The fourth spectrum of manganese was investigated from 500 to 2500 Å with two-meter normal-incidence vacuum spectrographs. The wavelengths of the spectral lines, excited in both sliding-spark and condensed-spark discharges in helium, were determined with an uncertainty of ±0.006 Å. Forty seven new energy levels belonging to sixteen terms were found and the whole term system was recalculated on the basis of the new measurements. Four hundred and twenty eight spectral lines were classified as transitions between levels of the 3<i>d</i><sup>3</sup>, 3<i>d</i><sup>3</sup>4<i>s</i>, and 3<i>d</i><sup>3</sup>4<i>d</i> configurations and levels of the 3<i>d</i><sup>3</sup>4<i>p</i> configuration.
STANLEY J. YAROSEWICK and FRANK L. MOORE, JR., "Analysis of the Spectrum of Triply Ionized Manganese (Mn IV)," J. Opt. Soc. Am. 57, 1381-1383 (1967)