Theoretical and Experimental Spectroscopy of the S₂ SState of CHF and CDF: Dynamically Weighted Multireference Configuration Interaction Calculations for High-Lying Electronic States


Dynamically adjusting the weights in state-averaged multiconfigurational self-consistent field (SA-MCSCF) calculations using an energy-dependent functional allows the electronic wave function to smoothly evolve across the potential energy surface (PES) and correctly preserves differing asymptotic electronic-state degeneracy patterns.We have developed a generalized dynamic weighting (GDW) method to treat high-lying electronic states. To test themethod, a global PES was constructed for the S2 (B~) state of CHF (CDF),which lies nearly 31000cm-1 above theminimumof the ground state. The GDWmethodwas used to produce SA-MCSCF reference states for subsequent multireference configuration interaction (MRCI) calculations, whose Davidson-corrected energies were extrapolated to the complete basis set limit. Quantum mechanical vibrational energy calculations for CDF were performed using the fitted PES, and the predicted energy levels are in excellent agreement with an extensive set of experimentally determined (optical-optical double resonance) levels, with a mean unsigned error of only 12 cm-1.



Keywords and Phrases

Clusters; Complete basis set limit; Davidson; Electronic wave functions; Energy dependent; Energy level; Experimental spectroscopy; Multiconfigurational self-consistent fields; Multireference configuration-interaction calculations; Optical-optical double resonance; Quantum mechanical; Reference state; Vibrational energies; Band structure; Electronic states; Excited states; Ground state; Quantum chemistry; Simulated annealing; Sulfur compounds; Potential energy surfaces; Clusters; Dynamics; Excited States

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