High-resolution vacuum ultraviolet photodynamic of the nitrogen dioxide dimer (NO2)2 and the stability of its cation†
We report a comprehensive vacuum ultraviolet (VUV) photoionization study of the nitrogen dioxide dimer (NO2)2 by using a state-of-the-art method of double imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy at synchrotron SOLEIL. We find that the dimer cation N2O4+ from direct ionization of (NO2)2 is not stable and fully dissociates into the NO2+ and NO2 fragments. After identifying and separating the two different sources of NO2+ cations observed in experiments, direct photoionization of the monomer NO2 and dissociative photoionization of the co-existing dimer (NO2)2, the pure mass-selected threshold photoelectron spectrum (TPES) of the dimer (NO2)2 has been recorded without the need of subtraction. An upper limit of the adiabatic ionization energy of the dimer (AIE ≤ 9.59 ± 0.05 eV) and the appearance energy of the NO2+ fragment (AE = 10.15 ± 0.05 eV) are also given. In addition, the state-selected dynamics of the five low-lying electronic states of the cation N2O4+ have been analyzed from the corresponding kinetic energy release distributions.
- This article is part of the themed collection: 2020 PCCP HOT Articles