F' center

F′ center

[¦ef‚prīm ‚sen·tər]
(solid-state physics)
A color center that gives rise to a broad absorption band at longer wavelengths than the band of the F center; probably an F center that has trapped an additional electron.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.