Quantum-mechanical modeling of the dissociation of hydrogen bonds

ongoing

Hydrogen bonds are everywhere in nature, and they are important in many fields of science. Well-known examples come from biology (helix structure, protein folding, enzyme docking), chemistry (solvation, structure and properties of water), and atmospheric science (nucleation and growth of aerosols). Today, the spectroscopic features of hydrogen bonds are relatively well understood, but much less is known about the associated ultrafast dynamics. The theoretical models that are used to understand and design present ultrafast experiments are often based on classical or semi-classical approximations to describe the movement of the nuclei. With the recent advances in both theory and ultrafast imaging techniques, we believe that the time is ripe for a full quantum mechanical picture of hydrogen-bond dissociation. A quantum mechanical picture of hydrogen bond dissociation will contribute to the basic understanding of chemical, biological, and atmospheric processes. In this project, I will perform a comprehensive quantum mechanical study of the hydrogen-bond dissociation dynamics of a small hydrogen-bound complex, pyrrole-H2O. The calculations will be performed in a reduced-dimensional framework, for which the central hypothesis is that certain vibrations dictate the dissociation process while other vibrations serve as spectators. The dissociation process will be initiated through an infrared excitation that provides just enough energy to dissociate the complex, but not enough energy to initiate other unwanted processes. We will establish how the reaction mechanisms for hydrogen-bond dissociation manifest themselves in the ongoing ultrafast dynamics experiments performed in the Controlled Molecule Imaging (CMI) group. The calculations will be tailored to design and simulate realistic experiments, and to facilitate the analysis of the experimental results.