Lyman-alpha

Common card · No. 445554

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 (121.567 nm or 1.21567×10−7 m), corresponding to a frequency of about 2.46607×1015 Hz, places Lyman-alpha in the ultraviolet (UV) part of the electromagnetic spectrum, with a photon energy of 10.2 eV. More specifically, Ly-α lies in vacuum UV (VUV), characterized by a strong absorption in the air.

Read on Wikipedia · Image G. Randall Gladstone et al, CC BY 4.0