# Low temperature rates for key steps of interstellar gas-phase water formation.
> 星間ガス相における水分子形成の低温反応速度定数の測定


## Abstract

Water molecule formation in the diffuse interstellar medium (ISM) proceeds through sequential reactions involving molecular ions such as OH, HO, and HO together with molecular hydrogen. These reaction networks also underpin the synthesis of more complex molecular species in space. Rate coefficients for two critical steps in this pathway were experimentally determined at temperatures below 100 K (spanning 10–100 K). The measured values were substantially larger than those currently adopted in standard astronomical models. Theoretical calculations employing a ring-polymer molecular dynamics framework, which provides a first-principles description of low-temperature barrierless reactions, showed strong agreement with the experimental data. These findings suggest that existing astrochemical models may require revision of the rate parameters used for interstellar water chemistry.

### Mechanism

Ring-polymer molecular dynamics calculations provided a first-principles treatment of barrierless gas-phase reactions, yielding rate coefficients at 10–100 K that substantially exceed values used in prior astrochemical models.

## Bibliographic

- **Authors**: Kumar SS, Grussie F, Suleimanov YV, Guo H, Kreckel H
- **Journal**: Sci Adv
- **Year**: 2018
- **PMID**: [29942857](https://pubmed.ncbi.nlm.nih.gov/29942857/)
- **DOI**: [10.1126/sciadv.aar3417](https://doi.org/10.1126/sciadv.aar3417)
- **PMC**: [PMC6014714](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014714/)
- **Study type**: other
- **Delivery route**: not specified
- **Effect reported**: not assessed

## Delivery context

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)

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> **Cite as**: H2 Papers — PMID 29942857. https://h2-papers.org/en/papers/29942857
> **Source**: PubMed PMID [29942857](https://pubmed.ncbi.nlm.nih.gov/29942857/)