Second-Order Perturbation Theory in Atomic and Molecular Quantum Mechanics (Application to the Electric Dipole and Quadrupole Polarizabilities and Shielding Factors of the Beryllium Atom)

A new method, previously used in calculating atomic correlation energies, is shown to be applicable to a wide variety of atomic and molecular problems. Use is made of the fact that it is possible in many problems to calculate exactly the first-order perturbation correction to uncoupled Hartree—Fock wavefunctions and also second-order energy expressions. Particular application is made to the numerical calculation of dipole and quadrupole polarizabilities and shielding factors for the beryllium atom.