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, $E_0$, of 15.6 and 17.6 eV) for equal energy sharing and the ${\theta }_{12}=\pi$ 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 $E_0=14.6\mathrm{}\mathrm{eV}$ 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.