  A semiempirical parametric method is proposed for modeling three-dimensional
(time-resolved) vibronic spectra of polyatomic molecules. The method is based
on the use of the fragment approach in the formation of molecular models for
excited electronic states and parametrization of these molecular fragments by
modeling conventional (one-dimensional) absorption and fluorescence spectra of
polyatomic molecules. All matrix elements that are required for calculation of
the spectra can be found by the methods developed. The time dependencies of the
populations of a great number (>10^3) of vibronic levels can be most
conveniently found by using the iterative numerical method of integration of
kinetic equations. Convenient numerical algorithms and specialized software for
PC are developed. Computer experiments showed the possibility of the real-time
modeling of three-dimensional spectra of polyatomic molecules containing
several tens of atoms.
