Angular distributions and branching ratios of the electrons ejected from the Ba [6${\mathit{p}}_{1/2(3/2)\mathrm{}}$${\mathit{ns}}_{1/2}$${]}_{\mathit{J}=1\mathrm{}}$ autoionizing states

We describe the first comprehensive measurements of the energy distribution, branching ratios, and angular distributions of electrons ejected from Ba i [6$p_{1/2}$ ${}_{\mathrm{}(3/2)\mathrm{}}{}^{}{}_{}{}^{}\mathrm{ns}_{1/2}^{}{}_{}{}^{}$ ${]}_{\mathrm{J}=1\mathrm{}}$ states in their autoionization to the Ba ii 6s, 5d, and 6p ion states. These measurements are made using a stepwise laser excitation scheme, which results in excitation of only the bound part of the autoionizing states. Furthermore, the laser excitation of these autoionizing states through the spherically symmetric Ba i 6sns ${}^1$ $S_0$ intermediate states results in simplified electron angular distributions. We find that the Ba i [6$p_{1/2}$ ${}_{\mathrm{}(3/2)\mathrm{}}{}^{}{}_{}{}^{}\mathrm{ns}_{1/2}^{}{}_{}{}^{}$ ${]}_{J=1\mathrm{}}$ states autoionize predominantly to an excited state of the ${\mathrm{Ba}}^{+}$ ion. The interaction between the Ba i [6$p_{1/2}$ ${\mathrm{ns}}_{1/2}$ ${]}_{J=1\mathrm{}}$ and the Ba i [6$p_{3/2}$ ${\mathrm{ns}}_{1/2}$ ${]}_{J=1\mathrm{}}$ series manifests itself in the sharp variation in the electron asymmetry parameter β near the neighborhood of the interaction. We also present a simple analysis of our results incorporating the multichannel quantum-defect theory.