Reflection spectrum

Not to be confused with Reflectance spectrum.

In physics, a reflection spectrum is the spectrum of reflected light emitted from an object or material. The properties of the reflecting material affect its reflection spectrum, allowing for chemical analysis of the substance. Reflection spectra can also provide information about the original light source.[1] Reflection spectroscopy has applications in astronomy and materials science.

Astronomy

Exoplanetology

The atmospheres of exoplanets reflect light from their host stars, and these reflection spectra can be used to determine the atmospheric composition of a planet.[2] Different elements and compounds reflect light differently, and astronomers can use spectroscopy to determine the peak frequencies at which light is reflected and therefore what compounds are doing the reflecting.[3] It may also be possible to use reflection spectra to observe the surface composition of terrestrial planets; this would also confirm experimentally that the planet is terrestrial.[4] Reflection spectra can also reveal molecules in a planet's atmosphere that are commonly associated with or created by life, providing evidence that an exoplanet may host life.[5]

High-energy astrophysics

Accretion disks of black holes and neutron stars frequently show a spectrum associated with the reflection of light from an irradiating source; this source is generally believed to be a corona surrounding the disk. Accretion disk reflection spectra are generally most prominent in X-ray wavelengths. The spectrum of coronal emission is altered based on properties of the disk and relativistic effects such as gravitational redshift; this phenomenon is known as relativistic reflection. Thus, accretion disk reflection spectra can provide direct information on the structure, temperature, composition, and degree of ionization of the disk, as well as the spin rate of the compact object.[6][1]

Materials science

Reflection spectra can aid in identifying and distinguishing similar materials or compounds, such as different types of oil. When light reflects off of a substance, that substance's chemical properties directly affect the spectrum of light reflected off of that substance. This can be used to identify compounds that may be difficult to distinguish otherwise, particularly in machine-learning algorithms that identify different compounds by spectrum.[7] Reflection spectra can also be used to identify properties of compounds, such as refraction index, polarity, and viscosity.[8] Factors that can affect a material's reflection spectrum include temperature,[9] particle size,[10] and presence (or absence) of a magnetic field.[11]

References

  1. ^ a b Feng, Yuan; Yuan, Ye-Fei; Zhang, Shuang-Nan (2025). "Reflection Spectra of Accretion Disks Illuminated by an Off-axis Corona". The Astrophysical Journal. 984 (2): 173. doi:10.3847/1538-4357/adc8a6.
  2. ^ Kitzmann, D.; Patzer, A. B. C.; von Paris, P.; Godolt, M.; Rauer, H. (2011). "Clouds in the atmospheres of extrasolar planets". Astronomy & Astrophysics. 534: A63. doi:10.1051/0004-6361/201117375.
  3. ^ MacDonald, Ryan J.; Marley, Mark S.; Fortney, Jonathan J.; Lewis, Nikole K. (2018). "Exploring H2O Prominence in Reflection Spectra of Cool Giant Planets". The Astrophysical Journal. 858 (2): 69. doi:10.3847/1538-4357/aabb05.
  4. ^ Hu, Renyu; Ehlmann, Bethany L.; Seager, Sara (2012). "Theoretical Spectra of Terrestrial Exoplanet Surfaces". The Astrophysical Journal. 752: 7. doi:10.1088/0004-637X/752/1/7.
  5. ^ Madden, Jack; Kaltenegger, Lisa (2020). "High-resolution Spectra for a Wide Range of Habitable Zone Planets around Sun-like Stars". The Astrophysical Journal Letters. 898 (2): L42. doi:10.3847/2041-8213/aba535.
  6. ^ García, J.; Dauser, T.; Reynolds, C. S.; Kallman, T. R.; McClintock, J. E.; Wilms, J.; Eikmann, W. (2013). "X-Ray Reflected Spectra from Accretion Disk Models. III. A Complete Grid of Ionized Reflection Calculations". The Astrophysical Journal. 768 (2): 146. doi:10.1088/0004-637X/768/2/146.
  7. ^ Xie, Ming; Dong, Shuang; Gou, Tao; Li, Ying; Han, Bing (2023). "Evaluation and optimization of the three-band spectral indices for oil type identification using reflection spectrum". Journal of Quantitative Spectroscopy and Radiative Transfer. 304 108609. doi:10.1016/j.jqsrt.2023.108609.
  8. ^ Zhang, Yuqi; Fu, Qianqian; Ge, Jianping (2015). "Photonic sensing of organic solvents through geometric study of dynamic reflection spectrum". Nature Communications. 6 7510. doi:10.1038/ncomms8510. PMC 4557364. PMID 26082186.
  9. ^ Suto, H.; Sogawa, H.; Tachibana, S.; Koike, C.; Karoji, H.; Tsuchiyama, A.; Chihara, H.; Mizutani, K.; Akedo, J.; Ogiso, K.; Fukui, T.; Ohara, S. (2006). "Low-temperature single crystal reflection spectra of forsterite". Monthly Notices of the Royal Astronomical Society. 370 (4): 1599–1606. doi:10.1111/j.1365-2966.2006.10594.x.
  10. ^ Udvardi, Beatrix; Kovács, István J.; Fancsik, Tamás; Kónya, Péter; Bátori, Miklósné; Stercel, Ferenc; Falus, György; Szalai, Zoltán (2017). "Effects of Particle Size on the Attenuated Total Reflection Spectrum of Minerals". Applied Spectroscopy. 71 (6): 1157–1168. doi:10.1177/0003702816670914. PMID 27671141.
  11. ^ Shimoda, Y.; Ozaki, M.; Yoshino, K. (2001). "Electric field tuning of a stop band in a reflection spectrum of synthetic opal infiltrated with nematic liquid crystal". Applied Physics Letters. 79 (22): 3627–3629. doi:10.1063/1.1421080.

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