Rules for Excited States of Degenerate Systems: Interpretation by Frozen Orbital Analysis

Abstract

This review addresses the rules for the ordering and the splitting of the excited states for the transitions between degenerate orbitals. First, the generality of the rules for the degenerate excitations is examined numerically by highly correlated methods for various types of systems, having D∞h, C∞v, Td, Oh, and Ih symmetries. Next, the qualitative interpretation of the rules for degenerate excitations is demonstrated by adopting the frozen-orbital approximation/analysis.