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| The '''Wolf |
The '''Wolf effect''' (sometimes '''Wolf shift''') is a ] shift in the ].<ref>Emil Wolf, "" (2001) , {{ISBN|981-02-4204-2}}.</ref> | ||
| The phenomenon occurs in several closely related phenomena in ], with analogous effects occurring in the ] of light.<ref name="james">James |
The phenomenon occurs in several closely related phenomena in ], with analogous effects occurring in the ] of light.<ref name="james">{{cite journal | last=James | first=Daniel F V | title=The Wolf effect and the redshift of quasars | journal=Pure and Applied Optics: Journal of the European Optical Society Part A | publisher=IOP Publishing | volume=7 | issue=5 | year=1998 | issn=0963-9659 | doi=10.1088/0963-9659/7/5/006 | pages=959–970|arxiv=astro-ph/9807205| bibcode=1998PApOp...7..959J | s2cid=17670250 }}</ref> It was first predicted by ] in 1987<ref name="wolf87nature">{{cite journal | last=Wolf | first=Emil | title=Non-cosmological redshifts of spectral lines | journal=Nature | publisher=Springer Science and Business Media LLC | volume=326 | issue=6111 | year=1987 | issn=0028-0836 | doi=10.1038/326363a0 | pages=363–365| bibcode=1987Natur.326..363W | s2cid=4337925 }}</ref><ref>{{cite journal | last=Wolf | first=Emil | title=Redshifts and blueshifts of spectral lines caused by source correlations | journal=Optics Communications | publisher=Elsevier BV | volume=62 | issue=1 | year=1987 | issn=0030-4018 | doi=10.1016/0030-4018(87)90057-5 | pages=12–16| bibcode=1987OptCo..62...12W | doi-access=free }}</ref> and subsequently confirmed in the laboratory in acoustic sources by Mark F. Bocko, ], and Robert S. Knox,<ref>{{cite journal | last1=Bocko | first1=Mark F. | last2=Douglass | first2=David H. | last3=Knox | first3=Robert S. | title=Observation of frequency shifts of spectral lines due to source correlations | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=58 | issue=25 | date=1987-06-22 | issn=0031-9007 | doi=10.1103/physrevlett.58.2649 | pages=2649–2651| pmid=10034809 | bibcode=1987PhRvL..58.2649B }}</ref> and a year later in optic sources by Dean Faklis and George Morris in 1988.<ref>{{cite journal | last1=Faklis | first1=Dean | last2=Morris | first2=G. Michael | title=Spectral shifts produced by source correlations | journal=Optics Letters | publisher=The Optical Society | volume=13 | issue=1 | date=1988-01-01 | issn=0146-9592 | doi=10.1364/ol.13.000004 | page=4—6| pmid=19741961 | bibcode=1988OptL...13....4F }}</ref> | ||
| :"Under certain conditions the changes in the spectrum of light scattered on random media may imitate the ], even though the source, the medium and the observer are all at rest with respect to one another.<ref name="wolf96james">Wolf, Emil, and James, Daniel F. V., "" (1996) ''Reports on Progress in Physics'' 59: 771—818. (, PDF)</ref> | |||
| Wolf, Daniel James and Sisir Roy ''et al.'' suggested that the Wolf Effect may explain ] in certain quasars <ref>Roy, Sisir, Kafatos, Menas, and Datta, Suman, "" (2000) ''Astronomy and Astrophysics'', v.353, p.1134-1138 353: 1134—1138.</ref><ref name="wolf87nature" /><ref name="james" /> in reference to the historical controversies surrounding the nature of ]s that were resolved after the ]. | |||
| ==Theoretical description== | ==Theoretical description== | ||
| ⚫ | In ], two non-] sources that emit beamed energy can interact in a way that causes a shift in the spectral lines. It is analogous to a pair of tuning forks with similar frequencies (pitches), connected together mechanically with a sounding board; there is a strong coupling that results in the resonant frequencies getting "dragged down" in pitch. The Wolf Effect requires that the waves from the sources are partially ] - the wavefronts being partially in phase. ] light is coherent while candlelight is incoherent, each photon having random phase. It can produce either redshifts or blueshifts, depending on the observer's point of view, but is redshifted when the observer is head-on.<ref name="wolf87nature" /> | ||
| ⚫ | For two sources interacting while separated by a vacuum, the Wolf effect cannot produce shifts greater than the ] of the source ], since it is a position-dependent change in the distribution of the source spectrum, not a method by which new frequencies may be generated. However, when interacting with a medium, in combination with effects such as ] it may produce distorted shifts greater than the linewidth of the source. | ||
| ⚫ | In ], |
||
| ⚫ | For two sources interacting while separated by a vacuum, the Wolf effect cannot produce shifts greater than the ] of the source ], since it is a position-dependent change in the distribution of the source spectrum, not a method by which new frequencies may be generated. However, when interacting with a medium, in combination with effects such as ] it may produce distorted shifts greater than the linewidth of the source |
||
| An example of such a medium which could produce Doppler-like shifts was found in 1990 by Daniel James, Malcolm Savedoff, Malcolm and Emil Wolf,<ref>James, Daniel F. V., Savedoff, Malcolm P., and Wolf, Emil, "" (1990) ''Astrophysical Journal'' 359: 67—71. (, PDF)</ref> and involved a highly ''statistically ]'' scattering medium. A "no blueshift" condition has also been found by Datta, S. ''et al.'', <ref>Datta, S., Roy, S., Roy, M., and Moles, M., "" (1998) ''Physical Review A'' 58 (1): 720—723.</ref> <ref>Roy, S., Kafatos, M., and Datta, S., " (1999) astro-ph/9904061</ref>. | |||
| Wolf and James noted <ref name="wolf96james" /> that: | |||
| :"Although we make no claim that correlation-induced spectral shifts account for all, or even for a majority, of the observed shifts of lines in the spectra of extra-galactic objects, we note the possibility that correlation-induced spectral shifts may contribute to the shifts observed in the spectra of some astronomical objects such as quasars." | |||
| James also noted that <ref name="james" /> that: | |||
| :"One can easily spot potential problems with the theory presented here. For example, we have been deliberately vague about the underlying physical nature of the scattering medium, other than specifying its anisotropic coherence properties. The scatterer, which is assumed to have a ‘white noise’ power spectrum (implying that its fluctuations are very energetic), is situated further away from the central engine than the line emitting clouds (which cannot be too hot, otherwise they would have completely ionized, making line radiation impossible). Although our results apply for a broad spectral range, we have not considered the shifts of absorption lines or of the 21cm radio line. We have ignored the unscattered radiation and the efficiency of the scattering process (although it is possible a stimulated version of the spontaneous scattering process considered here is applicable). Also the issue of spectral linewidths has not been addressed." | |||
| ==Notes== | ==Notes== | ||
| <div style="font-size: 95%"> | <div style="font-size: 95%"> | ||
| {{Reflist}} | |||
| <!--See ] for an explanation of how to generate footnotes using the <ref(erences/)> tags--> | |||
| <references/> | |||
| </div> | </div> | ||
| ==See also== | |||
| * ] | |||
| ] | ] | ||
| ] | ] | ||
| {{scattering-stub}} | |||
| {{spectroscopy-stub}} | |||
Latest revision as of 05:52, 11 December 2023
The Wolf effect (sometimes Wolf shift) is a frequency shift in the electromagnetic spectrum. The phenomenon occurs in several closely related phenomena in radiation physics, with analogous effects occurring in the scattering of light. It was first predicted by Emil Wolf in 1987 and subsequently confirmed in the laboratory in acoustic sources by Mark F. Bocko, David H. Douglass, and Robert S. Knox, and a year later in optic sources by Dean Faklis and George Morris in 1988.
Theoretical description
In optics, two non-Lambertian sources that emit beamed energy can interact in a way that causes a shift in the spectral lines. It is analogous to a pair of tuning forks with similar frequencies (pitches), connected together mechanically with a sounding board; there is a strong coupling that results in the resonant frequencies getting "dragged down" in pitch. The Wolf Effect requires that the waves from the sources are partially coherent - the wavefronts being partially in phase. Laser light is coherent while candlelight is incoherent, each photon having random phase. It can produce either redshifts or blueshifts, depending on the observer's point of view, but is redshifted when the observer is head-on.
For two sources interacting while separated by a vacuum, the Wolf effect cannot produce shifts greater than the linewidth of the source spectral line, since it is a position-dependent change in the distribution of the source spectrum, not a method by which new frequencies may be generated. However, when interacting with a medium, in combination with effects such as Brillouin scattering it may produce distorted shifts greater than the linewidth of the source.
Notes
- Emil Wolf, "Selected Works of Emil Wolf: With Commentary" (2001) p.638, ISBN 981-02-4204-2.
- James, Daniel F V (1998). "The Wolf effect and the redshift of quasars". Pure and Applied Optics: Journal of the European Optical Society Part A. 7 (5). IOP Publishing: 959–970. arXiv:astro-ph/9807205. Bibcode:1998PApOp...7..959J. doi:10.1088/0963-9659/7/5/006. ISSN 0963-9659. S2CID 17670250.
- ^ Wolf, Emil (1987). "Non-cosmological redshifts of spectral lines". Nature. 326 (6111). Springer Science and Business Media LLC: 363–365. Bibcode:1987Natur.326..363W. doi:10.1038/326363a0. ISSN 0028-0836. S2CID 4337925.
- Wolf, Emil (1987). "Redshifts and blueshifts of spectral lines caused by source correlations". Optics Communications. 62 (1). Elsevier BV: 12–16. Bibcode:1987OptCo..62...12W. doi:10.1016/0030-4018(87)90057-5. ISSN 0030-4018.
- Bocko, Mark F.; Douglass, David H.; Knox, Robert S. (1987-06-22). "Observation of frequency shifts of spectral lines due to source correlations". Physical Review Letters. 58 (25). American Physical Society (APS): 2649–2651. Bibcode:1987PhRvL..58.2649B. doi:10.1103/physrevlett.58.2649. ISSN 0031-9007. PMID 10034809.
- Faklis, Dean; Morris, G. Michael (1988-01-01). "Spectral shifts produced by source correlations". Optics Letters. 13 (1). The Optical Society: 4—6. Bibcode:1988OptL...13....4F. doi:10.1364/ol.13.000004. ISSN 0146-9592. PMID 19741961.
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