Forced autoionisation in the Yb 6snd series

Abstract

We have observed the conversion of a level perturbing the Yb series into a forced autoionisation resonance by the application of a static field. The perturbing level is barely visible in the zero field excitation spectrum, leading us to expect the forced autoionisation resonance to be manifested as a dip in the spectrum as a Fano 0 feature. Instead, we observe a pronounced peak with a 3. As shown by a quantum defect theory analysis, the zero field spectrum is consisitent with 3. The apparent discrepancy arises from the combination of the rapid radiative decay of the perturbing level, the weakness of the configuration interaction and the discreteness of the zero field spectrum.