# High-resolution millimeter wave spectroscopy and multichannel quantum defect theory of the hyperfine structure in high Rydberg states of molecular hydrogen H2.
> 分子水素H2の高リドベルク状態における超微細構造の高分解能ミリ波分光と多チャンネル量子欠陥理論


## Abstract

This study developed experimental and theoretical approaches combining high-resolution millimeter-wave spectroscopy with multichannel quantum defect theory (MQDT) to characterize the hyperfine structure of molecular hydrogen H2 in high Rydberg states. Measurements were performed for l=0–3 Rydberg states in the principal quantum number range n=50–65 at sub-MHz resolution. The np1(1), nd1(1), and nf1(0–3) series exhibited metastable lifetimes exceeding 5 µs beyond n=50. Hyperfine structure was found to depend strongly on orbital angular momentum l: exchange interaction dominates in penetrating s and p states, while hyperfine coupling prevails in d and f states, producing mixed singlet-triplet character. MQDT was extended to incorporate hyperfine interactions via a frame transformation between Born-Oppenheimer and asymptotic coupling schemes. Agreement between theory and experiment was achieved to within 600 kHz after adjustment of quantum defect functions. The extrapolated ionic hyperfine structure was consistent with prior ab initio predictions within experimental error.

## Bibliographic

- **Authors**: Osterwalder A, Wüest A, Merkt F, Jungen Ch
- **Journal**: J Chem Phys
- **Year**: 2004 (2004-12-15)
- **PMID**: [15634145](https://pubmed.ncbi.nlm.nih.gov/15634145/)
- **DOI**: [10.1063/1.1792596](https://doi.org/10.1063/1.1792596)
- **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 15634145. https://h2-papers.org/en/papers/15634145
> **Source**: PubMed PMID [15634145](https://pubmed.ncbi.nlm.nih.gov/15634145/)