Gadolinium autoionization state

Recently, Bekov, Letokhov, Matveev and Mishin ) reported the observation of an autoionization state in gadolinium with the relatively long lifetime of 5 x 10 - s. The autoionization spectrum they observed by three-step laser spectroscopy is shown in Fig. 15. For isolated atoms, the width of the autoionization resonance is determined by its lifetime, so the 0.07 cm l half-width yields the estimated 0.5 ns lifetime. 

Laser spectroscopy methods substantially widen the scope of research into very narrow autoionization states. This can be illustrated by the long-lived autoionization state of the Gd atom (Bekov et al. 1978). Its lifetime is about 0.5ns, and Fa.i. 0.05 cm. A simplified energy-level diagram of gadolinium is shown in Fig. 9.4(a). The dye laser with Ai = 5618A used in the first excitation step raises gadolinium atoms from... 

Bekov, G. I., Letokhov, V. S., Matveyev, O. I., and Mishin, V. I. (1978). Detection of a long-lived autoionization state in the spectrum of gadolinium. Journal of Experimental and Theoretical Physics Letters, 28, 283-285. 

The use of autoionizing Rydberg levels converging to excited states of the ion to determine ionization potentials has been discussed above. If autoionization resonances as narrow as those found in gadolinium exist in the actinides, it should be possible to determine the isotope shifts and hfs of such features. (isotope shifts for actinides range up to 0.4 cm l per mass unit and odd atomic number actinides exhibit hfs with total widths of 4 to 6 cm l and hfs component spacing of 0.2 cm l or more for some transitions). 

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