Spectrograms of 208Pb electrodeless discharge tubes operated in a field of 24025 gauss gave Zeeman patterns for fifty-eight PbI spectral transitions from 2189 to 10969 Å and yielded eighteen new g values. There was good agreement between these and the g values predicted by intermediate-coupling eigenvectors determined from least-squares level fitting. The g value of the odd level at 58517 cm?1 indicates that it belongs to the 6p6d configuration instead of 6s6p3 as formerly classified. A striking consequence of configuration interaction has been discovered which results in the total suppression of what would otherwise be a strong line in this spectrum. A predominantly 6p6d level is mixed with 6p7s and interference between the dipole matrix elements connecting respectively the 6d and 7s portions with a ground-state level causes a net dipole moment of almost exactly zero for this transition. However, even in our relatively weak magnetic field, this balance is upset by magnetic mixing of only 0.3% with a third level to enhance the line strength by at least a factor 106! Two related transitions with normal pattern separations display pronounced anomalies in the relative intensities of their Zeeman components. We give a theoretical analysis and quantitative calculations to show that these anomalies are due to combined interference effects of the two types of mixing.
DAVID R. WOOD, KENNETH L. ANDREW, ATHOS GIACCHETTI, and ROBERT D. COWAN, "Zeeman Effect and Intensity Anomalies in PbI," J. Opt. Soc. Am. 58, 830-836 (1968)