ABSOLUTE TRIPLY DIFFERENTIAL (E,2E) CROSS SECTION MEASUREMENTS FOR H WITH COMPARISON TO THEORY

Absolute triply differential (e,2e ) cross section measurements are presented for H (for incident energies, E{sub 0} , of 15.6 and 17.6eV) for equal energy sharing and the {theta}{sub 12}={pi} configuration. Results of distorted partial wave calculations agree with the measurements; those of convergent close coupling calculations agree with the relative angular distributions, but are lower than experiment by factors of from 2 to 7. Relative experimental results for H for E{sub 0}=14.6 eV show a qualitative change in shape, which agrees with theory. Implications of the absolute experimental results for the range of validity of the Wannier threshold law are discussed. {copyright} {ital 1997} {ital The American Physical Society}