Threshold double photoionization in argon

Double photoionization in the outer shell of rare gases by a single photon is an important manifestation of electron correlations. One specific aspect which has received much attention over the years is double photoionization in the vicinity of the double-ionization threshold. On the theoretical side, this attention is due to the possibility of deriving certain threshold laws without a full solution of the complicated three-body problem of two electrons escaping the field of the remaining ion. On the experimental side, the study of threshold phenomena always provides the challenge for mastering extremely difficult experiments. 

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