Electron-impact excitation of theBa+ion

Crossed beams of ${\mathrm{Ba}}^{+}$ and electrons were used to measure the absolute emission cross sections for the ${\mathrm{Ba}}^{+}$ lines, 455.4, 493.4, 490.0, and 413.1+416.6 nm. Polarization fractions of the light were also measured. The data were analyzed to extract level excitation cross sections. The excitation cross section for the $6{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ level has a value 34.7×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at the 2.72-eV threshold, shows marked structure in the 3-10-eV interval, and decreases to 1.71×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at 747 eV. The polarization fraction for the 455.4-nm light exhibits pronounced oscillatory structure in the interval 3-7 eV. Excitation cross section for the $6{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$, $7{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$, and $6{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}+\frac{5}{2}}^{}{}_{}{}^{}$ levels have values at threshold of 20.0×${10}^{-16\mathrm{}}$, 5.4×${10}^{-16\mathrm{}}$, and 4.3×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$, respectively. Total uncertainties at a "high-confidence level" are about ±10% for the $6{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ and $6{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ cross sections. Uncertainties range around ±30% for the $7{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ cross section and ±20% for the $6{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}+\frac{5}{2}}^{}{}_{}{}^{}$. Measurements for the $6{}_{}{}^2{}_{}{}^{}P$ cross sections agree at high energies with the Coulomb distorted-wave calculation of Sheorey and Burgess. Measurements for the