Role of coherence and time in the mechanism of dynamical symmetry breaking and localization

The formation of resonant photon emission following core electron excitation in symmetric systems is discussed within a time-dependent framework. The starting point of the discussion is an expression for the rate of photon or Auger electron emission intensity valid for general excitation light pulses and shapes of potential energy surfaces. The mechanism of dynamical symmery breaking via the excitation of symmetry breaking and localizing modes is illustrated by the example of a linear symmetric molecule, e.g., CO₂. It is shown that the decay rates are proportional to the population of a coherent superposition of the localized core states. The coherence of the decaying localized core states governs the population flow between the |Φ_u〉 and |Φ_g〉 symmetry adapted core states and determines the amount of total photon emission intensity recorded for a final state of definite spatial symmetry.