Spectroscopic studies of5d3/2nd1D0,2autoionization lines of barium under collision with rare gases

Abstract

The spectroscopic behavior of 5${d}_{3/2}nd$ (${}^{1}\phantom{\rule{-0.16em}{0ex}}$${D}_{0}$ and ${}^{1}\phantom{\rule{-0.16em}{0ex}}$${D}_{2}$) autoionizing Rydberg series of barium was studied under collision with rare gases. The series members from $n$ $=$ 8 to $n$ $=$ 64 were observed using two-photon excitation of the two valence electrons in the 6${s}^{2\phantom{\rule{0.16em}{0ex}}1}\phantom{\rule{-0.16em}{0ex}}$${S}_{0}$ ground state of barium. The barium vapor was produced in a heat-pipe-like oven, and a tunable dye laser pumped by an excimer laser was used as the excitation source. The obtained spectral data have Beutler-Fano profiles. These spectral lines were investigated when inert gases Ar, Kr, and Xe at different pressures were introduced into the oven as perturbing gases. The collision-induced line shifts were measured and the shift parameters for the even-parity 5${d}_{3/2}nd$ ${}^{1}\phantom{\rule{-0.16em}{0ex}}$${D}_{0}$ and 5${d}_{3/2}nd$ ${}^{1}\phantom{\rule{-0.16em}{0ex}}$${D}_{2}$ ($n$ $=$ 8--35) autoionizing states were extracted from the data. The collision-induced change in the spectral line shape at different Xe pressure was also explored.