Photo-double-ionisation

Photo-double-ionisation involves the simultaneous ejection of two photoelectrons, from a target species, by a single photon of light. This process requires a strong interaction between the two ejected electrons: photo-double-ionisation experiments therefore provide unique information about electron correlations.

Experimentally, it is necessary to measure the two photoelectrons in coincidence; that is, they must be detected simultaneously. Thus the apparatus for photo-double-ionisation involves a pair of photoelectron analysers arranged symmetrically about the incident photon beam. In order to obtain the best possible energy resolution it is desirable to use threshold analysers for the detection of the photoelectrons, hence the technique may be referred to as “threshold photoelectron spectroscopy”.

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