Experimental Approach to Physicochemical Hydrogen Processes on Cosmic Ice Dust

Watanabe, Naoki; Tsuge, Masashi

doi:10.7566/jpsj.89.051015

Cited by 6 publications

(6 citation statements)

References 99 publications

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“…Moreover, we found that H 2 was formed efficiently on the DLC even at 20 K, which is higher than the threshold for H 2 formation on ASW. However, the formation at 20…”

Section: Hydrogen Reactions On Icy Grainsmentioning

confidence: 99%

Radical reactions on interstellar icy dust grains: Experimental investigations of elementary processes

Tsuge

Watanabe

2023

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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Molecular clouds (MCs) in space are the birthplace of various molecular species. Chemical reactions occurring on the cryogenic surfaces of cosmic icy dust grains have been considered to play important roles in the formation of these species. Radical reactions are crucial because they often have low barriers and thus proceed even at low temperatures such as 910 K. Since the 2000s, laboratory experiments conducted under low-temperature, high-vacuum conditions that mimic MC environments have revealed the elementary physicochemical processes on icy dust grains. In this review, experiments conducted by our group in this context are explored, with a focus on radical reactions on the surface of icy dust analogues, leading to the formation of astronomically abundant molecules such as H 2 , H 2 O, H 2 CO, and CH 3 OH and deuterium fractionation processes. The development of highly sensitive, non-destructive methods for detecting adsorbates and their utilization for clarifying the behavior of free radicals on ice, which contribute to the formation of complex organic molecules, are also described.

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“…Moreover, we found that H 2 was formed efficiently on the DLC even at 20 K, which is higher than the threshold for H 2 formation on ASW. However, the formation at 20…”

Section: Hydrogen Reactions On Icy Grainsmentioning

confidence: 99%

Radical reactions on interstellar icy dust grains: Experimental investigations of elementary processes

Tsuge

Watanabe

2023

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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“…The REMPI (resonance-enhanced multiphoton ionization [66]) method was initiated by K. Fukutani and its group at Tokyo University to study the H 2 conversion on silver samples in 2003 [41,42]. Later, in 2010, Watanabe et al, Sugimoto and Fukutani observed the o-p conversion of hydrogen adsorbed on amorphous solid water ice (ASW) by a combination of photo-stimulated desorption and "REMPI" methods [65,66,[77][78][79][80][81][82]. Later on, they were able to detect hydrogen conversion on other cosmic dust analogues: polycrystalline ice (PCI), pure solid carbon monoxide, and diamond-like carbon.…”

Section: H 2 Adsorbed On Solid Watermentioning

confidence: 99%

“…The physicochemical processes of hydrogen on cosmic dust, such as the diffusion of H atoms and nuclear spin conversion of H 2 molecules at low temperatures, have a significant influence on the subsequent chemical evolution in space [50,[77][78][79][80][81][82]. The birthplace of stars and planets, namely, the interstellar cloud consisting of gaseous species and cosmic silicate dust, are the starting point of chemical evolution in space, where most of the relatively light elements, such as hydrogen, carbon, oxygen, and nitrogen, first exist as atoms.…”

Section: H 2 Adsorbed On Solid Watermentioning

confidence: 99%

Hydrogen Conversion in Nanocages

Ilisca

2021

Hydrogen

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Hydrogen molecules exist in the form of two distinct isomers that can be interconverted by physical catalysis. These ortho and para forms have different thermodynamical properties. Over the last century, the catalysts developed to convert hydrogen from one form to another, in laboratories and industries, were magnetic and the interpretations relied on magnetic dipolar interactions. The variety concentration of a sample and the conversion rates induced by a catalytic action were mostly measured by thermal methods related to the diffusion of the o-p reaction heat. At the turning of the new century, the nature of the studied catalysts and the type of measures and motivations completely changed. Catalysts investigated now are non-magnetic and new spectroscopic measurements have been developed. After a fast survey of the past studies, the review details the spectroscopic methods, emphasizing their originalities, performances and refinements: how Infra-Red measurements characterize the catalytic sites and follow the conversion in real-time, Ultra-Violet irradiations explore the electronic nature of the reaction and hyper-frequencies driving the nuclear spins. The new catalysts, metallic or insulating, are detailed to display the operating electronic structure. New electromagnetic mechanisms, involving energy and momenta transfers, are discovered providing a classification frame for the newly observed reactions.

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“…This PSD-REMPI method has been successfully applied for detecting atomic and molecular hydrogen on analogues of astronomical dust surfaces, 17−22 and the experimental outcomes are summarized in a recent review paper. 23 In this account, we introduce the application of the PSD-REMPI method for the detection of OH radicals on ASW surfaces (section 2). 1 In section 3, the electrondriven chemistry of OH radicals on ASW, as demonstrated from the observation of a negative charge current, will be overviewed, 2,3 and a future outlook will be given in section 4.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, our group developed a new method to sensitively detect surface adsorbates with a combination of photostimulated desorption (PSD) and resonance-enhanced multiphoton ionization (REMPI) techniques. This PSD-REMPI method has been successfully applied for detecting atomic and molecular hydrogen on analogues of astronomical dust surfaces, − and the experimental outcomes are summarized in a recent review paper . In this account, we introduce the application of the PSD-REMPI method for the detection of OH radicals on ASW surfaces (section ).…”

Section: Introductionmentioning

confidence: 99%

Behavior of Hydroxyl Radicals on Water Ice at Low Temperatures

Tsuge

Watanabe

2021

Acc. Chem. Res.

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Because chemical reactions on/in cosmic ice dust grains covered by amorphous solid water (ASW) play important roles in generating a variety of molecules, many experimental and theoretical studies have focused on the chemical processes occurring on the ASW surface.In laboratory experiments, conventional spectroscopic and mass-spectrometric detection of stable products is generally employed to deduce reaction channels and mechanisms. However, despite their importance, the details of chemical reactions involving reactive species (i.e., free radicals) have not been clarified because of the absence of experimental methods for in situ detection of radicals. Because OH radicals can be easily produced in interstellar conditions by not only the photolysis and/or ion bombardments of H2O but also the reaction of H and O atoms, they are thought to be one of the most abundant radicals on ice dust. In this context, the development of a close monitoring method of OH radicals on the ASW surface may help to elucidate the chemical reactions occurring on the ASW surface.Recently, to detect OH radicals adsorbed on the ASW surface, we applied our developed method to sensitively and selectively detect surface adsorbates with a combination of photostimulated desorption and resonance-enhanced multiphoton ionization techniques.Using this method, we showed that an OH radical on the ASW surface can be desorbed upon one-photon absorption at 532 nm, at which wavelength both the OH radical and H2O molecule are transparent. Theoretical calculations addressing an OH radical adsorbed on water clusters indicated that the valence A-X transition of an OH radical significantly redshifts by ~2 eV when the OH radical is strongly adsorbed to ice through three hydrogen bonds.With this method, the number density of surface OH can be monitored as a snapshot so that the behaviors of OH radicals, such as surface diffusion, can be studied. Moreover, the development of a system for studying the wavelength dependence of photodesorption may establish a foundation for future research investigating the absorption spectra of surface adsorbed species.

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Experimental Approach to Physicochemical Hydrogen Processes on Cosmic Ice Dust

Cited by 6 publications

References 99 publications

Radical reactions on interstellar icy dust grains: Experimental investigations of elementary processes

Radical reactions on interstellar icy dust grains: Experimental investigations of elementary processes

Hydrogen Conversion in Nanocages

Behavior of Hydroxyl Radicals on Water Ice at Low Temperatures

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