Dissociative photoionization of ClN3 using high-resolution synchrotron radiation: The N–Cl bond energy in ClN3

High-resolution synchrotron-radiation-based photoionization mass spectrometry was applied to study the dissociative photoionization of ClN3 under collision-free molecular beam conditions at ionization energies between 10 and 17 eV. No parent ion (ClN3+) could be detected under our experimental conditions. This suggests that the ground and excited states of ClN3+ are weakly bound or repulsive, a conclusion supported by electronic structure calculations also reported here. We recorded photoionization yield spectra at m/z = 49, 42, 35 and 14 from which we extracted the appearance potentials for NCl+, N3+, Cl+, and N+. The appearance potential of NCl+ (10.17 ± 0.02 eV) observed here is close to the previously reported ionization potential of ClN3 obtained form photoelectron spectroscopy. Using the theoretically calculated binding energy of ClN3+ (0.2 eV), we derive an estimate of the adiabatic ionization potential of ClN3 = 9.97 ± 0.02 eV. The measured appearance potentials for N3+, Cl+, and N+ provide three independent determinations of the Cl–N bond energy in ClN3, which agree within their respective error limits. The observations of this work are consistent with a new value of the N–Cl bond energy in ClN3, D0(Cl–N3) = 1.86 ± 0.05 eV, 0.3 eV lower than previously reported values, which are however experimentally derived upper limits. The bond energy reported here is consistent with high level ab initio (CCSD(T)) electronic structure calculations extrapolated to the complete basis set limit, which yield a value: D0(Cl–N3) = 1.87 eV.