This dissertation focuses on the understanding the unimolecular photochemistry and dynamics
utilizing state-resolved slice imaging approach combined with the quantum-state selective
spectroscopy technique called resonance enhanced multi photon ionization (REMPI)
method. This powerful technique allows selecting the initial quantum states of the reactants
and determining the nal quantum states, energy, the orientation and alignments of
the products. In the investigations of photodissociation dynamics of acetone at 230 nm,
a bimodal distribution for the resulting CO photoproduct is identied. This observation
indicated the presence of unimolecular dissociation mechanism analogues to the roaming
dynamics reported in formaldehyde photodissociation. Moreover, another type of roaming
mechanism called \roaming-mediated isomerization is introduced in the study of nitrobenzene
photodissociation. In this study molecules undergo roaming type isomerization
before the simple bond ssion take place. In the study of photodissociation dynamics of
tertachloroethylene (TCE) at 235 nm and 202 nm using state resolved slice imaging approach
illustrate that the dissociation take place at the ground state despite the dierence in
the excitation energies. A similar spin-orbit branching ratio of Cl/Cl* at both wavelengths
are observed due to the above dynamical behavior of the molecule. In the study of HNO3
photodissociation near 204 nm report the translational energy and angular momentum distributions
of the resulting O(1D) product. The vibrational energy distribution of the HONO
co-product, as seen through the O(1D) translational energy distribution, shows signicant vibrational energy remaining in the molecule. Analysis of the angular distributions from
both the 1F3 \u3c-- \u3c-- 1D2 and 1P1 \u3c-- \u3c-- 1D2 O probe transitions oer additional insight into the
dynamics of the dissociation of nitric acid through the S3 (2 1A0 ) excited state, helping to
resolve some outstanding questions and pointing the way to future studies. This approach
allowed us to identify new mechanisms and channels created during the photodissociation
events, calculate the branching ratios and infer the complex reactive processes in combustion,
atmospheric and interstellar chemistry
