Dissociative excitation of selenium atoms in collisions of electrons with $\mathrm{Se}_2$ molecules

The dissociative excitation of selenium atom by electron impact is investigated for the first time under conditions of narrow composition of molecular beam. The thermal destruction of heavy $\mathrm{Se}_n$ molecules is used to obtain a beam with prevailing $\mathrm{Se}_2$ molecule. Seventeen cross sections of dissociative excitation of SeI are measured at electron energy of $50$ eV. Possible reactions of formation of excited selenium atoms in $\mathrm{e}-\mathrm{Se}_2$ collisions are discussed.