Absolute triple differential cross sections for the 3p ionisation of argon by electron impact

The triple differential cross sections for electron impact ionisation of argon on its 3p orbital are investigated for a primary electron energy near 8 keV. In a coplanar coincidence experiment, both ionisation electrons are analysed with respect to their energy and scattering angles. As in previous low-energy measurements, two lobes are found in the angular distribution of the slow ejected electron. The data are made absolute to an accuracy of better than 10%. This is done at high energy and large momentum transfer, K, by normalising to the impulse approximation Compton profile and assuming a cylindrical symmetry of the data about K. At high momentum transfer where the collision may be considered as a binary electron-electron process, the Ar 3p electron momentum distribution is determined and found to be in very good agreement with the Fourier transform of the Hartree-Fock-Clementi wavefunction.