Quantum Chemistry methods are used to calculate the structure and the dynamics of small stable and unstable molecular species,
having a direct experimental interest in fields like chemical reactivity, spectroscopy, atmospheric chemistry and astrophysics. We
mainly focus on excited electronic and vibrational states, which play a decisive role in many reactive processes (dissociation,
predissociation, isomerization, intramolecular vibrational relaxation...). Adapted  methods of calculation are developed in order to
take the underlying interactions into account (electron correlation,  vibrational anharmonicity, vibronic coupling, intra-molecular
interactions). We also perform ab initio calculations on the building blocks of biomolecules, marking a special interest for the
ionisation phenomena relevant in the field of radiative damage to the genetic material.