Absolute Elastic and Inelastic Differential Cross Sections for the Scattering of Low-Energy Electrons by Potassium

A new method for obtaining absolute differential excitation cross sections in low-energy electron-atom scattering is employed. The method utilizes certain of the kinematic properties of a recoiling-atom beam in an electron-atom crossed-beam configuration to distinguish between elastic scattering events and excitation to various atomic levels. Differential cross sections for elastic scattering and excitation of the $4p$ state of potassium are presented at 1.0, 3.0, 4.4, and 5.2 eV. A combined cross section for the $4s-5s$, $3d$ excitation integrated over a restricted angular range is also presented.