  Background: The accurate determination of atomic final states following
nuclear $\beta$ decay plays an important role in many experiments. In
particular, the charge state distributions of ions following nuclear $\beta$
decay are important for determinations of the $\beta-\nu$ angular correlation
with improved precision. Purpose: Our measurement aims at providing benchmarks
to test theoretical calculations. Method: The kinematics of Li$^{n+}$ ions
produced following the $\beta$ decay of $^6{\rm He}$ within an electric field
were measured using $^6{\rm He}$ atoms in the metastable $(1s2s,~{^3S_1})$ and
in the $(1s2p,~{^3P_2})$ states confined by a magneto-optical trap. The
electron shake-off probabilities were deduced including their dependence on ion
energy. Results: We find significant discrepancies on the fractions of Li ions
in the different charge states with respect to a recent calculation and discuss
a plausible explanation. We also point out that there is no explanation for a
large discrepancy between the same calculation and a previous measurement of
the Li-ion energy dependence of the charge distribution from decays of the
electronic ground state.
