  We consider a simple atomic two-body bound state system that is overall
charge neutral and placed in a static electric and magnetic field, and
calculate the magneto-electric response function as a function of frequency.
This is done from first principles using a two-particle Hamiltonian for both an
harmonic oscillator and Coulomb binding potential. In the high frequency limit,
the response function falls off as 1/\omega^2 whilst at low frequencies it
tends to a constant value.
