Consistent calculation of the screening and exchange effects in allowed β − transitions

Xavier Mougeot (1) , Charlène Bisch (1)

1 LNHB (CEA, LIST) - Laboratoire National Henri Becquerel (CEA, LIST)

The atomic exchange effect has previously been demonstrated to have a great influence at low energy on the 241Pu β− transition. The screening effect has been given as a possible explanation for a remaining discrepancy. Improved calculations have been made to consistently evaluate these two atomic effects, compared here to the recent high-precision measurements of 241Pu and 63Ni β spectra. In this paper a screening correction has been defined to account for the spatial extension of the electron wave functions. Excellent overall agreement of about 1% from 500 eV to the end-point energy has been obtained for both β spectra, which demonstrates that a rather simple β decay model for allowed transitions, including atomic effects within an independent-particle model, is sufficient to describe well the current most precise measurements.

Mots clés: beta spectrum; metrology; radioactivity; ionizing radiation; beta-rays; electron wave; beta decay; particle model; Decay data evaluation

Domaines: Radiochimie; Physique Nucléaire Expérimentale [nucl-ex]

Xavier Mougeot, Charlène Bisch. Consistent calculation of the screening and exchange effects in allowed β − transitions. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2014, 90 (1), pp.012501(8). ⟨10.1103/PhysRevA.90.012501⟩. ⟨cea-01848119⟩