(e,2e)processes on atomic targets (Ne, Ar) and molecular targets (CH4, N2, CO2): Role of electron-nucleus scattering

Abstract

The momentum distributions of the recoil ions were measured for the single ionization of atomic targets (Ne, Ar) and of molecular targets (CH${}_{4}$, N${}_{2}$, CO${}_{2}$) at incident electron energies ranging from 80 to 220 eV by using the reaction microscope. It was found that there are a remarkable number of recoil ions with large longitudinal momenta, and the relative contribution of these ions for Ne ($e$, 2$e$) reactions decreases faster than that for Ar ($e$, 2$e$) reactions with the incident electron energy increasing. This observed feature can be qualitatively interpreted by the different effective potential of the target core experienced by the electrons. The appearance of the large longitudinal momentum recoil ions for CH${}_{4}$, N${}_{2}$, and CO${}_{2}$ ($e$, 2$e$) reactions indicates that the strong interaction between the electron and the component-atoms target core in the molecules plays a significant role in the single ionization of small molecular targets. Depending on the independent atom model, we can intuitively understand the characteristics of the momentum distributions of the recoil ions CH${}_{4}^{+}$, N${}_{2}^{+}$, and CO${}_{2}^{+}$, respectively.