The Formation of Molecular Hydrogen on Silicate Dust Analogs: The Rotational Distribution

Gavilan, Lisseth; Lemaire, J. L.; Vidali, Gianfranco; Sabri, T.; Jäger, C.

doi:10.1088/0004-637x/781/2/79

Cited by 20 publications

(21 citation statements)

References 21 publications

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“…This surface reaction occurs when atoms impinge on a surface and either react immediately or diffuse for a short time before they react with already adsorbed atoms 39,40 . Surface mechanisms such as Langmuir-Hinshelwood 41 , Eley-Rideal 42,43 and Hot-atom 35,44,45 also result in ro-vibrationally excited ground state molecules as those produced by the reactions occurring in the plasma volume but they lead to different vibrational distributions. Numerous theoretical and experimental studies have been published mostly for graphite and tungsten 34,43,[46][47][48] and tantalum surfaces have been also employed in filamented plasmas 49,50 or in electron cyclotron resonance (ECR) plasmas 51 .…”

Section: Creation Of Ground State Ro-vibrationally Excited Moleculesmentioning

confidence: 99%

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Béchu

Lemaire

Gavilan

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

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Ro-vibrationally excited molecules of deuterium are involved in non-equilibrium chemical reactions in divertor region of tokamak, molecular assisted recombination, or in neutral beam injector to produce negative ion, dissociative electron attachment, for fusion plasmas. These molecules produced both in a plasma volume and on surfaces are no longer in their electronic ground state X 1 + g (v " 0, J " ) and populate non-uniformly different vibrational (v ) and rotational levels (J ). The high resolution VUV Fourier Transform spectrometer of the DESIRS beam line (SOLEIL synchrotron) is applied to directly scrutinize the ro-vibrationally excited levels of the D 2 ground state from v = 0 to 10 and J up to 8 in an electron cyclotron resonance (ECR) cold plasma. This is performed for different plasma-facing materials, i.e. quartz, tantalum, tungsten, and stainless steel, in order to compare their relative impact in molecular excitation through recombinative desorption from surfaces. A significant effect of these materials on the absolute distribution of the vibrationally states has been found above v > 3. The experimental detection limit for Quartz is v = 7 whereas tungsten and stainlees steel excite the molecules up to v = 9 and tantalum up to v = 10. The use of a bare, temperature-controlled surface of Quartz as a reference, compared to metallic surfaces, allows us to determine the relative production of these excited levels. The recombinative desorption rate on tungsten and stainless steel compared to quartz is ∼2.6 higher and reaches ∼5 for tantalum.

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Section: Creation Of Ground State Ro-vibrationally Excited Moleculesmentioning

confidence: 99%

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Béchu

Lemaire

Gavilan

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

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“…It is worth mentioning that the characterization of H 2 (v 00 ; J 00 ) formed after recombination of H atoms on cold surfaces simulating interstellar grains has been the subject of many experimental studies. [16][17][18] These experiments use REMPI 2 þ 1 (resonantly enhanced multi-photon ionization at 2 þ 1 photons), while the main interest of the synchrotron radiation is to allow direct 1-photon characterization of H 2 (v 00 ; J 00 ).…”

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confidence: 99%

Detection of rovibrationally excited molecular hydrogen in the electronic ground state via synchrotron radiation

Béchu

Aleiferis

Bentounes

et al. 2017

Applied Physics Letters

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International audienceWe describe an original setup named SCHEME (Source of exCited HydrogEn MolEcules) designed to study the recombinative desorption mechanisms of H atoms on a surface by means of high-brilliance monochromatic synchrotron radiation (SR). H atoms are produced on electrically heated filaments under vacuum (in the absence of any discharge) and subsequently recombine on a surface to produce excited hydrogen molecules, namely, H₂(v",J″). Once these levels are produced, they are probed in the vacuum chamber with 5–40 eV (248–31 nm) SR-photons. A preliminary test with Krypton has demonstrated the feasibility of SCHEME to obtain simultaneously VUV-synchrotron radiation induced fluorescence and VUV-absorption signals with room-temperature gas. In order to evaluate the hydrogen molecule dissociation induced by the heated filaments, the absolute density of H atoms has been measured by VUV-absorption. At 1800 K and 100 mTorr, we estimated a dissociation degree of 10⁻⁴, which corresponds to an absolute density of 1.8×10¹⁷ m^{−3/sup>. VUV-absorption spectroscopy is shown to be a valuable tool to detect H₂((v″,J″) molecules up to v″ = 3. Possible improvements of the experimental setup, to detect higher v″ levels, are suggested in the end of this paper}

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“…In REMPI experiments, molecules are first excited to an excited intermediate state by multiple photons, followed by ionization from the intermediate state by another photon or multiple photons. This technique has been applied by a number of groups to near ultraviolet spectroscopy of small molecules (H 2 , H 2 O) desorbed from ices of astrophysical interest in TPD experiments (e.g., [ 128 , 129 ]). However, so far, laser ionization has not gained wide application in the study of COM formation under conditions relevant to astrophysics.…”

Section: Experimental Challenges and Novel Techniquesmentioning

confidence: 99%

Astrochemical Pathways to Complex Organic and Prebiotic Molecules: Experimental Perspectives for In Situ Solid-State Studies

Fulvio

Потапов

et al. 2021

Life

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A deep understanding of the origin of life requires the physical, chemical, and biological study of prebiotic systems and the comprehension of the mechanisms underlying their evolutionary steps. In this context, great attention is paid to the class of interstellar molecules known as “Complex Organic Molecules” (COMs), considered as possible precursors of prebiotic species. Although COMs have already been detected in different astrophysical environments (such as interstellar clouds, protostars, and protoplanetary disks) and in comets, the physical–chemical mechanisms underlying their formation are not yet fully understood. In this framework, a unique contribution comes from laboratory experiments specifically designed to mimic the conditions found in space. We present a review of experimental studies on the formation and evolution of COMs in the solid state, i.e., within ices of astrophysical interest, devoting special attention to the in situ detection and analysis techniques commonly used in laboratory astrochemistry. We discuss their main strengths and weaknesses and provide a perspective view on novel techniques, which may help in overcoming the current experimental challenges.

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The Formation of Molecular Hydrogen on Silicate Dust Analogs: The Rotational Distribution

Cited by 20 publications

References 21 publications

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Detection of rovibrationally excited molecular hydrogen in the electronic ground state via synchrotron radiation

Astrochemical Pathways to Complex Organic and Prebiotic Molecules: Experimental Perspectives for In Situ Solid-State Studies

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