THE EVALUATION OF MCRPA(MCTDHF) ELECTRONIC EXCITATION-ENERGIES, OSCILLATOR-STRENGTHS, AND POLARIZABILITIES - APPLICATION TO O-2
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We derive the multiconfigurational random phase approximation (MCRPA) by requiring the equivalence between the length and velocity forms of the oscillator strength. The MCRPA is also justified in terms of the equations of motion (EOM) formalism. The final equations and techniques developed are the same as the multiconfigurational time dependent HartreeFock (MCTDHF). We explicitly demonstrate the validity of the energyweighted sum rule for the MCRPAMCTDHF. A modification of our previously derived MCTDHF technique is introduced. This involves the incorporation of additional CI states from different symmetry blocks than the symmetry block of the MCSCF reference state into the MCRPA equations. For a 50 STO calculation on O2 molecule, our results for the lowlying vertical excitation energies are in excellent agreement with experiment and with largescale CI. Oscillator strengths, frequency dependent polarizabilities, and the energy weighted sum rule are also reported. Copyright 1981 John Wiley & Sons, Inc.