APPROACH FOR INCREASED INFORMATION FROM THE 2ND-DERIVATIVE SPECTRA IN UV-VIS ABSORPTION-SPECTROSCOPY

The resolution of overlapping bands in the UV-Vis absorption spectra leading to determination of their basic parameters (nu(max), epsilon(max), DELTAnu1/2) provides important information about the energies and probabilities of the electronic transitions. In the analysis of UV-Vis absorption spectra recorded linearly in wavelength by means of modern spectrophotometers with holographic gratings, the analytical shape describing individual bands is asymmetric. This factor leads to certain limitations in determining their number with the use of the second-derivative spectra and decreased effectiveness of the computing procedure. It was found that the loss of information in d2A/dlambda2 is due to its long-wavelength attenuation in comparison with d2A/dnu2. An analytical equation connecting d2A/dlambda2 with dA/dnu2 is proposed, which restores the information from the second derivative in the long-wavelength region.