O. Hemmers et al., Relativistic effects on interchannel coupling in atomic photoionization: The photoelectron angular distribution of Xe 5s - art. no. 022507, PHYS REV A, 6402(2), 2001, pp. 2507
Measurements of the photoelectron angular-distribution asymmetry parameter
beta for Xe 5s photoionization have been performed in the 80-200 eV photon-
energy region. The results show a substantial deviation from the nonrelativ
istic value of beta = 2 and provide a clear signature of significant relati
vistic effects in interchannel coupling.