Solar energy presently provides as many promises for abundant, renewable energy as it does questions for the field of chemistry.  One of the potential routes to uncover the molecular-level details of solar energy chemistry is vibrational spectroscopy, which probes the response of molecules to infrared radiation.  Considerable progress has been made along these lines in recent years, but bridging these experiments with meaningful, chemical insights often requires high-quality computer software for interpretation.  This research program will discover and develop new approaches for computational simulations of this molecular motion.  Specifically, the research will decipher the connection between the behavior of electrons inside of molecules and the accordant molecular vibrations.  Working closely with committed experimental collaborators, this conceptual and computational framework will be used to explain the results of new spectroscopy experiments.  The resulting products of the research program will include openly available software and algorithms for the simulation of challenging vibrational spectra, as well as critical mechanistic insight into energy-focused catalytic processes that are opaque to other existing analytical techniques.