Gabriel Hanna

Biography

BSc, Laurentian University PhD, University of Toronto.

Research Interest

Mixed quantum-classical formulation of nonlinear spectroscopy (a) Simulating the quantum dynamics of processes occurring in classical condensed phase hosts Starting from the mixed quantum-classical Liouville (MQCL) equation of motion, it is possible to construct practical trajectory-based algorithms for simulating the dynamics of a quantum subsystem coupled to a classical environment. Over the past few years, several methods have been successfully applied in the treatment of simple model systems, but their implementation has been less straightforward in the case of more complex systems. It is our desire to develop and implement schemes based on the MQCL equation, which overcome the pitfalls of existing algorithms when dealing with complex, many-body systems. (b) Modeling of multidimensional nonlinear spectra Ultrafast nonlinear spectroscopy is capable of probing molecular dynamics on the femtosecond time scale. Often the resulting spectra are complex, thereby requiring a theoretical framework for their interpretation. Moreover, with comparisons between simulated and experimentally measured spectra becoming increasingly sophisticated, the development and implementation of accurate methods for modeling spectroscopic response is timely. The MQCL approach provides a convenient way for simulating laser-driven dynamics and will thus provide a suitable platform for the development of a general framework for calculating multidimensional nonlinear spectra. 2. Applications to the multidimensional infrared spectroscopy of chemical and biological systems in nanoconfined environments We are interested in simulating one- and two-dimensional infrared spectra to study the structure and dynamics of a wide variety of nanoconfined systems of experimental interest, some examples of which include: (a) Nanoconfined water In many chemical and biological systems, water molecules can be confined on nanometer length scales. Under these conditions, the molecules are in contact with different types of interfaces. Near an interface, the hydrogen bonding network of water changes considerably because it must adjust to the shape of that interface. As a result, the properties and dynamics of nanoconfined water differ substantially from those of bulk water and must therefore be studied in the presence of the interface. (b) Nanoconfined nonaqueous polar liquid clusters Proton transfer in nanoconfined nonaqueous polar liquid clusters represents a class of reactions that are ubiquitous in chemistry. This charge transfer reaction is strongly coupled to the polar solvent and will therefore be greatly affected by solvent confinement. For example, several experiments have shown that the proton transfer rate constant can decrease significantly upon confinement. As a result of this sensitivity, one may design materials with specific chemical purposes by simply varying properties of the cluster such as its size and shape. (c) Hydrogen transfer in enzymatic catalysis Hydrogen transfer reactions are ubiquitous in enzymatic catalysis. The interior of an enzyme can form a nanoconfined environment around its active site and this confinement may play an important role in its function. Studying the effects of factors such as hydrogen tunneling and enzymatic motions is crucial for a detailed understanding of the transfer mechanism.