The structure and properties of molecules and their cations plays a fundamental role
in a range of dynamical studies such as; ultra-cold collisions, dissociative electron
attachment, radiative loss and association, photo-dissociation, electron scattering,
photo-ionization and ultrafast dynamics [1 – 7]. Recent experiments at light sources
such as the Advanced Light Source (ALS) in Berkeley, USA, SOLEIL in Saint Aubin,
France and PETRA III, in Hamburg, Germany, have investigated core excited states of
molecular system and their subsequent decay . The interpretation of experimental
results requires detailed information on the structure, properties and dynamics and is
a prime example where quantum chemistry plays a fundamental role.
Electron- density distributions and potential-energy surfaces are important for predicting the
physical properties and chemical reactivity of molecular systems. Angle-resolved
photo-electron spectroscopy enables the reconstruction of molecular-orbital
densities of species [8,9]. A brief review of the methods used to obtain the structure
and dynamics of molecular systems will be given and shown how this information can
be used to study a variety of molecular processes in systems such as; SH+,SiH+,NaCa+, SiO, CS, N2 and BaH.