Hyperfine Structure of the Quadrupole Line 2815A and of Some Other Lines of Ionized Mercury

The structure of many lines of ionized mercury is investigated by means of apparatus of high resolving power. Most of them have been found to possess complex structure. The components of the lines 2815, 3984 and 2848A are measured and the structure analyzed in terms of isotope shift and hyperfine structure. It is shown that in the case of a forbidden line of quadrupole character like the line 2815A the intensities of the hyperfine components must be computed from the formulas given by Rubinowicz (replacing $J,L$ and $S$ by $F,J$ and $I$). The hyperfine structure splittings of the levels $6s^2{S}_{\frac{1}{2}}$, $5d^{9}6s^2{}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}$ and $6p^2{P}_{\frac{3}{2}}$ found experimentally are in agreement with Goudsmit's formulas and allow in the case of the $6s^2{S}_{\frac{1}{2}}$ level a very accurate evaluation of the nuclear $g$ factors for the isotope 199. The isotopic shifts in Hg II levels are discussed.