Interaction of the6p2S10broad resonance with5dndJ=0autoionizing resonances in barium

Abstract

We present even-parity autoionizing resonances in barium using two-step laser excitation via $5d6p$ ${^{1}P}_{1}$ intermediate level covering the energy region from the first ionization threshold to the $5d$ ${^{2}D}_{5/2}$ limit. The data are achieved using an atomic beam apparatus in conjunction with a time-of-flight mass spectrometer and a Nd:YAG pumped dye laser system. True line shape of the $6{p}^{2}$ ${^{1}S}_{0}$ autoionizing resonance at $44\text{ }850\ifmmode\pm\else\textpm\fi{}50\text{ }{\text{cm}}^{\ensuremath{-}1}$, its width $(980\ifmmode\pm\else\textpm\fi{}50\text{ }{\text{cm}}^{\ensuremath{-}1})$, and the absolute value of photoionization cross section $(185\ifmmode\pm\else\textpm\fi{}35\text{ }\text{Mb})$ are reported. A combination of parallel and perpendicular polarization vectors of the exciting and the ionizing dye lasers reveals unambiguous $J$-value assignments of the excited states. The interactions between the $6{p}^{2}$ ${^{1}S}_{0}$ broad feature with the $5{d}_{5/2}nd$ $J=0$ Rydberg series have been simulated using the phase-shifted multichannel quantum defect theory.