Quantum Mechanics and Dynamics of Open Polyatomic Systems

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We propose to study, both computationally and theoretically, various aspects of light-induced quantum dynamics of polyatomic (large) molecular systems that are coupled to an external environment. Such systems are ubiquitous in Chemistry, affecting all aspects of life. Indeed, the interaction of molecules with sunlight, in photosynthesis for example, is the primary source by which energy is transmitted to life on earth. In all cases to be studied we will proceed by developing formal theories, and building models containing the essential physical chemistry of the system examined. More complex modeling will be invoked when deemed enlightening. The work proposed is state-of-the-art in theoretical and computational chemistry, taking advantage of the most modern of parallel computer facilities. Such research often precedes and heralds developments in technology and industry, providing Canada with the edge in important advanced technological applications. The proposed program is also expected to provide the research environment and research challenges that are vital to the training of modern, highly qualified personnel. In addition to basic issues in light-matter interactions we will consider two major directions: (a) Coherent Control of Dynamic Processes is a foundational approach to controlling molecular processes via quantum interference effects. The methodology, based upon work that we have done over several decades, has been highly successful for small, isolated quantum systems. By contrast, control of larger molecules that are coupled to external environments (e.g., in solution or in a protein matrix) is a fertile field that we propose to explore in detail. The results are expected to significantly expand the range of control over processes in chemistry using quantum interference effects, an emergent technology for the coming century. (b) Open Quantum Systems are described by master equations, which are inherently subject to a wide collection of approximations (secular vs. nonsecular, Markovian vs. Non-Markovian, global vs. local couplings, low order perturbation theories, etc.). The choice of approximation has a profound influence on the resultant dynamics. We propose extensive studies designed to explore domains of validity of these approximate schemes for photosynthetic systems. Of importance here is the actual nature of the coupling between the system and environment, explored using a variety of methods. The results are expected to contribute significantly to the range of validity and applicability of master equation methods for light harvesting processes. In addition, we will examine issues related to the ability of photosynthetic systems to act as photon detectors, an issue of fundamental significance.