Photofragment translation spectroscopy of ClN3 at 248 nm: Determination of the primary and secondary dissociation pathways

Photofragmentation translational spectroscopy was used to identify the primary and secondary reaction pathways in the KrF laser (248 nm) photodissociation of chlorine azide (ClN3) under collision-free conditions. Both the molecular channel producing NCl (X 3Σ,a 1Δ)+N2 and the radical channel producing Cl (2PJ)+N3 were analyzed in detail. Consistent with previously reported velocity map ion imaging experiments [N. Hansen and A. M. Wodtke, J. Phys. Chem. A 107, 10608 (2003)] a bimodal translational energy distribution is seen when Cl atoms are monitored at m/z=35(Cl+). Momentum-matched N3 counterfragments can be seen at m/z=42(N3+). The characteristics of the observed radical-channel data reflect the formation of linear azide radical and another high-energy form of N3 (HEF-N3) that exhibits many of the characteristics one would expect from cyclic N3. HEF-N3 can be directly detected by electron-impact ionization more than 100 μs after its formation. Products of the unimolecular dissociation of HEF-N3 are observed in the m/z=14(N+) and m/z=28(N2+) data. Anisotropy parameters were determined for the primary channels to be β=-0.3 for the NCl forming channel and β=1.7 and β=0.4 for the linear N3 and HEF-N3 forming channels, respectively. There is additional evidence for secondary photodissociation of N3 and of NCl