Quantum dynamical modelling of photochemistry in gas-phase and complex environments

Understanding the chemistry in our atmosphere requires, at the fundamental level, a mechanistic understanding of the various processes taking place. Many steps in the large reaction networks involve photochemical reactions and dissociation plays a particularly important role. From a theoretical standpoint, modelling such processes is challenging due to the highly non-equilibrium nature of the problem. In this presentation, it will be demonstrated how accurate quantum chemistry methods can be used to characterise excited states of key molecules (e.g. methanol), and how quantum dynamical simulations are then able to fully describe the dissociation pathways accessible in a given range of wavelengths. Quantitative branching ratios can be automatically obtained for each channel, along with their timescales, which offers valuable information for atmospheric modellers. Furthermore, a newly developed procedure is also discussed, which allows these same quantum dynamics simulations to be performed in an explicit, atomistic environment. Applying these techiques to atmospherically relevant systems is sure to yield valuable insights and to reduce error bars on many of the parameters used in large scale models.