Spectra And Dynamic Properties Of Eu 4f⁷6p_3/2ns Autoionization Process

It is well known that the autoionization spectrum represents the total cross section of autoionization process,while the autoionization branching ratio?BR?and the angular distributions?AD?of ejected electrons from the autoionizing states mean the partial cross section and differential cross section of autoionization process,respectively.In this paper,the isolated core excitation?ICE?and velocity map imaging?VMI?technique are used to study the Eu 4f⁷6p_3/2/2 ns?n=7,8?autoionization spectra and the dynamic characteristics of autoionization process for the first time.The dynamic characteristics of autoionization process contain the autoionization BR and the AD of ejected electrons.First,the Eu atom is stepwise excited from the 4f⁷6s² ground state to the 4f⁷6sns Rydberg states through the 4f⁷6s6p intermediate states,then excited to the 4f⁷6p_3/2ns?n=7,8?autoionizing states with the ICE technique.Furthermore,in the three-step excitation process,the polarization direction of the laser is parallel or perpendicular to that of the electric field.Since the Eu 4f⁷6p_3/2 ns autoionizing states are unstable,they rapidly decay to the 4f⁷6p⁺_1/2,4f⁷5d⁺or 4f⁷6s⁺ionic states with electrons accompanied.At this time,the ionic signal of the autoionization process is detected to obtain the Eu autoionization spectra and the electron signal is investigated to study the autoionization BR and the AD of ejected electrons using the VMI technique.Then,the Eu 4f⁷6p_3/2 ns?n=7,8?autoionization spectra and the dynamic characteristics of autoionization process are discussed and analyzed in detail.The complex spectra of the4f⁷6p_3/2/2 ns?n=7,8?autoionizing states is carried out by reproducing their line shapes,from which the spectroscopic information,such as their level energy and line width,can be obtained.In addition,the autoionization BR and the AD of ejected electrons are also measured to observe their energy dependence and the relation with the autoionization spectra.Moreover,the population inversion of the ions are studied which will provide useful information for the future development of autoionization laser,and based on the AD following the variation of the photo energy,the experimental data can be used for the new quantum theory.