Ion dissociation dynamics of the chlorine azide cation (ClN3+) investigated by velocity map imaging

Abstract

The velocity map imaging technique was applied to study the unimolecular dissociation dynamics of the chlorine azide cation (ClN3+) fragmenting into N2 and NCl+ and the results have been compared to quantum chemical calculations. The ClN3+ ion was produced in a molecular beam by two-photon ionization of chlorine azide (ClN3) with laser light at λ≈202 nm. Rotationally resolved REMPI spectra and velocity map images of state selected N2(X 1Σg+,v,J) quantify the energy deposition into N2 and NCl+ products. Photoelectron velocity map images show near zero-energy electron production. Angular distributions of the photo-fragments suggest we are witnessing the influence of the ions first excited (A′) electronic state on its decomposition. The N2(X 1Σg+) dissociation products are mainly in the vibrational ground state, but rotationally excited with J up to ∼60. An unusual vibrational distribution in the NCl+ (X 2Π,v=1–12) product was observed, which is evidence of nonstatistical ion decomposition. This work also provides an accurate determination of the energetics for the reaction, ClN3+→N2(X 1Σg+)+NCl+(X 2Π)(ΔE<−0.2 eV), from which one may use prior photoionization threshold data to derive the energetics of the ClN3→N2(X 1Σg+)+NCl(a 1Δ)(ΔE<0.3 eV) dissociation.