- Lyman-alpha line
physics, the Lyman-alpha line is a spectral lineof hydrogen, or more generally of one-electron ions, in the Lyman series, emitted when the electronfalls from the orbital to the orbital, where "n" is the principal quantum number. In hydrogen, its wavelengthof 121.6 nanometres, corresponding to a frequencyof 2.47 × 1015 hertz, places the Lyman-alpha line in the far ultravioletpart of the electromagnetic spectrum.
fine structureperturbations, the Lyman-alpha line splits into a doublet. Specifically, because of the electron's spin-orbit interaction, the stationary eigenstates of the perturbed Hamiltonianmust be labeled by the "total" angular momentum "j" of the electron (spin plus orbital), not just the orbital angular momentum . In the orbital, there are two possible states, and , resulting in a spectral doublet. The state is of higher energy (less negative) and so is energetically farther from the orbital to which it is transitioning. Thus, the state is associated with the more energetic (shorter wavelength) spectral line in the doublet.
A K-alpha or Kα line analogous to the Lyman-alpha line for hydrogen, occur in the high-energy induced emission spectra of all chemical elements, since it results from the same electron transition as in hydrogen. The equation for prediction of the frequency of this line (usually in the X-ray range for heavier elements), uses the same base-frequency as Lyman-alpha, but modified by a (Z-1)² factor to account for differing atomic numbers (Z) between elements, and is expressed as
Moseley's law. The Lyman-alpha line and the rest of the hydrogen Lyman spectral series are most simply described by the empiric Rydberg equationand semi-classic Bohr modelof the atom.
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