P. Vankampen et al., DRAMATIC CHANGES IN THE 3S AUTOIONIZATION PROCESS AT THE BEGINNING OFTHE AR-I SEQUENCE, Physical review letters, 78(16), 1997, pp. 3082-3085
The 3s --> np resonances were observed to change dramatically in appea
rance with increasing ionization along the ArI sequence, and within th
e 3s --> np channel of Ca2+. By applying the Dyson equation method to
positive ions for the first time, newly investigated double-electron p
rocesses were shown to play a crucial role in the interpretation of th
e resonance structure. The changes within the resonances result from t
heir position relative to the Cooper minima in the 3s and 3p photoabso
rption.