Inner-Shell Excitations of 2p Electrons of Argon Investigated by Fast Electron Impact with High Resolution

Electron energy loss spectra of inner-shell excitations of 2p electrons of argon are measured at an incident electron energy of 2500 eV and scattering angles of 0° and 4°. The dipole−forbidden transitions of 2p_3/2^-14p and 2p_3/2^-15p are observed in the measured spectra and assigned based on the calculations of the Cowan code. The positions and line widths for the excitations of 2p_3/2^-1nl and 2p_1/2^-1 nl(n≤5) of argon are determined. The present results show that the line widths of the electric quadrupole transitions of 2p_3/2^-14p5/2+3/2₂ and the electric monopole one of 2p_3/2^-14p1/2₀ are less than those of the dipole-allowed transitions.