Spectrum and energy levels of singly-ionized mercury (Hg II)

The spectrum of singly-ionized mercury (Hg II) has been observed from 500 A to 9880 A with sliding sparks and pulsed-RF discharges on 10.7-m grating spectrographs in vacuum and air. About 500 lines have been classified as transitions between 114 energy levels. In addition to revising the existing system of 5d10nl, 5d96s2, and 5d96s6p energy levels, we have located new levels of the 5d86s26p, 5d96s7p, 5d96s5f, 5d96s7s, 5d96s6d, and 5d96p2 configurations, which occur in the region of the ionization limit. Many of the observed configurations were theoretically interpreted by means of Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels. The fitted parameters were used to calculate oscillator strengths for most of the classified lines. The ionization energy was revised to 151284.4 ± 0.3 cm-1 (18.75687 ± 0.00004 eV). (orig.)