The hollow cathode spectrum of cadmium has been observed over the wave-length range from 600A to 6500A. In Cd I the 3D series has been resolved and extended. In Cd II the work of von Salis and Takahashi has been corrected and considerably extended. The 2P and 2F series are very perturbed by the overlapping 4d95s5p configuration which is nearly complete. No series terms have been found in the 4d95sns series. Cd III is excited very strongly in the discharge and the analysis is now much extended. The odd terms are from 4d95p and they combine with 4d10, 4d95s, 4d96s, 4d95d, and 4d85s2. An ionization potential of 37.6 volts can be calculated from the 4d9ns series.
A. G. SHENSTONE and J. T. PITTENGER, "Cadmium Spectra," J. Opt. Soc. Am. 39, 219-225 (1949)