Gamma-gamma directional correlations in 201Hg

The directional correlations of the 135.3-32.2 keV and the 135.3-30.6 keV γ-γ cascades in 201Hg (following electron capture decay of 201Tl) were measured using a 5 cm x 5 cm NaI(Tl) detector and a 78.5 mm2 x 5 mm Si(Li) detector. The results obtained were W (theta) = 1 + (0.184 +- 0.030) P2(costheta) and W (theta) = 1 + (0.175 +- 0.040) P2(costheta), respectively. Starting with the known ground-state spins of 201Tl and 201Hg, the directional correlations give results consistent with the following spin assignments: 3/2-(0 keV), 3/2-(1.6 keV), 3/2-(32.2 keV), and 3/2-(167.4 keV). Assuming that the 135.3-keV γ transition is M1 + 0.1% E2 (which is consistent with internal-conversion measurements), the directional correlation results are consistent with multipolarities of M1 + < or = 0.3% E2 for the 32.2-keV γ ray and M1 + < or = 0.4% E2 for the 30.6-keV γ ray. The corresponding values of the mixing ratios are - 0.0634 < or = delta (30.6) < or = 0.0515 and - 0.0361 < or = delta (32.2) < or = 0.0506. These results are in mixed agreement with previous measurements