Photoionization of CH3N3 produces 3B2 N3-: A theoretical and experimental study of the ion-pair channel.

We observe two ion formation thresholds when monochromatized synchrotron radiation is tuned through the onset of the methyl azide ion-pair channel (CH3N3 + h nu -> CH3+ + N-3(-)). We assign these to production of the two lowest electronic states of the azide anion: the singlet linear ((1)Sigma(+)(g)) and the triplet bent (3B(2)) forms of N-3(-). This finding is supported by extensive quantum chemical calculations on the N-3(-) singlet and triplet potential energy surfaces. Quantum chemical calculations are also used to rule out alternative ionization channels that exhibit the same m/z ratios: NH+ + isomers of CH2N2- A value of 292.9 kJ/mol for the D-0(CH3-N-3) is suggested.