H, He-like recombination spectra VI: Quadrupole $l$-changing collisions
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arXiv
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| Autori principali: | , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866909572643422208 |
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| author | Deliporanidou, E. Badnell, N. R. Storey, P. J. Del Zanna, G. Ferland, G. J. |
| author_facet | Deliporanidou, E. Badnell, N. R. Storey, P. J. Del Zanna, G. Ferland, G. J. |
| contents | We have developed a simple analytic formula that well describes quadrupole $l$-changing collisions of the form $nl \rightarrow nl'$, as confirmed by comparison with numerical quantal Born calculations obtained with the program autostructure (Badnell 2011). Such formulae could easily be included in models of astrophysical plasma emission, such as the hydrogen and helium-like recombination spectra. When compared with the results of previous quantal calculations based upon an analytic solution of the time-dependent Schrödinger equation by Vrinceanu & Flannery (2001), we find relatively good agreement, with the exception of large $l > n/2$ transitions. We provide a tentative explanation for such discrepancies. However, we also show that the rates for quadrupole $l$-changing collisions are typically two orders of magnitude lower than the dipolar ones. Inclusion of the quadrupolar rates in a hydrogenic collisional-radiative model of nebular plasma shows minimal changes to the level populations, typically within 1% in nebular conditions. Simple and complete theories are now available for $l$-changing collisions suitable for astrophysical applications. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_03570 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | H, He-like recombination spectra VI: Quadrupole $l$-changing collisions Deliporanidou, E. Badnell, N. R. Storey, P. J. Del Zanna, G. Ferland, G. J. Atomic Physics Astrophysics of Galaxies High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Plasma Physics We have developed a simple analytic formula that well describes quadrupole $l$-changing collisions of the form $nl \rightarrow nl'$, as confirmed by comparison with numerical quantal Born calculations obtained with the program autostructure (Badnell 2011). Such formulae could easily be included in models of astrophysical plasma emission, such as the hydrogen and helium-like recombination spectra. When compared with the results of previous quantal calculations based upon an analytic solution of the time-dependent Schrödinger equation by Vrinceanu & Flannery (2001), we find relatively good agreement, with the exception of large $l > n/2$ transitions. We provide a tentative explanation for such discrepancies. However, we also show that the rates for quadrupole $l$-changing collisions are typically two orders of magnitude lower than the dipolar ones. Inclusion of the quadrupolar rates in a hydrogenic collisional-radiative model of nebular plasma shows minimal changes to the level populations, typically within 1% in nebular conditions. Simple and complete theories are now available for $l$-changing collisions suitable for astrophysical applications. |
| title | H, He-like recombination spectra VI: Quadrupole $l$-changing collisions |
| topic | Atomic Physics Astrophysics of Galaxies High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Plasma Physics |
| url | https://arxiv.org/abs/2504.03570 |