Excitation energies and multiphoton dissociation-ionization of 1,4-pentadiene at 266 and 355 nm

摘要

The photodissociation (PD) and photoionization (PI) of 1,4-pentadiene (PDE), which result in the absorption of multiple photons, were studied both experimentally and theoretically. The PD and PI ions were the result of the interaction of a cooled molecular beam of PDE with laser radiation of wavelengths 266 and 355 nm, measured using a time of flight (TOF) mass spectrometer. There are several differences in the ionization patterns, with the wavelength as a common characteristic in the absence of the parent ion, and on the possible dissociation of the neutral species such as C_2H_3 and C_3H_5, which then dissociates and ionizes. To interpret the results, the potential energy surface (PES) of PDE was calculated. Using time-dependent density functional theory (TD-DFT), the excitation energies and potential energy surfaces along the two main dissociative coordinates, namely, C_2-C_3 and C _3-H, were also calculated. Possible mechanisms responsible for the formation of the observed ions are proposed: hydrogen loss, molecular hydrogen formation, simple C-C dissociation, total deprotonation and hydrogen transposition.