Quartic force fields (QFFs) have been shown to be an accurate computational tool in describing the vibrational frequencies and rotational constants of chemical systems that are inherently difficult to study with experimental methods.  Our investigation describes a flexible methodology that enables the accurate generation of spectral data for difficult systems building from the established use of QFFs for ground states but extending this to electronically excited states.  Previous ground state QFFs have made use of CCSD(T), the �gold-standard� of quantum chemistry, but the lack of a true wavefunction within CCSD(T) does not allow for a direct excited state extension.  As such, we will show the reliability of the approximate but iterative triples CC3 method for the computation of ground state QFFs and extend this to excited states.  EOM-CC3 has been shown to be a marked improvement over EOM-CCSD for the computation of electronically excited states of open-shell molecules.  The isoformyl radical (HOC) serves as our example system to demonstrate the capabilities of QFFs in elucidating rovibronic spectral data.

Quartic force fields for electronically excited states: Applications to the isoformyl radical

247th National Meeting (2014)

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