Photodissociation studies using velocity ion imaging method, and, High-level ab initio calculations of molecular energetic and spectroscopic properties and benchmarking with experiments

An ion imaging apparatus using the velocity mapping and time slicing techniques has been constructed based on extensive ion trajectory simulations. The velocity calibration of the apparatus has been performed with the multiphoton dissociation/ionization processes of oxygen molecule. In this calibration experiment, we found that the energy resolution (Δ E/E) achieved for O fragment is in on the order of 3.0%. The apparatus has been employed to study the photodissociations of acetone, deuterated acetone and acetyl bromide.;The couple cluster theory including single, double excitations and a perturbative triple excitation together with complete basis set extrapolation method have been used to calculate the IEs of a number of polyatomic molecules and the AEs of selected dissociative photoionization processes. Furthermore, the calculations has taken into account correction/correlation terms, such as anharmonic ZPVE corrections, core-valence correlations, scalar-relativistic corrections, atomic/molecular spin-orbit coupling effects, diagonal Born-Oppenheimer corrections and higher-order corrections. The derivations from experimental data using the proposed theoretical methodology are found to be within ±10 meV.;Finally, the synchrotron radiation based high-resolution vacuum ultraviolet (VUV) photoion-photoelectron (PFI-PE) method has been applied to a number of molecular systems: (i) The unimolecular dissociation reaction of energy-selected vinyl bromide cation to form vinyl radical and bromide atom near its threshold has been examined using the PFI-PE-photoion coincidence (PFI-PEPICO) method; (ii) The PFI-PE spectrum of boron trichloride in the region of 93590–95640 cm−1 has been measured using VUV laser as well as the dissociative photoionization process boron trichloride to form boron dichloride cation and chlorine atom using PFI-PEPICO method, have been reported; (iii) The dissociation of energy-selected deuterated ammonia cation to form deuterated amino radical cation and deuterium atom near its threshold has been investigated using the PFI-PEPICO method.