Paschen series

In physics, the Paschen series (also called Ritz-Paschen series) is the series of transitions and resulting emission lines of the principal quantum number 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.