Lyman-alpha line
Sign in to savethumb|upright|The All-sky New Horizons Alice Lyα maps in ecliptic coordinates centered on the anti-Sun direction, and the lower map is in Galactic coordinates. The c. 90,000 stars in the M. A. Velez et al. (2024) catalog are overlaid as black dots, where the size of the dot is proportional to the logarithm of the expected Alice count rate from each star. The map in Galactic coordinates indicates the outlines of four of the important LISM clouds ("LIC", in red; "Aql" in green; "Blue", in blue; and "G", in tan). Lyman-alpha, typically denoted by Ly-α or Lyα, is a spectral line of hydrogen (
Article
4 sectionsContents
- Fine structure
- Observation
- See also
- References
thumb|upright|The All-sky New Horizons Alice Lyα maps in ecliptic coordinates centered on the anti-Sun direction, and the lower map is in Galactic coordinates. The c. 90,000 stars in the M. A. Velez et al. (2024) catalog are overlaid as black dots, where the size of the dot is proportional to the logarithm of the expected Alice count rate from each star. The map in Galactic coordinates indicates the outlines of four of the important LISM clouds ("LIC", in red; "Aql" in green; "Blue", in blue; and "G", in tan). Lyman-alpha, typically denoted by Ly-α or Lyα, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series. A photon is emitted when the atomic electron transitions from an n = 2 orbital to the ground state (n = 1), where n is the principal quantum number. In hydrogen, its wavelength of 1215.67 angstroms ( or ), corresponding to a frequency of about , places Lyman-alpha in the ultraviolet (UV) part of the electromagnetic spectrum. More specifically, Ly-α lies in vacuum UV (VUV), characterized by a strong absorption in the air.
==Fine structure== thumb|The Lyman-alpha doublet. Because of the spin–orbit interaction, the Lyman-alpha line splits into a fine-structure doublet with the wavelengths of 1215.668 and 1215.674 angstroms. These components are called Ly-α3/2 and Ly-α1/2, respectively.