Interchannel interactions following shape resonant excitation of core electrons

Interchannel coupling of a core electron shape resonance with a valence-hole ionic continuum is studied with vibrational resolution. A core-hole shape resonance is created via N₂ (1s→continuum e^-) photoabsorption, and this complex decays to form the N₂⁺ (B²Σ_u⁺) state via continuum interchannel coupling. The vibrational branching ratios for the N₂⁺ (B²Σ_u⁺) state are then determined from N₂⁺ (B²Σ_u⁺→²Σ_g⁺) fluorescence. The molecular motion provides excellent sensitivity to the resonant excitation, as underscored by two observations. First, the vibrational branching ratios for resonant and nonresonant excitation are qualitatively different. Secondly, the rotational motion of the ion is affected by the resonant excitation. These measurements demonstrate that continuum interchannel coupling can be probed precisely via dispersed fluorescence.