Weak decay of 130Ba and 132Ba: Geochemical measurements

The half-life of ¹³⁰Ba due to multichannel weak decay (2β⁺, 2EC, and ECβ⁺) has been determined for the first time by the measurement of the ¹³⁰Xe daughter accumulated in natural barite (BaSO₄) from the Belorechenskoe deposit in North Caucasus, Russia. The accumulation time was determined from U-Xe and K-Ar gas-retention ages measured in the same material, yielding a half-life for ¹³⁰Ba for all weak decay modes of 2.2+/-0.5×10²¹ yr (68% C.L.), about a factor of 2 lower than that predicted by the proton-neutron quasiparticle random phase approximation. From excess ¹³²Xe observed in this barite, the half-life for weak decay of ¹³²Ba can be estimated (T_1/2=1.3+/-0.9×10²¹ yr). However, this value is more tentative, since other sources of this isotope cannot be excluded, but the lower limit of 2.2×10²¹ yr remains firm.