Balmer lines (Balmer series)
A series of spectral lines in the spectrum of atomic hydrogen. The lines are termed H alpha, H beta, H gamma, and so on, starting with the line of longest wavelength, which is at 656.3 nanometres. The lines become more closely spaced with decreasing wavelength, merging at the series limit of 365 nanometres.

See also: Balmer decrement.