Orbital-Electron-Capture Ratios in the Decay ofFe55

Abstract

The M/I and I /E. orbital-electron-capture ratios in the decay of~5 Fe have been determined by introducing the radioactive compound ferrocene-~5Fe into a multiwire, wall-less anticoincidence proportional counter as part of the counting gas mixture. The results are P~/Pl =0.157+ 0.003 and PL /Pz =0.117+0.001 at Z =26. These values are compared with various theoretical predictions and, together with previous experimental results on M/L capture ratios at low Z, they demonstrate that of all the combinations of theoretical approaches, the Watson-Freeman wave functions with the exchange corrections of Vatai are the only ones which give good agreement with experiment at low Z. All other theoretical combinations lie considerably higher than experiment in the region below Z =36.

Variable Tl, Pb, and Cd concentrations and isotope compositions of enstatite and ordinary chondrites—Evidence for volatile element mobilization and decay of extinct 205Pb

“…] processes. The nuclide 205 Pb, which decays to 205 Tl with a half-life of 15.1 Ma (Pengra et al 1978), has thereby received attention for many years. This stems from the suggestion that it is unique among extinct radionuclides, as it may be produced solely by the s-process of nucleosynthesis (e.g., Blake et al 1973;Yokoi et al 1985;Wasserburg et al 1994Wasserburg et al , 2006.…”

Orbital electron capture by the nucleus

“…The degradation correction can amount to several percent but has not been taken into account in many investigations. This leads to appreciable differences in results (Heuer, 1966;Totzek and Hoffmann, 1967;Genz et al, 1971a;Pengra et al, 1972). Uncertainties in k and k have been greatly reduced since the new calculations of Scofield (1974) became available, which agree very well with experiment (Scofield, 1975).…”

“…These improvements were attained with more sophisticated low-noise electronics and through an understanding of the degradation spectrum (Genz et al, 1971a) and of after-pulses . Single-and few-electron peaks have been resolved on the basis of their spectral shape (Renier et al, 1968) or by fitting a Poisson distribution (Genz et al, 1971aPengra et al, 1972).…”

K-electron capture probabilities in the decays of Gd151 and Dy159

“…For the M capture no exchange and overlap correction is made and X u/L is assumed to be equal to 1. This assumption is based on recent experiments [16][17][18] which indicate that Bahcall's values for X mL are over estimated. Recent calculations by Vatai [15], in which interactions with electrons in outer shells (larger than M) and rearrangement are taken into account, bring down these estimates for X M/L slightly lower, while X L/K estimates are not altered.…”