Observation of isotope shift in autoionization levels of uranium atom

The 235U was ionized with high selectivity using the two-wavelength two-step resonance photoionization. The autoionization level of this scheme has a large isotope shift of 0.51 cm-1 and a narrow spectral line width of 0.08 cm-1. It was found that high selectivity of 235U ionization is due to not only an isotope shift of the intermediate level but also large isotope shift and narrow spectral line of the autoionization level. The life time of the intermediate level of this ionization scheme, 23197 cm-1, was measured by the delayed coincidence method and was obtained to be 215 ns. (author)