Symmetry-forbidden electronic state interference observed in angularly resolved NO+ (A 1Π) deexcitation spectra of the N*O(2σ(-1)2π(2)) resonance.

Quantum mechanical interference between different pathways in inner-shell resonance excitation-deexcitation spectra is a realization of a double-slit experiment on the atomic scale. If the intermediate inner-shell resonances are of different symmetries, this interference is symmetry forbidden in the solid-angle-averaged or magic-angle-recorded deexcitation spectra. It has, however, been suggested that interference may by observable in off-magic-angle-recorded spectra. Here, we prove this interference in angularly resolved deexcitation spectra of the 2σ(-1)2π(2)(2Δ,2Σ±) resonances of N*O by a quantitative comparison between ab initio calculations and experiment.

H2 superexcited states: experimental and theoretical characterization of their competing decay-channel fluorescence, dissociation, and ionization.

The absolute cross sections for the competing decay channels fluorescence, dissociation, and ionization of photoexcited long-lived superexcited H(2) molecular levels have been measured from the ionization threshold of H(2) up to the H(1s)+H(n=3) dissociation limit. The total and partial natural widths of these levels have been determined. Good agreement is found with first principles calculations carried out by multichannel quantum defect theory. The calculations reproduce the balance between the competing decay processes as well as its substantial level-to-level evolution.