Two photoionization thresholds of $N3$ produced by $ClN3$ photodissociation at 248 nm: Further evidence for cyclic $N3$

We present results of near-threshold photoionization of $N3$ photofragments produced by laser photodissociation of $ClN3$ at 248 nm. The time of flight of recoiling $N3$ is used to resolve two photochemical channels producing $N3$⁠, which exhibit different translational energy release. The two forms of $N3$ resolved in this way exhibit different photoionization thresholds, consistent with their assignment to linear $(XΠg2)$ and cyclic $N3$⁠. This result agrees with the existing theoretical calculations of excited and ionic states of $N3$ and strengthens previous experimental results which suggested that the $ClN3$ photolysis produces a cyclic form of $N3$⁠.