Cyclohexene Valence Shell Excitation Probed by Synchrotron Radiation and Quantum Chemical Calculations

A comprehensive investigation is presented for cyclohexene, C6H10, via the vacuum ultraviolet (VUV) absorption spectrum in the photon energy range 4.0–10.8 eV (310–115 nm). Quantum chemical calculations (Density Functional Theory (DFT), Time Dependent Density Functional Theory (TD-DFT) and Equation of Motion Coupled-Cluster Single and Doubles (EOM-CCSD)) are combined with experiments in order to provide the most accurate and up-to-date information about the electronic state spectroscopy of cyclohexene. The spectrum reveals several new features not previously reported in the literature, with special attention to the different Rydberg series converging to (11b)−1 X~2B, (10b)−1 A~2B, (12a)−1 B~2A, (11a)−1 C~2A, and (9b)−1 D~2B ionic electronic states of cyclohexene. We also provide absolute cross-section values from high-resolution VUV photoabsorption measurements, with photolysis lifetimes in the Earth’s atmosphere from 0 to 50 km altitude being obtained, showing that solar photolysis is not an important sink mechanism at altitudes lower than 22 km, relative to ●OH radical reactions.