  We study a system of two Coulombically interacting electrons in an external
harmonic potential in the presence of an on-centre Coulomb impurity. Detailed
results for the dependencies of the reduced von Neumann entropy on the control
parameters of the system are provided for both the ground state and the triplet
S states with the lowest energy. Among other features, it is found that in the
weak confinement regime the entanglement is strongly affected by the presence
of an acceptor impurity.
