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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2408.01103 |
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| _version_ | 1866908005278154752 |
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| author | Zagury, Frederic |
| author_facet | Zagury, Frederic |
| contents | First identified in 1964, inverse Raman scattering (IRS) is a nonlinear stimulated phenomenon that induces Raman scattered absorptions where Raman emissions would be expected. While IRS is less well-known than stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS), this study highlights its significance in analyzing the spectra of stars located in the distant background of HI interstellar clouds. Specifically, ultraviolet emission lines Raman scattered by atomic hydrogen, typically observed in emission at wide scattering angles in the optical spectra of symbiotic stars and nebulae, should appear as IRS absorption features in the optical spectra of the background stars. I show that all known interstellar Raman scattered emission lines in the H-alpha wavelength region are detected in absorption as diffuse interstellar bands (DIBs) in the spectra of reddened stars, and conclude that IRS by atomic hydrogen resolves the longstanding puzzle of the processes involved in producing these bands, and perhaps also explains the equally mysterious 2200A bump of ultraviolet extinction curves. This identification of DIBs as IRS HI absorptions sheds new light on the perplexing relationship between DIBs and the Red Rectangle nebula emission bands (RRBs).
The conditions under which DIBs are detected highlight the importance of considering the physical relationship between the observer, the HI medium, and the direction of the illuminating radiation field (i.e., the geometry of the observation) in observations of HI interstellar matter. Observing in the direction of the radiation field or on its side determines whether IRS, yielding DIBs and the 2200A bump, or spontaneous Raman scattering at wide scattering angles, resulting in ERE, Raman scattered emission lines (including RRBs), and the unidentified infrared bands, will be observed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2408_01103 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Inverse Raman scattering and the diffuse interstellar bands: an exploration of the systemic interconnections between spontaneous and inverse Raman scattering and extended red emission, Red Rectangle bands, and diffuse interstellar bands Zagury, Frederic Astrophysics of Galaxies First identified in 1964, inverse Raman scattering (IRS) is a nonlinear stimulated phenomenon that induces Raman scattered absorptions where Raman emissions would be expected. While IRS is less well-known than stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS), this study highlights its significance in analyzing the spectra of stars located in the distant background of HI interstellar clouds. Specifically, ultraviolet emission lines Raman scattered by atomic hydrogen, typically observed in emission at wide scattering angles in the optical spectra of symbiotic stars and nebulae, should appear as IRS absorption features in the optical spectra of the background stars. I show that all known interstellar Raman scattered emission lines in the H-alpha wavelength region are detected in absorption as diffuse interstellar bands (DIBs) in the spectra of reddened stars, and conclude that IRS by atomic hydrogen resolves the longstanding puzzle of the processes involved in producing these bands, and perhaps also explains the equally mysterious 2200A bump of ultraviolet extinction curves. This identification of DIBs as IRS HI absorptions sheds new light on the perplexing relationship between DIBs and the Red Rectangle nebula emission bands (RRBs). The conditions under which DIBs are detected highlight the importance of considering the physical relationship between the observer, the HI medium, and the direction of the illuminating radiation field (i.e., the geometry of the observation) in observations of HI interstellar matter. Observing in the direction of the radiation field or on its side determines whether IRS, yielding DIBs and the 2200A bump, or spontaneous Raman scattering at wide scattering angles, resulting in ERE, Raman scattered emission lines (including RRBs), and the unidentified infrared bands, will be observed. |
| title | Inverse Raman scattering and the diffuse interstellar bands: an exploration of the systemic interconnections between spontaneous and inverse Raman scattering and extended red emission, Red Rectangle bands, and diffuse interstellar bands |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2408.01103 |