The method of reduced-added Green's function in quantum defect approximation ͓V. E. Chernov, D. L. Dorofeev, I. Yu. Kretinin, and B. A. Zon, Phys. Rev. A 71, 022505 ͑2005͔͒ is generalized for calculation of dynamic polarizabilities of nonpolar molecules. The method is applied to alkali-metal dimers Li 2 , Na 2 , and Rb 2 . The accuracy achieved in benchmark calculation ͑H 2 molecule͒ is comparable to that of ab initio calculations. 1 It was considered for a long time that QDT description is successful only for one electron over complete shells, e.g., for alkalimetal-like atoms and ions. After an error in earlier QDT has been corrected in Ref. ͓14͔, the modified QDT is capable to treat optical electron states in any complex atom. The wave function of such a state is determined by the QDs of the whole spectral series ͑not only by the QD of the given state͒.
The quantum defect Green function formalism is applied to calculate the dynamic scalar and tensor polarizabilities of some atoms in their excited states (21S, 23S, 21P and 23P for He, 21P and 23P for Be, 33P for Mg and 43P for Ca). Experimental and calculated oscillator strength values were used to provide an account for low-excited states (reduce–adding correction of the Green function) while the high-excited and continuum states are accounted semi-analytically. The calculated polarizability values are in good (within several per cent) agreement with the available experimental data and the ab initio numerical data.
The reduced-added Green's function technique in the quantum defect theory combines the advantages of analytical and ab initio methods in calculating frequency-dependent (dynamic) polarizabilities of atoms and molecules, providing an exact account for the high-excited and continuum electronic states. In the present paper this technique is modified to take into account the long-range dipole potential of a polar molecule core. The method developed is applied to calculation of the dynamic polarizability tensors of alkali-metal hydrides LiH and NaH as well as to some fluorides (CaF and BF) in the frequency range up to the first resonances. The results are in good agreement with ab initio calculations available for some frequencies.
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