# Spin-Conserved and Spin-Flip Optical Excitations from the Bethe-Salpeter Equation Formalism.
> ベーテ・サルピーター方程式形式論におけるスピン保存およびスピンフリップ光学励起


## Abstract

This paper belongs to the domain of quantum chemistry and many-body perturbation theory, with no relevance to biomedical hydrogen research. The authors extend the Bethe-Salpeter equation (BSE) formalism by incorporating a spin-flip approach, using the lowest triplet state as the reference configuration rather than the singlet ground state, to access double and higher excitations that are inaccessible in the standard static approximation. A spin-unrestricted GW scheme is employed to compute charged excitations and the screened Coulomb potential. Dynamical corrections are introduced via an unrestricted perturbative treatment. Benchmark calculations are performed on the beryllium atom, the H2 molecule at multiple bond lengths, and cyclobutadiene in rectangular and square-planar geometries. No biological, physiological, or medical content is present.

## Bibliographic

- **Authors**: Monino E, Loos PF
- **Journal**: J Chem Theory Comput
- **Year**: 2021 (2021-05-11)
- **PMID**: [33724811](https://pubmed.ncbi.nlm.nih.gov/33724811/)
- **DOI**: [10.1021/acs.jctc.1c00074](https://doi.org/10.1021/acs.jctc.1c00074)
- **PMC**: [PMC8154368](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8154368/)
- **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 33724811. https://h2-papers.org/en/papers/33724811
> **Source**: PubMed PMID [33724811](https://pubmed.ncbi.nlm.nih.gov/33724811/)