[en] Today, an electron collisions experiment under the conditions of single collision in the ultra-low energy field from some meV to hundreds meV made possible to observe the each activated elementary process. Total cross section and differential cross section (DCS) are determined by ultra-low energy electrons from electron source of photoelectrons by photon radiation instead of filament of thermal emission. In this paper, the total cross section of CS₂ and CO₂, electron attachment cross section of ₆, electron dissociative attachment cross section of Cl₂, CH₃I and CCl₄, molecular ion dissociative recombination cross section of HD⁺ and HeH⁺ are explained by each measurement method. The present state of some ultra high-resolution photoelectron spectroscopy is stated by photoelectron spectrum of H₂O, elastic cross section and potential curve of HCl. (S.Y.)