A genetic algorithm approach to fitting polyatomic spectra via geometry shifts

Discrepancies between experimental and theoretical fluorescence/absorption spectra are minimized using a genetic algorithm to shift the calculated excited electronic surface position. The method depends on the extreme sensitivity of polyatomic Franck-Condon factors to the geometrical shift that molecules undergo upon electronic excitation and on the power of genetic algorithms to rapidly locate the required origin shift. Examples of harmonic alkylbenzene Franck-Condon spectra are used to illustrate the method.