A simple polynomial variational-perturbative approach to the evaluation of dynamic multipole polarizabilities for a ground-state hydrogen atom

Small well-shaped basis sets have been used to perform highly accurate variational-perturbative evaluations of dynamic (frequency-dependent) multipole polarizabilities for a hydrogen atom in its ground state. Their structure has been suggested by the ab initio polynomial power expansion we have recently developed to get correspondingly exact results within a finite range covering the region of low frequencies. The frequency-dependent coefficients of the optimized linear combinations of the excited pseudostate orbitals were obtained by diagonalizing the representative matrix of the excitation operator from the ground state. High levels of accuracy have been observed over a set of frequencies now covering the complete real and imaginary ranges. (C) 2001 Elsevier Science B.V. All rights reserved.