Nuclear shielding factor is an important quantity to describe the response of
an atom under the perturbation of an external field. In questo lavoro, we develop
the sum-over-states numerical method and the Hylleraas variational perturbation
approximation to calculate the multipole nuclear shielding factors for general
one-electron systems and apply them to the model of the hydrogen atom confined
by a spherical cavity. The generalized pseudospectral method is employed to
solve the eigenstates of the unperturbed atom. The obtained dipole nuclear
shielding factors are in good agreement with previous calculations and the
higher-pole results are reported for the first time. The asymptotic behaviors
of the multipole nuclear shielding factors in both the large- E
small-confinement limits are analyzed with the assistance of variational
perturbation theory. The free-atom values can be exactly reproduced by the
second-order perturbation approximation and all multipole nuclear shielding
factors in the small-confinement limit tend to zero by a linear law. The
variational perturbation method manifests exponential convergence with
increasing the order of approximation. The numerical and approximate methods
developed in this work together pave the way for further investigation of the
multipole nuclear shielding factors for general atomic systems.

Questo articolo esplora i giri e le loro implicazioni.

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