VUV Laser Spectroscopy of Ytterbium: 4f-excitation, Doubly-excited States and Their Mutual Interactions

Abstract New measurements of the auto-ionization spectrum of YbI were performed using a thermionic diode detector and a source of tunable VUV light based on a four-wave mixing scheme. In addition to a higher resolution than previous results our data provide much more reliable information on relative intensities and on the lineshapes of the auto-ionizing profiles. The latter reveal interesting interfaces due to interacting resonances. We present examples from a portion of the spectrum which includes single excitation manifolds built on an open 4f subshell and overlapping double-excitations of valence electrons in the wavelength range between 1391 A and 1415 A. Our data demonstrate a great improvement compared with earlier measurements.