FREQUENCY-DEPENDENT DIPOLE SHIELDING FACTORS

A frequency-dependent dipole shielding factor β infinity(ω) is defined as the coefficient of proportionality between the electric-dipole induced field and a uniform external electric field, at the nucleus, when the external field varies sinusoidally with time and with circular frequency ω. From oscillator sum rules it is shown that βinfinity(ω) = N/Z0 + ω 2α(ω)/Z0 where N is the number of electrons, Z0 is the nuclear charge and α(ω) is the dynamic dipole polarizability. Numerical calculations of βinfinity(ω) are reported for He, Be, Ne and several ions using coupled Hartree-Fock theory. It is found that calculations of βinfinity(ω) provide a severe test of the accuracy of zero- and first-order frequency-dependent wave functions.