Wave-function collapse with increasing ionization: 4d photoabsorption of Cs through Cs4+ - art. no. 022702

The 4d relative photoabsorption cross section of cesium has been observed t o change dramatically in appearance along the isonuclear sequence Cs throug h Cs4+. Tn each case, discrete structure is observed below threshold and fo r Cs through Cs2+, a giant dipole 4d --> epsilonf resonance is also present above threshold. Between Cs2+ and Cs3+, there is a striking change, with m uch of the oscillator strength available in the 4d --> f channel being abru ptly transferred to the discrete spectrum. Despite the complexity of the tr ansitions involved, the oscillator strength envelope for the discrete trans itions yields relatively few features and remains essentially static in ene rgy regardless of the parent terms. Hartree-Fock with configuration interac tion and time-dependent local-density-approximation calculations successful ly account for this behavior and permit identification of the discrete feat ures.