| Abstract: | A semiempirical parametric method for calculating the vibrational structure of the electronic spectra of polyatomic molecules
is developed; the method is based on the adiabatic molecular model and uses a single parametric system for all excited states.
Within the model approach, simplified analytical expressions for potential surface variation during molecular excitation are
derived; the expressions include the principal terms according to the order of magnitude. The first and second derivatives
of Coulomb and resonance one-electron integrals with respect to natural coordinates in a basis set of hybrid atomic orbitals
are used as parameters. It is shown that the parameters possess distinct locality, are transferable in molecular series, and
may be easily ranked according to absolute values; describing a molecular model requires few most significant parameters.
Excitation-induced variations of potential surfaces and absorption spectra of some molecules (butadiene, hexatriene, octatetraene)
are calculated using only two parameters, which are the same for all molecules. The results of calculations are in good agreement
with the experimental data.
Supported by RFFR grant No. 95-03-08808.
V.I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Translated fromZhumal Struckturnoi Khimii, Vol. 37, No. 3, pp. 419–431, May–June, 1996. |
