Two-step laser spectroscopy of the highly excited even-parity levels of cadmium

We report experimental data on the highly excited even-parity states of cadmium in the energy range 70960-72500 cm(-1) employing a two-step laser excitation scheme via the 5s5p (3)p(1), inter-combination line. Two frequency doubled dye lasers simultaneously pumped by a common Nd:YAG laser were used to record the spectra using a thermionic diode ion detector. New observations include much-extended 5snd D-3(2) (11 <= n <= 52) and 5sns S-3(1), (12 <= n 38) Rydberg series, whereas the 5snd D-1(2) series have been detected from n I I to 26. A two-parameter fit to the transition energy of 5snd D-3(2) series yields the binding energy of the 5s5p (3)p(1), level as 41883.97 0.05 cm(-1) and, consequently, the first ionization potential of cadmium is determined as 72 540.06 0.13 cm(-1), in good agreement with that reported by Brown et al (1975 J. Opt. Soc. Am. 651404).