Theoretical Studies of Spectroscopy and Dynamics of Molecular Systems

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Hua Guo of the University of New Mexico is supported by the Theoretical and Computational Chemistry Program to develop accurate and efficient methods to study highly excited spectroscopy and reaction dynamics of small molecular systems. Methods to be employed are based on recursive generation of the Krylov subspace in which the eigenproblem is partially solved. Since the major computational task involves matrix-vector multiplications, such methods have favorable scaling laws. With prudently chosen discretization schemes, recursive methods such as the Lanczos algorithm or the Chebyshev propagation allow efficient computation of highly excited ro-vibrational levels as well as reaction probabilities, cross sections, and rates of systems affected by long-lived resonances. The prototypical system methylene, of interest due to the presence of Renner-Teller coupling and several conical intersections, will be studied using high level at initio calculations including a new strategy. The other system to be investigated is acetylene and its higher energy vinylidene isomer. To characterize this fundamental isomerization in full dimension, a new scheme will be applied to converge all vibrational levels below the isomerization barrier.This research is at the cutting edge of theoretical chemical physics, with outcomes expected to provide valuable insights into experimental observations of important molecular systems and associated chemical processes. As well, computational methodologies will be advanced in general, with computer codes resulting from the research to be made freely accessible to interested researchers. Since this project deals with large eigen or linear equation solvers, outcomes may benefit other fields in science and engineering where similar problems emerge. Examples include but are not limited to high-resolution imaging, nanomaterials, photonic crystals, and biophysics.