(e,2e) spectroscopy of H2O-separation energy spectra and valence orbital electron momentum distribution

The noncoplanar symmetric (e,2e) reaction has been applied to H2O at 1200eV and 400eV. By keeping the energies of the two emitted electrons fixed (and equal) and varying the incident energy, separation energy spectra are obtained in the valence region. In addition to the four prominent peaks at 12.7eV, 14.8eV, 18.7eV and 32.4eV, corresponding to the ejection of electrons from the 1B1, 3A1, 1B2, and 2a1 orbitals respectively, other structure extending up to 50eV is observed. Most of this structure can be assigned to the 2a1 orbital. Electron momentum profiles are measured for the above transitions. The momentum distributions are energy independent, in agreement with the plane wave model. They are compared with plane wave calculations using for the overlap functions between the target ground state and final ion states either simple SCF orbitals or overlap amplitudes calculated directly using the propagator formalism. The latter overlap functions include the effects of core relaxation and pair correlations, and they are in much better agreement with the data. The momentum profile for the ground state transition (1b1) is, however, not well described by either theory. The data show a greater probability of having low momentum electrons, corresponding to an increased electron density far from the nuclei. (author)