TDPAC-studies of 111In-complexes with organic ligands

The time differential perturbed angular γγ-correlation (TDPAC) method allows investigating some properties of condensed matter and is being applied world-wide in a broad field of solid state physics, material sciences, biology, medical chemistry, etc. It can be used, in particular, for studies of metal-ligand complexes molecular characteristics in dilute solutions and of radioactive decay after-effects. In TDPAC studies, 111In-is one of the most frequently used isotopes. One can say that it plays the same role as 57Fe in Moessbauer spectroscopy. 111In decays into 111Cd by electron capture (EC), and the 172-245 keV γ-ray cascade proceeding via the intermediate level with I=5/2, Q=0.8 b and T1/2=84 ns is being used in the TDPAC experiments. Auger-electrons emission, ionisation of daughter Cd atom and Coulomb repulsion as well as rearrangement of the chemical bonds around the new chemical element (formed as a result of EC) are regarded as EC after-effects. These processes can lead to high transient hyperfine electric fields at the daughter nucleus and to fragmentation of the In(Cd)-complexes with organic ligands. In(Cd)-complexes with diethylenetriaminepentaacetic (DTPA) acid, ethylenediaminetetraacetic (EDTA) acid, and nitrilotriacetic (NTA) acid were studied in the present work. Samples were prepared by dilution of 1 mg of ligand in 0.1 N HCI, adding the initial carrier-free 111InCl3 solution (the total radioactivity of samples did not exceed 10 μCi). The solutions were neutralised by 0.1 N NaOH. TDPAC measurements were performed at room temperature. The TDPAC anisotropy R(t) was fitted by the equation using the least square method