Non-quadrupole lines in X-ray spectra

Abstract

IT is well known that, by giving prolonged exposures, many forbidden lines appear in X-ray emission spectra violating the dipole selection rules derived from theory. Most of the forbidden lines obey the quadrupole selection rules, namely, δl = 0, ± 1, ± 2 and δj = 0, ± 1, ± 2, except l = 0 to l = 0, and j = 0 to j = 0 and j = ½ to j = ½. Some workers have, however, noticed a few forbidden lines which even violate the quadrupole selection rules and which cannot be explained by any multipole radiation theory. Such lines are generally known as 'non-quadrupole' lines.