VANISHING FLUCTUATIONS IN ATOMIC SPECTRA

Spectral fluctuations are discussed in the context of the K-matrix theory of interacting autoionizing resonances. New measurements of the doubly-excited spectrum of Ba I in the vicinity of the 6p1/2 threshold provide unambiguous evidence for the disappearance of fluctuations at a specific excitation energy well below the associated series limit. We discuss the origin of this effect, we show that it occurs close to the resonance energy of one broad intruder level, and we suggest a more general connection between the vanishing width effect and the disappearance of fluctuations in atomic spectra.