Nuclear matrix elements from L/K electron capture ratios in 59Ni decay

Using a recent theoretical method, the ratio of nuclear matrix elements R = (vF0220−√32AF0221/vF0211) was determined to be either 20.50+0.35−0.55 or 25.22+0.28−0.17 in the second-forbidden nonunique decay of 8 × 104 y 59Ni. These values of R were obtained from a value of L3/K = 0.008 ± 0.002 found by subtracting the theoretical ratio (L1 + L2)K = 0.113 (based on QPEC = 1070 ± 8 keV) from the total ratio L/K = 0.121 ± 0.002, which was measured with a reactor-produced, doubly-mass-separated 59Ni source introduced as gaseous nickel-ocene, (C5H5)2, into a wall-less, anticoincidence, multiwire proportional counter. The 854–1008 eV L and the 8.33 keV K peaks were measured simultaneously.