Energy and angular distributions of autoionization electrons and channel interaction effects for the Sr 5pns J=1 autoionizing series

A comprehensive experimental study of the energy and angular distributions of electrons ejected from the Sr 5$p_{3/2}$ ${\mathrm{ns}}_{1/2}$ and 5$p_{1/2}$ ${\mathrm{ns}}_{1/2}$ J=1 autoionizing states with n ranging from 10 to 20 has been performed using multistep laser excitation and time-of-flight electron spectroscopy. The branching ratios for autoionization to the available ${\mathrm{Sr}}^{+}$ ion cores have been determined as well as the asymmetry parameter, β, of the electron angular distributions. Both the branching ratios and the β parameters are constant across isolated autoionizing states. However, measured β values and branching ratios change sharply across the line profiles of those 5$p_{3/2}$ ${\mathrm{ns}}_{1/2}$ states which have strong localized interactions with 5$p_{1/2}$ ${\mathrm{ns}}_{1/2}$ and 5$p_{1/2}$ ${\mathrm{nd}}_{3/2}$ states. A consistent six-channel quantum-defect-theory model has been developed which enables us to reproduce quite well the level positions, the total autoionization rates, the branching ratios to different ${\mathrm{Sr}}^{+}$ ion states, and the angular distributions of the electrons ejected in the autoionization to the ${\mathrm{Sr}}^{+}$ 5$s_{1/2}$ and 5$p_{1/2}$ ion states.