified in which indirect recombination may be visualized as a firefly effect.
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Affiliation(s)
- Steven L Guberman
- Institute for Scientific Research, 22 Bonad Road, Winchester, Massachusetts 01890, USA
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Abstract
Large scale ab initio calculations are reported for the diabatic (3)Π, (1)Π, (1)Σ(+), (1)Δ, (3)Σ(+), and (3)Δ valence states of CO that provide routes for the dissociative recombination of the ground electronic and vibrational state of CO(+). The most important routes are 2(3)Π, 3(3)Π, 2(1)Π, and D'(1)Σ(+). For electron energies below 0.2961 eV, from the v = 0 ion level, the first two states can generate excited atoms, O((1)D) and C((1)D), but the last two states yield only ground state atoms. From v = 0, hot ground state atoms are generated at 0 eV from each of the four states with C and O having 1.67 and 1.25 eV of kinetic energy, respectively. The potential curves are compared to prior calculations and experiments.
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Affiliation(s)
- Steven L Guberman
- Institute for Scientific Research , 22 Bonad Road, Winchester, Massachusetts 01890, United States
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Thomas RD. When electrons meet molecular ions and what happens next: dissociative recombination from interstellar molecular clouds to internal combustion engines. MASS SPECTROMETRY REVIEWS 2008; 27:485-530. [PMID: 18618616 DOI: 10.1002/mas.20169] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The interaction of matter with its environment is the driving force behind the evolution of 99% of the observed matter in the universe. The majority of the visible universe exists in a state of weak ionization, the so called fourth state of matter: plasma. Plasmas are ubiquitous, from those occurring naturally; interstellar molecular clouds, cometary comae, circumstellar shells, to those which are anthropic in origin; flames, combustion engines and fusion reactors. The evolution of these plasmas is driven by the interaction of the plasma constituents, the ions, and the electrons. One of the most important subsets of these reactions is electron-molecular ion recombination. This process is significant for two very important reasons. It is an ionization reducing reaction, removing two ionised species and producing neutral products. Furthermore, these products may themselves be reactive radical species which can then further drive the evolution of the plasma. The rate at which the electron reacts with the ion depends on many parameters, for examples the collision energy, the internal energy of the ion, and the structure of the ion itself. Measuring these properties together with the manner in which the system breaks up is therefore critical if the evolution of the environment is to be understood at all. Several techniques have been developed to study just such reactions to obtain the necessary information on the parameters. In this paper the focus will be on one the most recently developed of these, the Ion Storage Ring, together with the detection tools and techniques used to extract the necessary information from the reaction.
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Affiliation(s)
- Richard D Thomas
- Department of Physics, Albanova University Centre, Stockholm University, S106 91 Stockholm, Sweden.
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Novotny S, Rubinstein H, Buhr H, Novotný O, Hoffmann J, Mendes MB, Orlov DA, Krantz C, Berg MH, Froese M, Jaroshevich AS, Jordon-Thaden B, Lange M, Lestinsky M, Petrignani A, Shafir D, Zajfman D, Schwalm D, Wolf A. Anisotropy and molecular rotation in resonant low-energy dissociative recombination. PHYSICAL REVIEW LETTERS 2008; 100:193201. [PMID: 18518450 DOI: 10.1103/physrevlett.100.193201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Indexed: 05/26/2023]
Abstract
Angular fragment distributions from the dissociative recombination (DR) of HD(+) were measured with well directed monochromatic low-energy electrons over a dense grid of collision energies from 7 to 35 meV, where pronounced rovibrational Feshbach resonances occur. Significant higher-order anisotropies are found in the distributions, whose size varies along energy in a partial correlation with the relative DR rate from fast-rotating molecules. This may indicate a breakdown of the nonrotation assumption so far applied to predict angular DR fragment distributions.
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Affiliation(s)
- S Novotny
- Max-Planck-Institut für Kernphysik, Heidelberg, Germany
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Guberman SL. Role of excited core Rydberg states in dissociative recombination. J Phys Chem A 2007; 111:11254-60. [PMID: 17547378 DOI: 10.1021/jp070892q] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Intermediate states formed during the dissociative recombination of molecular ions with electrons can play significant roles in determining the magnitude of the total rate coefficient. These resonances are Rydberg states of two types, that is, they can have the ground or excited states of the ion as a core. Those with the excited cores have a fundamentally different excitation mechanism than those with the ground state core. The importance of excited core states in dissociative recombination has received only limited attention in the literature. Theoretical calculations on the dissociative recombination of N2+ are reported which compare the two types of resonances. Potential curves, electronic widths, cross sections, and rate coefficients are calculated for dissociative recombination along the 2(1)Sigma(g)+ state, one of several routes for the dissociative recombination of N2+. The ground core resonances, in this example, are relatively unimportant compared to those with the excited core. Inclusion of the excited core resonances increases the rate coefficient by about a factor of 4 at room temperature, but the increase is not enough to establish 2(1)Sigma(g)+ as the dominant dissociative route.
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Affiliation(s)
- Steven L Guberman
- Institute for Scientific Research, 22 Bonad Road, Winchester, Massachusetts 01890, USA.
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Petrignani A, Hellberg F, Thomas RD, Larsson M, Cosby PC, van der Zande WJ. Electron energy-dependent product state distributions in the dissociative recombination of O2+. J Chem Phys 2005; 122:234311. [PMID: 16008445 DOI: 10.1063/1.1937388] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We present product state distributions and quantum yields from the dissociative recombination reaction of O2+ in its electronic and vibrational ground states as a function of electron collision energy between 0 and 300 meV. The experiments have been performed in the heavy-ion storage ring, CRYRING, and use a cold hollow-cathode discharge source for the production of cold molecular oxygen ions. The branching fractions over the different dissociation limits show distinct oscillations while the resulting product quantum yields are largely independent of electron collision energy above 40 meV. The branching results are well reproduced assuming an isotropic dissociation process, in contrast with recent theoretical predictions.
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Affiliation(s)
- Annemieke Petrignani
- FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ, Amsterdam, The Netherlands.
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Hellberg F, Zhaunerchyk V, Ehlerding A, Geppert WD, Larsson M, Thomas RD, Bannister ME, Bahati E, Vane CR, Osterdahl F, Hlavenka P, af Ugglas M. Investigating the breakup dynamics of dihydrogen sulfide ions recombining with electrons. J Chem Phys 2005; 122:224314. [PMID: 15974675 DOI: 10.1063/1.1930830] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This paper presents results concerning measurements of the dissociative recombination (DR) of dihydrogen sulfide ions. In combination with the ion storage ring CRYRING an imaging technique was used to investigate the breakup dynamics of the three-body channel in the DR of 32SD2(+). The two energetically available product channels S(3P) + 2D(2S) and S(1D) + 2D(2S) were both populated, with a branching fraction of the ground-state channel of 0.6(0.1). Information about the angle between the two deuterium atoms upon dissociation was obtained together with information about how the available kinetic energy was distributed between the two light fragments. The recombination cross sections as functions of energy in the interval of 1 meV to 0.3 eV in the center-of-mass frame are presented for 34SH2(+). The thermal rate coefficient for the DR of 34SH2(+) was determined to be (4.8+/-1.0) x 10(-7)(T/300)(-0.72+/-0.1) cm3 s(-1) over this interval.
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Affiliation(s)
- Fredrik Hellberg
- Department of Physics, Stockholm University, AlbaNova, S-106 91, Stockholm Sweden.
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