MULTIPHOTON EXCITATION OF BEUTLER-FANO RESONANCES VIA RYDBERG STATES

A new method of stepwise multiphoton excitation spectroscopy via an extended Rydberg orbital is described. It is shown to provide a useful probe of high-angular-momentum states in the first-inner-shell spectrum of YbI. The ng series is extended, and clear spectroscopic identifications are obtained by using the fact that spectral line shapes and symmetries are, as expected, different from those observed by single-photon excitation from the ground state. Detailed comparisons are made between spectra recorded by single and by multiphoton excitation, and the differences are attributed to the different spatial extents of the region in which the excitation occurs.