Observation of Pair Splittings in the Autoionization Spectrum of Ba

Abstract

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