Experimental electron energy-loss spectra and cross sections for the5S2→5Po2transition in Cd ii

Experimental energy-loss spectra for excitation of the $5{}_{}{}^2{}_{}{}^{}S\to 5{}_{}{}^2{}_{}{}^{}P_{}^o{}_{}{}^{}$ transition in Cd II by electrons have been observed for the first time. Differential scattering cross sections are reported from spectra obtained at 75-eV electron energy. Comparisons are made to experimental results for the ${}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ integral excitation cross section from absolute emission measurements on the 214.4-nm (${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$) transition, to theoretical results for the analogous $4{}_{}{}^2{}_{}{}^{}S\to 4{}_{}{}^2{}_{}{}^{}P_{}^o{}_{}{}^{}$ transition in Zn II, and to semiempirical calculations in the Gaunt-factor approximation. A detailed description of the crossed (90°) electron-beam—ion-beam apparatus is given, and the method of conversion of scattering intensity to absolute cross section is discussed.