Photoionization of CH3N3 Produces 3B2 N3–: A Theoretical and Experimental Study of the Ion-Pair Channel

Abstract

We observe two ion formation thresholds when monochromatized synchrotron radiation is tuned through the onset of the methyl azide ion-pair channel (CH3N3 + hν → CH3+ + N3–). We assign these to production of the two lowest electronic states of the azide anion: the singlet linear (1Σg+) and the triplet bent (3B2) forms of N3–. This finding is supported by extensive quantum chemical calculations on the N3– 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 D0(CH3–N3) is suggested.