Calculating Vibrational Excited State Absorptions with Excited State Constrained Minimized Energy Surfaces
Journal of Physical Chemistry A, 2023, Volume 127, pp. 5491-5501.
The modeling and interpretation of vibrational spectraare crucialfor studying reaction dynamics using vibrational spectroscopy. Mostprior theoretical developments focused on describing fundamental vibrationaltransitions while fewer developments focused on vibrational excitedstate absorptions. In this study, we present a new method that usesexcited state constrained minimized energy surfaces (CMESs) to describevibrational excited state absorptions. The excited state CMESs areobtained similarly to the previous ground state CMES development inour group but with additional wave function orthogonality constraints.Using a series of model systems, including the harmonic oscillator,Morse potential, double-well potential, quartic potential, and two-dimensionalanharmonic potential, we demonstrate that this new procedure providesgood estimations of the transition frequencies for vibrational excitedstate absorptions. These results are significantly better than thoseobtained from harmonic approximations using conventional potentialenergy surfaces, demonstrating the promise of excited state CMES-basedmethods for calculating vibrational excited state absorptions in realsystems.
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