quantum defect
Also found in: Wikipedia.
quantum defect
[′kwän·təm ′dē‚fekt] (atomic physics)
The difference between the principal quantum number of an atomic energy level and the effective quantum number obtained by fitting with a Rydberg formula the energy required to ionize the atom from that level.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.