Study of even-parity autoionization states of samarium atom by laser optogalvanic spectroscopy

Two-color two-step laser resonance ionization spectroscopy (RIS) was used to study autoionization states of neutral samarium atom (Sm I). Optogalvanic signals were detected from a Sm hollow cathode lamp which was used as an atomic source. Several metastable states of the ground state term were populated from the heated hollow cathode. The six intermediate states which had mutually different total angular momentum (J) values from I to 6 were excited using the first step dye laser from the ground state (J = 0) and three metastable states having J values of 3, 4 and 5. These six excitation channels were used to study systematically the autoionization states having the probable J values from 0 to 7. The 359 even-parity autoionization states were found and their J values were estimated. The 357 states among the 359 autoionization states were newly found in this experiment.