ABSENCE OF INTERCHANNEL COUPLING IN ELECTRON MOMENTUM SPECTROSCOPY

We demonstrate that electron momentum spectroscopy (EMS), based on the high-energy (e,2e) reaction, can provide clean information on the ele ctronic structure of the target that is not obscured by interchannel c oupling in the ionization continuum. This is in sharp contrast to high -energy photoionization in which target states with different angular momentum, which are close in energy, are always mixed through intercha nnel coupling in the continuum. In atoms, in particular, the photoioni zation spectra of nl(l>0) subshells always have significant intensity due to admixture from the neighboring ns subshell. This mixing is show n to be negligible in electron momentum spectroscopy, a point we speci fically illustrate for the (e,2e) spectra of the argon M shell. [S1050 -2947(98)08409-1].