MULTIPHOTON EXCITATION OF BEUTLER-FANO RESONANCES VIA RYDBERG STATES

A new method of stepwise multiphoton excitation spectroscopy via an ex tended Rydberg orbital is described. It is shown to provide a useful p robe of high-angular-momentum states in the first-inner-shell spectrum of YbI. The ng series is extended, and clear spectroscopic identifica tions are obtained by using the fact that spectral line shapes and sym metries are, as expected, different from those observed by single-phot on excitation from the ground state. Detailed comparisons are made bet ween spectra recorded by single and by multiphoton excitation, and the differences are attributed to the different spatial extents of the re gion in which the excitation occurs.