the dividing of a spectral line or lines as a result of placing a radiation source in a magnetic field. The division consists of three equally spaced lines (normal Zeeman effect) in systems for which the spin quantum number is zero, or of three or more unequally spaced lines (anomalous Zeeman effect) in systems for which the spin quantum number is not zero. Also called Zee'man split"ting. Cf. Paschen-Back effect.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.