Emission cross sections of the Cd II spectral lines in e-Cd⁺-ion collisions

The absolute emission cross sections for the Cd II 226.5, 274.9, 257.3, 325.0, 231.3, and 219.5 nm lines have been measured by using a crossed-beam method of electrons and Cd II ground-state ions and a photon counting method. The electron energy region investigated was from the threshold energy (5.5 eV) for the excitation of the 5p ²P_1/2 resonance state to 20 eV. The peak value of the cross section for the resonance line (265.5 nm) is 1.3*10^-15 cm² near the threshold energy. The cross sections for the spectral lines originating from the Cd II higher states are smaller by one order of magnitude than that for the resonance line. However, the peak value of the cross section for the 325.0 nm line originating from the ionic Beutler state, 5s^{2 2}D_3/2, is comparable with that for the resonance line.