Measurement of argon <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:mi>e</mml:mi><mml:mo>,</mml:mo><mml:mn>2</mml:mn><mml:mi>e</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math> differential cross sections in the perpendicular plane from 5 to 200 eV above the ionization threshold

New $(e,2e)$ differential cross-section measurements from argon are presented in the perpendicular plane, where incident electron beam is orthogonal to both detected electrons that map out a detection plane as their angles varied. data were obtained at energies 40 200 eV above ionization potential (IP), with scattered and ejected having equal energies. These compared previous 5 50 IP well theoretical calculations different models this energy range. A significant discrepancy between prediction of theory experiment was retested, new experiments confirmed results measurements. Additional spanning which show deep minimum cross section under these conditions. Results for evolution into intermediate-energy regime also discussed.