The Paschen series is the series of transitions and resulting emission lines of the hydrogen atom as an electron goes from n ≥ 4 to n = 3 (where n refers to the energy level of the electron). The transitions are named sequentially by Greek letter: n = 4 to n = 3 is called Paschen-alpha, 5 to 3 is Paschen-beta, 6 to 3 is Paschen-gamma, etc.

They are named for the Austro-German physicist Friedrich Paschen.

See also: Bohr model, Rydberg formula, H-alpha, Balmer series, Lyman series