A sequence of absorption or emission lines in the near-infrared part of the spectrum, due to hydrogen. They are caused by electron jumps between the third energy level and higher levels. The Paschen-α line has a wavelength of 1875 nm, and the spacing between the lines diminishes as they converge on the series limit at 820 nm. The series is named after the German physicist (Louis Carl Heinrich) Friedrich Paschen (1865–1947). See also hydrogen spectrum.
Subjects: Astronomy and Astrophysics.