y-y directional correlation studies have been carried out on the (1063.62-569.67) keV 13/2+ + ='5/2~1/2 cascade in the decay of ' Bi using the time differential perturbed angular correlation method. The measurements show time dependent magnetic perturbation of the correlation. From the plot of A2(t) vs t (finite time resolution corrected), the value of the relaxation parameter g2 and the unperturbed A, (0) coefficient (solid angle corrected) obtained are (2.4 + 0.3) X 10 sec ' and 0.259 + 0.016, respectively. From the plot of Ao(t) vs t, the unperturbed value of T», and therefrom A. o for the 569.67 keV level are determined to be (130.7+1.3) ps and (5.30+0.06) X10' sec ', respectively. Using the Xo and X, values, the integral attenuation coefficient G,(oo) has been estimated to be 0.69 + 0.03. The differential data at various angles were integrated and the solid angle corrected A, (00) coefficient thus obtained is 0.204 + 0.005. The perturbation mechanism is discussed in the light of the spin-spin interactions between the 6s electrons of the neighboring paramagnetic Pb+++ ions. The results are found to be consistent with the theory of Abragam and Pound.HADIOACTIVITY