6533b82afe1ef96bd128ba4b
RESEARCH PRODUCT
A theoretical study of the 1B2u and 1B1u vibronic bands in benzene
Anders BernhardssonPer-a. ˚Ke MalmqvistLuis Serrano-andrésNiclas ForsbergBjörn O. Roossubject
:QUÍMICA::Química física [UNESCO]General Physics and AstronomyVibronic statesMolecular force constantsPerturbation theoryForce field (chemistry)Ground stateschemistry.chemical_compoundDipolechemistryOrganic compounds ; Vibronic states ; Perturbation theory ; SCF calculations ; Ground states ; Molecular force constantsOrganic compoundsUNESCO::QUÍMICA::Química físicaSCF calculationsMoleculeLinear approximationComplete active spacePhysical and Theoretical ChemistryAtomic physicsBenzeneGround stateExcitationdescription
The two lowest bands, 1B2u and 1B1u, of the electronic spectrum of the benzene molecule have been studied theoretically using a new method to compute vibronic excitation energies and intensities. The complete active space (CAS) self-contained field (SCF) method (with six active π-orbitals) was used to compute harmonic force field for the ground state and the 1B2u and 1B1u electronic states. A linear approximation has been used for the transition dipole as a function of the nuclear displacement coordinates. Derivatives of the transition dipole were computed using a variant of the CASSCF state interaction method. Multiconfigurational second-order perturbation theory (CASPT2) was used to obtain absolute excitation energies (12 active π-orbitals). The results show that the approach works well. Vibrational progressions are well described in both bands and intensities, and energies are in agreement with experiment, in particular when CASPT2 derived geometries are used. One interesting result is that computed vertical energies fall about 0.1 eV on the high energy side of the band maximum. Luis.Serrano@uv.es
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2000-02-08 |