Observation of Pair Splittings in the Autoionization Spectrum of Ba

Using a three-step laser-excitation process we have selectively excited each of the four autoionizing ${(6\mathrm{}{p}_j, 20s_{\frac{1}{2}})}_J$ states of barium although the ${(6\mathrm{}{p}_j, 20s_{\frac{1}{2}})}_{j\pm \frac{1}{2}}$ pairs are separated by less than their autoionization linewidth. The energy and linewidth of each of the states have been measured. The ${(6\mathrm{}{p}_{\frac{1}{2}}, 20s_{\frac{1}{2}})}_1$ state has an anomalous width which implies that it autoionizes primarily into excited ${\mathrm{Ba}}^{+}$ ${\mathrm{Ba}}^{+}\left(6\mathrm{}{p}_{\frac{1}{2}}\right)$ ions.