An Etymological Dictionary of Astronomy and Astrophysics
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A sequence of → permitted transitions in the → ultraviolet from an → excited state (B) of the → molecular hydrogen (H₂) to the electronic → ground state, with ΔE > 11.2 eV, λ < 1108Å (first → band head). When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (B). The following rapid → decay creates an → absorption band in that wavelength range. See also → Werner band. → Lyman-Werner photon.

→ Lyman (Th. Lyman, 1906, Astrophys. J. 23, 181); → band.