Abstract
Highly excited Rydberg and autoionized levels were investigated by using selective absorption spectroscopy and the space charge amplification method for detecting ions. The one-photon absorption spectrum from the ground state 6s2 1S0 has been recorded by scanning the emitted continuum from a mercury lamp with a 2 m Czerny-Turner monochromator. With the allowed resolution of 0.1 AA, 6snp 1P10 Rydberg states were observed up to n=45. Furthermore, two-photon absorption spectroscopy was performed using a 0.150 cm-1 tunable dye laser radiation over the range 4200-5600 AA. Even-parity states J=0 and J=2 belonging to the series 6sns and 6snd up to n=46 and n=77, respectively, and new autoionized levels belonging to 5dns and 5dnd configurations were observed.