Orbital electron capture ratios in the decay of 205Pb

Abstract

The M/L and N/M electron capture ratios in the decay of 205Pb have been determined by introducing the radioactive compound tetramethyllead, 205Pb(CH 3) 4, into a wall-less multiwire proportional counter as part of the counting gas mixture. The results are: P M P L = 0.525 ± 0.008 and P N P M = 0.271 ± 0.010 . These results are compared to the theory of Behrens and Bühring using the relativistic wave functions of Mann and Waber. The comparison, along with an estimate of the overlap-exchange correction factor, gives a value of Q EC = 41.4 ± 1.1 keV. The half-life of 205Pb is deduced from the results to be (1.51 ± 0.04) × 10 7 y.