The analysis of the Mn II spectrum has been extended by the classification of approximately 600 additional lines. Most of the newly identified terms belong to the triplet system, for which no levels have previously been located. Intersystem lines have been found which fix the relative positions of the septet, quintet, and triplet systems and all terms of these systems to be expected within 40,000 wave numbers of the ground state have been established. No singlet levels have as yet been located.
C. W. CURTIS, "The First Spark Spectrum of Manganese (Mn II)," J. Opt. Soc. Am. 42, 300-305 (1952)