An Etymological Dictionary of Astronomy and Astrophysics

A series of → spectral lines in the → infrared spectrum of → neutral hydrogen emitted by electrons in → excited states transitioning to the level described by the → principal quantum number  n = 6. It begins at 12368 nm (Hu α 12.37 microns) and has been traced to 3281.4 nm (3.28 microns).

See also: Named after Curtis J. Humphreys (1898-1986), American physicist; → series.