  In this review we study the level of accuracy of the electronic wave
functions which is necessary to describe properly the atomic effects during
nuclear beta-decay. In the case of the beta- decay in the Li atom into Be+ ion
we compare the numerical values of the transition probabilities from the S-,
P-, D-low-lying states of the initial atom and final ion calculated using both
Hylleraas-Configuration Interaction (Hy-CI) and Configuration Interaction (CI)
with Slater orbitals wave functions. In addition using the CI method the
transition probabilities from F, G, H and I low-lying states have been
calculated. The average of the absolute deviation of the transition
probabilities distribution for low-lying S-states is <0.15%, for P-states
<0.5%, and larger for D- and higher energy states. The numerical results
demonstrate that for low-lying states the atomic effect parameters in
beta-decay can be calculated with sufficient accuracy using CI wave functions
constructed with Slater orbitals. This result opens a new avenue for the
accurate calculation of atomic effects during the beta-decay in heavier atoms
and molecules.
