COHERENCE BETWEEN THE EXCITATION OF STATES WITH DIFFERENT ENERGIES

In recent experiments we have shown both in electron impact and in pho toionisation studies the possibility to determine coherences between t he excitation of states of different energies. In this paper the conse quences of applying coincident techniques to these experiments are dis cussed. In a coincidence experiment one has to choose, however, for lo wer energy resolutions in order to reach sufficient count rates. We pr esent an experiment which shows that these lower resolutions do not to tally obscure the formerly observed interference effects, thus proving the feasibility of a future coincidence experiment.