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The TDPAC technique was applied to verify a hypothesis about the influence of electron capture after-effects on the integrity of radiometal complexes with organic ligands in aqueous solutions. The neutral aqueous solutions of DTPA-complexes with two parent isotopes, 111 In(EC) 111 Cd and 111m Cd, were used for direct comparison of dynamic interaction parameters. Data for the parent 111 In–DTPA complexes revealed three fractions with essentially different relaxation constants, including an “unperturbed” fraction, which, according to the hypothesis, is due to small fragments of the initial complexes disintegrated as a result of Auger-process and the following Coulomb fragmentation. Only one fraction with a relaxation constant of 3(1)×10 6 s −1 was observed for the 111m Cd–DTPA solution confirming the proposal about the influence of electron capture after-effects. Measurements with the frozen solutions allowed determining the electric field gradient (EFG) at Cd-sites in complexes with DTPA, V zz =6.7(2)×10 21 V/m 2 with an asymmetry parameter η =0.75(5). |
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