Coherence Effects in Electron Emission by Atoms

Abstract

In experimental collision physics one obtains information by observing the changes of a system from some experimentally prepared initial state to some detected final state. This information is usually formulated in terms of transition probabilities. In order to obtain well-defined transition probabilities experimentally, one tries to define initial and final states as well as possible by the experimental setup. In an ideal case, initial and final states of the collision system are completely determined in the quantum-mechanical sense. The corresponding transition probability we denote by the symbol I if ; it contains all the information that can possibly be obtained on the transition. Usually, a transition i → f can proceed in “different ways,” or in the quantum-mechanical language, via different intermediate substates. Since the system evolves in such a case from a completely defined initial state, the state vector representing the intermediate state is a coherent sum of the substate vectors, and consequently the transition probability I if is a coherent sum, squared, of amplitudes belonging to the different intermediate substates.