ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Resonance Raman spectra of o-chloranil were obtained by exciting the energetically lowest π–π* transition. Raman signals of three totally symmetric stretching modes (C=C, C=O, and C–C) showed pronounced intensity alterations. The intensity changes of these modes were analyzed using a dispersion formula which is based on the Kramers–Heisenberg–Dirac equation. Three-dimensional Franck–Condon integrals were calculated with the algorithm of Kupka and Cribb. The mathematical fitting of the experimentally derived spectra yielded the displacements of the potential curves along the considered normal coordinates and data of the Duschinsky mode mixing. The geometrical shifts along directions of ground-state normal coordinates were transformed to bond-length changes with the use of the eigenvector matrix L of the ground-state vibrations. L was obtained by a complete force field analysis. The excited-state geometry of o-chloranil is characterized by the contraction of the di-keto system accompanied by a weakening of the acrolein unit. The largest changes appear in the butadiene subsystem, where a conversion of bond order occurs between the double bonds and the single bond.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.465325
