The role of coherence and time in the mechanism of dynamical symmetry breaking and localization

The formation of resonant photon emission following core electron excitatio n 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 pulse s and shapes of potential energy surfaces. The mechanism of dynamical symme ry breaking via the excitation of symmetry breaking and localizing modes is illustrated by the example of a linear symmetric molecule, e.g., CO2. It i s shown that the decay rates are proportional to the population of a cohere nt superposition of the localized core states. The coherence of the decayin g localized core states governs the population flow between the \ Phi (u)> and \ Phi (g)> symmetry adapted core states and determines the amount of to tal photon emission intensity recorded for a final state of definite spatia l symmetry. (C) 2000 John Wiley & Sons, Inc.