Branching Ratios Of Autoionization From Eu 4f⁷6p_1/2nd Autoionizing States

The autoionization branching ratios from Eu 4f76p1/2 nd [J] autoionizing states to its different final ionic states have been investigated with the combination of the three-step laser excitation and the velocity-map imaging technique. In this experiment, the experimental photoelectron images are obtained, from which energy distributions of ejected electrons are achieved with the mathematical transformation. Furthermore, the energy dependence of the branching ratios is investigated within the autoionization resonances, by which population inversion is observed as an important characteristics.In this paper, the branching ratios of autoionization from 4f76p1/26 d autoionizing states with different J to the 4f76s+(9So), 4f76s+(7So)and 4f75d+(9Do) ionic states have been investigated comprehensively. The energy dependence and variations with the J value are also studied systematically. Although the branching ratios to the three states can be resolved and analyzed with the velocity-map-imaging technique, the fine-structures of the 4f75d+(9Do) state are failed to be resolved in the measurement. Both the autoionization spectra and the branching ratios for the 4f76p1/26 d autoionizing states manifest heavy configuration interaction between the 4f76p1/26 d and the 4f75 dnl autoionization series.Since the autoionizing states below the 4f75d+(7Do) ionization limit, the possible configuration interaction among these series, 4f76p1/26d[J] and 4f75d(7Do) nl, is expected. While, we chose the 4f76p1/27 d autoionizing states above the 4f75d+(7Do) ionization limit to study the branching ratios to more ionic states. Furthermore, the branching ratios of single-peak or double-peak structure autoionizing states have been measured.The line shapes of the autoionizing states can be exhibit the different line shapes in that interference effect between the two excitation paths. The branching ratios of the Fano type line shapes and the Lorentzian type have been investigated. Furthermore, The branching ratios of autoionization from 4f76p1/2(J=3)8d and 4f76p1/2(J=4)8d autoionizing states also be investigated.