The Hyperfine Structure of Cs II

The first spark spectrum of caesium was photographed in the visible region with equipment including an electrodeless discharge, a Fabry-Perot interferometer, and a glass Littrow-type spectrograph. The hyperfine structure of thirteen lines was measured and twelve of the patterns were analyzed and identified as being caused by transitions between the 5p⁵(²P1/2)6p terms and the 5p⁵(²P1/2)5d, $6s$, $6d$, $7s$, and 5p⁵(²P11/2)7d,8s terms of the energy level scheme established by Sawyer, Olthoff, and others. This analysis verified the J values of seven levels given by Olthoff and Sawyer, determined the interval factors for nine energy levels, established one new energy level, and fixed the J value for one of the levels suggested by Ricard. A tentative identification of the two terms with the largest interval factor as 5p⁵(²P1/2)6s¹P₁ and 5p⁵(²P1/2)7s¹P₁ leads to 202,263 cm^-1 as an approximate value of 5p⁶¹S₀.