Constant ionic state spectroscopy of N₂O. Dispersed fluorescence as a probe of molecular autoionization

We report electronic autoionization studies of N₂O using vibrationally resolved constant ionic state (CIS) spectroscopy. Vacuum ultraviolet synchrotron radiation is the excitation source, and we determine the relative partial photoionization cross-section curves for alternative vibrational levels (ν′) of the ion by detecting dispersed fluorescence [N₂O⁺(A ²Σ⁺,v′→X ²Π,v″)] from the ion. Excitation spectra sampling different vibrational levels reveal significant changes in the 3π resonance profile, including shifts of the resonance minima, and previously unobserved features. Analysis of the v′=(0,1,0) CIS spectra demonstrate that this level of the ion is produced predominantly by photoionization of the target molecules in the (0,1,0) level, i.e., via hot band excitation. These results are discussed in detail, as well as possible extensions and further studies.