Quantum Reorientational Excitations in the Raman Spectrum of Hydrogen
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866918211287515136 |
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| author | Dalladay-Simpson, Philip Edmund, Eric Hu, Huixin Santoro, Mario Gorelli, Federico Aiace |
| author_facet | Dalladay-Simpson, Philip Edmund, Eric Hu, Huixin Santoro, Mario Gorelli, Federico Aiace |
| contents | Low-frequency Raman peaks, below 250 cm-1, are observed in hydrogen between 2-174 GPa and 13-300 K. The origin of these features is attributed to reorientational transitions (DeltaJ = 0; Q0-branch), which shift from the Rayleigh line as anisotropic intermolecular interactions lift the mJ degeneracy. This family of excitations closely follows the behavior of the S0-branches, sharing their dependence on pressure, temperature, and ortho-H2 concentration. Above 65 K, spectra corrected by the Bose-Einstein population factor reveal a broad continuum arising from populated higher J-states and increased ortho-para disorder. Upon entering phase III, where molecular rotation is inhibited, this continuum is quenched, giving way to well-established optical phonons. Below 25 K, equilibrated samples demonstrate a fine structure from isolated and pair excitations from impurity ortho-H2 molecules in a parahydrogen lattice, the latter a sensitive probe to anisotropic intermolecular interactions relevant to the quantum modeling of solid H2. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_16010 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Quantum Reorientational Excitations in the Raman Spectrum of Hydrogen Dalladay-Simpson, Philip Edmund, Eric Hu, Huixin Santoro, Mario Gorelli, Federico Aiace Materials Science Other Condensed Matter Quantum Physics Low-frequency Raman peaks, below 250 cm-1, are observed in hydrogen between 2-174 GPa and 13-300 K. The origin of these features is attributed to reorientational transitions (DeltaJ = 0; Q0-branch), which shift from the Rayleigh line as anisotropic intermolecular interactions lift the mJ degeneracy. This family of excitations closely follows the behavior of the S0-branches, sharing their dependence on pressure, temperature, and ortho-H2 concentration. Above 65 K, spectra corrected by the Bose-Einstein population factor reveal a broad continuum arising from populated higher J-states and increased ortho-para disorder. Upon entering phase III, where molecular rotation is inhibited, this continuum is quenched, giving way to well-established optical phonons. Below 25 K, equilibrated samples demonstrate a fine structure from isolated and pair excitations from impurity ortho-H2 molecules in a parahydrogen lattice, the latter a sensitive probe to anisotropic intermolecular interactions relevant to the quantum modeling of solid H2. |
| title | Quantum Reorientational Excitations in the Raman Spectrum of Hydrogen |
| topic | Materials Science Other Condensed Matter Quantum Physics |
| url | https://arxiv.org/abs/2511.16010 |