Levels and transitions in 131Xe studied by the decay of oriented 131I

Sources of ¹³¹I were prepared by implantation in iron foils. Nuclear orientation of these sources was obtained by cooling them to temperatures of 30 to 50 mK using a dilution refrigerator and saturating the iron by an external magnetic field. Anisotropies of angular distributions of eleven γ-transitions in ¹³¹Xe have been measured, yielding the following results: the levels at 405 and 637 keV are $\text{3}\text{2}$⁽⁺⁾ and $\text{7}\text{2}$⁽⁺⁾ states and the assignment $\text{5}\text{2}$⁽⁺⁾ for the level a keV is confirmed. Deduced values of E2/M1 multipole mixing ratios are (energies in keV): ?0.5 ≦ δ(318) ≦ + 0.2; δ(364) = ?4.53±0.12; + 0.2 ≦ δ(405) ≦ +2.0; δ(723) = +0.207 ± 0.005. The allowed β-decay branch to the level at 637 keV is for at least 90% of the Gamow- Teller type.