Theoretical and experimental evidence on charge transfer phenomenon of Th(IV) hydrolysis in aqueous medium

The present work reports one of the hydrolysis products of thorium is certainly undergoing charge transfer electronic transition. To study electronic transition of this species, absorbance was measured in the concentration range of Th(IV) ions from 1x10^-8 M to 1x10^-5 M in the absorption wavelength range of 190 nm to 400 nm. Absorbance was observed only in a narrow concentration range of 9.0x10^-7 M to 6x10^-6 M Th(lV) at 203 nm having molar extinction coefficient (ε) of 1x10⁶ L.mol^-1.cm^-1. Above and below this concentration range, absorption peak was not observed. The mass spectra study shows that the molecular ion peak is appearing at value 298.8 and it is close to molecular weight of Th(OH)₄. Further, theoretical absorption spectra of all possible species of Th(IV) hydrolysis were calculated using Gaussian 03 programme. Geometry optimizations were performed by time-dependent density functional theory (TD-DFT) at the Becker's three parameterized Lee-Yang-Par (B3LYP) and Stuttgart-Dresden effective core potentials basis set (SDD) was used. (author)