Direct Observations of Relativistic Effects in Single-Electron Momentum Distributions in Xenon Outer Shells

The $5p_{\frac{3}{2}}$ and $5p_{\frac{1}{2}}$ one-electron momentum probability distributions in xenon, measured by means of the noncoplanar symmetric ($e$,$2e$) reaction, show clear and direct manifestations of relativistic effects. The momentum densities and branching ratios cannot be described by nonrelativistic wave functions, but they are in very good agreement with those given by Dirac-Fock wave functions.