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free-free absorptionA process of absorption that occurs when a free electron absorbs a photon of radiation and moves to a higher energy state: the difference between final and initial electron energy is equal to the photon energy. See also opacity.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
free-free absorption[′frē ′frē ab′sȯrp·shən]
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.