The Spectrum of Singly Ionized Phosphorus, P II

New observations in the P II spectrum have been made in the wavelength region 500-12 000 A. The spectrum was excited in two different ways, using a high-frequency lamp and a sliding spark in vacuum. The term system now includes 159 levels and about 900 identified lines, which means a doubling of the number of levels and identified transitions. The energy of the lowest limit, 3s2 3p 2P, is derived from ng-series, which are all new. A linear Ritz formula gives the value 160 010.6 cm-1 for the 2P3/2 component of the limit, and the ground term splitting 559.14 cm-1 in P III then gives 159 451.5 cm-1 for the 2P1/2 limit level.