Shape and Feshbach resonances in inner-shell photodetachment of negative ions
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abstract
Inner-shell photodetachment of negative ions has been investigated using the photon-ion merged beam technique for atomic and small cluster systems. The case of atomic systems is illustrated by reporting on the first measurements of the absolute cross-sections for the formation of Pt+, Pt 2+, and Pt3+ following 4f and 5p inner-shell photoexcitation and detachment of Pt- 4f145d 96s22D. The Pt3+ production channel is dominated by 4f detachment and allows for the first observation of a d-wave Wigner threshold law following single-photon absorption. Our measurements show that promoting a 5p electron into the 5d orbital produces a shape resonance, while promoting a 4f electron produces Feshbach resonances, demonstrating the importance of core-valence interactions. The photodetachment of small cluster systems is illustrated with the measurement and the calculation of K-shell photodetachment of size-selected B2- and B 3- clusters. The experimental absolute photodetachment cross-sections exhibit bound resonances below threshold and two shape resonances above the K-shell threshold. Similar results were obtained for all of the cationic products observed, B+ and B2+ from B2-, as well as B+, B2+ and B3+ from B3-. The overall agreement between measured and calculated photodetachment cross-sections is very good. 2010 Elsevier B.V. All rights reserved.
