6533b871fe1ef96bd12d193e
RESEARCH PRODUCT
Vibrational analysis of the electronic spectrum of ethylene based onab initio SCF-CI calculations
Sigrid D. PeyerimhoffSigrid D. PeyerimhoffRobert J. Buenkersubject
ChemistryTransition dipole momentAb initioMolecular electronic transitionsymbols.namesakeAb initio quantum chemistry methodsRydberg formulasymbolsChiropracticsPhysics::Chemical PhysicsPhysical and Theoretical ChemistryAtomic physicsAbsorption (electromagnetic radiation)Wave functionExcitationdescription
Ab initio calculations for CH2 twisting and CC stretching vibrational wavefunctions and energy levels are reported for various electronic states of ethylene C2H4. Electronic transition moments between these states are also obtained to allow a calculation of the oscillator strengths for vibrational transitions involved in various electronic band systems; from this study it is concluded that thevertical electronic energy differenceΔE e may differ significantly from the energy of the absorption maximumΔE max with which it is often equated. In particular it is found in the case of theπ→π * singlet-singlet excitation of ethylene that theΔE e value overestimates the most probable vibrational transition energy (7.89 eV) by some 0.4 eV, thereby offering an explanation for the fact that previous attempts to predict the location of theV-N Franck-Condon absorption maximum have consistently obtained substantially higher results than the 7.66 eV value actually observed. Similar calculations for various Rydberg species and for theN-T transition are also found to obtain a quite consistent representation of the electronic spectrum of this system.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1972-01-01 | Theoretica Chimica Acta |