Photoabsorption and fluorescence excitation of malononitrile in the vacuum UV region

The cross-sections for the photoabsorption and fluorescence excitation of CH2(CN)2 were measured in the 105–200 nm region using synchrotron radiation. The absorption bands were interpreted in terms of the transitions to the valence and Rydberg states. The vibrational progressions observed in the Rydberg bands were assigned on the basis of ab initio MO calculations. CN(B2Σ+) and CN(A2Πi) photofragments were identified by a dispersed fluorescence spectrum. The fluorescence quantum yields for CN(B2Σ+) and CN(A2Πi) formation increase with decreasing excitation wavelengths. The CN(B2Σ+) quantum yield has a maximum of 0.85% at 107 nm.