Spectral curve fitting of infrared spectra obtained from semi-crystalline polyester yarns

Infrared spectra of polymer yarns exhibit a large number of strongly overlapping peaks. One of the methods to study the physical yarn structure quantitatively is to resolve the spectra into separate bell-shaped peaks. Due to the overlapping peak patterns, curve fitting with steepest descent like procedures depend on accurate initial estimates of the peak parameters. We developed a non-local curve fitting procedure, based on a genetic algorithm, which proved to be less sensitive to initial estimates. The combination of a genetic algorithm with a nonlinear estimator, based on Marquardtʹs method, gave the best curve fitting results.