Angle-resolved electron-energy-loss study of core-level electron excitation in molecules: Determination of the generalized oscillator strength for the carbon 1s(2${\mathrm{\sigma }}_{\mathit{g}}$→2${\mathrm{\pi }}_{\mathit{u}}$) excitation in ${\mathrm{CO}}_2$

As part of a systematic, quantitative study of the angle dependence of core-level-electron excitation by electron impact, we have determined the generalized oscillator strength (GOS) for the carbon 1s(2${\mathrm{\sigma }}_{\mathit{g}}$→2${\mathrm{\pi }}_{\mathit{u}}$) transition in ${\mathrm{CO}}_2$. The experimental results were obtained at an impact energy of 1290 eV, in the angular range of 2°–14°, with an energy resolution of 0.9 eV. Theoretical values for the GOS were also obtained, using ab initio Hartree-Fock molecular wave functions and allowing for the relaxation of all the molecular orbitals in the determination of the excited-state wave function.