Higher-order Sternheimer shieldings of the hydrogen atom

Abstract

Multiple perturbation theory is used to calculate the response of the electric field gradient at the nucleus of the hydrogen atom to external non-uniform fields. The parallel component of the field gradient at the nucleus in an axial field F with gradient F′ and second derivative F″ has the perturbation expansion:

For perturbations by a distant charge the terms of order R ^-4 and R ^-6 are reinforcing and combine to oppose the Sternheimer shielding which contributes at order R ^-3. Symmetry considerations for the general atomic case are discussed.