Odd-parity autoionizing levels of uranium observed by two-color two-step photoionization optogalvanic spectroscopy

Miyabe, Masabumi   ; Satou, Yukihiko   ; Wakaida, Ikuo  ; Terabayashi, Ryohei*; Sonnenschein, V.*; Tomita, Hideki*; Zhao, Y.*; Sakamoto, Tetsuo*

Two-color two-step photoionization optogalvanic spectroscopy was performed using high-repetition-rate titanium sapphire lasers and a uranium hollow cathode lamp to find the two-step resonance ionization schemes of uranium. Many ionization transitions were observed by exciting uranium atoms in a ground state into five, even parity, excited levels with the first-step laser and by scanning the second-step laser wavelengths. By blocking the first-step laser, single-color, two-photon ionization transitions were also identified. From these results, we have found more than 50 odd-parity autoionizing levels of uranium in the energy, ranging from the ionization potential (49958.4 cm) to 51150 cm. The determined energy levels are within 1 cm of previously reported values.