Computer simulation of the structure, torsional potentials, excited state dynamics, and spectra of conjugated pi-electron systems

Valentin D. Vachev; John H. Frederick

doi:10.1117/12.220862

18 September 1995 Computer simulation of the structure, torsional potentials, excited state dynamics, and spectra of conjugated π-electron systems

Valentin D. Vachev, John H. Frederick

Author Affiliations +

Proceedings Volume 2548, Laser Techniques for State-Selected and State-to-State Chemistry III; (1995) https://doi.org/10.1117/12.220862
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

We present a theoretical-computational method for studying the excited structure and dynamics of conjugated (pi) -electron systems using spectra calculations, a normal mode analysis and a theoretical derivation of the correct Hamiltonian for constrained systems. We illustrate the method for the example of benzophenone. It is possible to reproduce very well the S₁ implied by S₀ absorption spectrum using a model with only four active modes, which we identify as (nu) ₆₄, (nu) ₆₂, (nu) ₂₇, and (nu) ₂₅. We present compelling evidence for the activity of a symmetric bending mode ((nu) ₆₂) with frequency of approximately 140 cm^-1 in the excited state. This result contrasts previous work based on models with activity in the asymmetric twist with frequency of approximately 70 or 100 cm^-1. We analyze the effects of deuteration and fluorine substituents, and show how the results could be used for an experimental test of the identity of the optically active modes.

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Valentin D. Vachev and John H. Frederick "Computer simulation of the structure, torsional potentials, excited state dynamics, and spectra of conjugated π-electron systems", Proc. SPIE 2548, Laser Techniques for State-Selected and State-to-State Chemistry III, (18 September 1995); https://doi.org/10.1117/12.220862

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