Hyperfine structure in the 5 d 96 p and 5 d 86 s 2configurations of the spectrum of Hg III

In most of the lines 5d9 6p–5d8682 the components due to 200Hg, 202Hg and 204Hg have been resolved and term isotope shifts have been assigned for these isotopes for nearly all the terms of each configuration. Some less accurate data for 198Hg, 199Hg and 201Hg are obtained from measurements on incompletely resolved components. An approximate magnetic hfs analysis for all terms of 5d9 6p and 5d8 682 has been made for 199Hg. This analysis was made on the assumption that components of even isotopes always preserve the same relative spacing. The assumption does not appear to be strictly valid in a few cases, the largest departure apparently occurring in lines measured by Mrozowski (1942) involving the 5d8½ ½ 682|0 term (and possibly in two other lines). The magnetic hfs is compared with that expected for jj-coupling, and it conforms moderately well, but there is evidence of intermediate coupling effects in both configurations, especially 5d9 6p, and in one term at least of this configuration there is also indication of a small perturbation from 5d8 68 6p. By deducing the nuclear magnetic moment of 199Hg the results are shown to be tolerably consistent with previous investigations. The isotopic structures are very regular compared with those reported for the isoelectronic Pt I spectrum. Such small irregularities as have been found are discussed; those found in 5d8 682 do not seem to be due to the nuclear ‘volume’ effect.