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 70 960-72 500 cm-1 employing a two-step laser excitation scheme via the 5s5p 3P1 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 3D2 (11 ≤ n ≤ 52) and 5sns 3S1 (12 ≤ n ≤ 38) Rydberg series, whereas the 5snd 1D2 series have been detected from n = 11 to 26. A two-parameter fit to the transition energy of 5snd 3D2 series yields the binding energy of the 5s5p 3P1 level as 41 883.97 ± 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. 65 1404)