RESONANT 3-PHOTON PHOTOIONIZATION OF SM ATOMS

We investigated the resonant photoionization scheme of Sm by a three-c olor, three-step, three-photon ionization experiment. The first resona nt step was fixed at a well-known transition from the ground state, [4 f(6)6s(2)]F-7(1), to the state [4f(6)6s6p]F-7(2)0 of which energy is 1 7190.2 cm(-1). The second laser was scanned in the range of 552 - 601 nm to observe the even-parity states which are accessible from the [4f (6)6s6p]F-7(2)0 state. Thirty-six states were observed and their isoto pe shifts between even isotopes were measured originally by a three-st ep resonant ionization. From consideration of the measured data, we de termined the second resonant transition with the large isotope shifts. Additionally, an autoionization state with a large photoionization cr oss-section was found.