High resolutionlaser-induced fluorescence spectroscopy has been applied to investigate the isotope shift and hyperfine constant of high-lying odd-parity levels of the gadolinium atom.The isotope shifts were obtained for seven-transitions and hyperfine constants were determined for three levels of the configuration 4F75d6s7s 9D0.

The selective photoionization scheme for separating 157Gd from natural gadolinium and the laser irradiation conditions in order to enrich 157Gd to 60-80% are discussed in the case of twoand three-step photoionization. The dependence of excitation pathways on J-values is also discussed. From the view point of ionization rate it is preferable to select the four-colour threestep photoionization scheme by using both the ground and (he lowest metastable levels. Optimum laser irradiation conditions for gadolinium isotope separation are presented.

A computer simulation code to treat atomic excitation and laser beam propagation simultaneously in an atomic laser isotope separation system has been developed. The three-level Bloch-Maxwell equations are solved numerically to analyze the change of pulse shapes, the modification of laser frequencies and the time-varying atomic populations. The near-resonant effects on the propagation of frequency chirped and non-chirped laser pulses have been analyzed. It was found that there are serious differences in pulse shapes, frequency modifications and propagation velocities between laser pulses with and without chirping.