The time differential perturbed angular correlation study of binding of hafnium to humic acid and its model compound

Time differential perturbed angular correlation (TDPAC) spectroscopy has been used to study the binding of hafnium to mandelic acid, which is a model compound of humic acid. The Fourier transform of TDPAC spectrum of Hf-mandelate complex showed two ω values, namely, ωQ1 = 77 (±0.4) Mrad/s and ωQ2 = 111 (±3.1) Mrad/s. The asymmetry parameters for the two sites were found to be 0.7 and 0.3, respectively. The electric field gradient (EFG) around the metal ion was theoretically calculated using the computer code GAMESS. The calculated EFG value was found to be in reasonable agreement with that deduced from experiment. Contrary to Hf-mandelate, the TDPAC spectrum of Hf-humate system did not show characteristic features of discrete binding sites.