| dcterms.abstract | This thesis studies the dynamics in strong field ionization (SFI) of small molecules, with a focus on the removal of electrons from multiple molecular orbitals, especially the mechanisms underlying the population of excited ionic states. To do this, we ionize molecular systems with ultrafast intense laser pulses ( ~10 fs, > 10 TW/cm2) and measure photoelectrons and photoions in coincidence with velocity map imaging (VMI) detection. The ionization is multiphoton by design, and due to its highly non-linear nature, intense laser pulses provide adequate temporal resolutions for probing molecular dynamics and certain electronic dynamics. VMI measures the momentum distribution of charged particles, and together with coincidence detection, the full kinematics of an ionization event can be reconstructed from the measurement. This allows for detailed studies of ultrafast spectroscopy, and allows us to discriminate two different pathways in producing excited ionic states—either direct removal of an inner orbital electron or post-ionization excitation. For the latter, we carry out SFI experiments as well as theoretical simulations on a series of molecules, to study its dependence on electronic structure and the effect of non-adiabatic transition in populating excited ionic states, in particular, the importance of resonant transitions facilitated by nuclear dynamics. Additional work is focused on the strong field molecular double ionization (DI), where we conjecture a connection between enhanced DI yields and the electronic structure in conjugated molecular systems | |
