Zeeman effect

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The splitting of single spectral lines of an emission spectrum into three or more polarized components when the radiation source is in a magnetic field.

from The Century Dictionary.

• noun See effect.

from the GNU version of the Collaborative International Dictionary of English.

• (Physics) The widening and duplication, triplication, etc., of spectral lines when the radiations emanate in a strong magnetic field, first observed in 1896 by P. Zeeman, a Dutch physicist, and regarded as an important confirmation of the electromagnetic theory of light.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics the splitting of single spectral lines into three (or more) in the presence of a magnetic field