Spectra And Dynamic Properties Of Eu4f⁷6p_3/2nd Autoionization Process

The branching ratios of ions,the angular distributions of electrons ejected and the spectra from the Eu 4f⁷6p_3/2 nd（n = 6,7）autoionizing states are investigated with the velocity-map-imaging technique and the three-step three-color isolated-core excitation（ICE）technique.The relevant bound Rydberg states have to be detected first to populate the above autoionizing states.Then,the Rydberg states can be excited to autoionizing states through ICE method.With all preparations above,the branching ratios from the above autoionizing states to different final ionic states and the angular distributions of electrons ejected from these processes are measured systematically.At first,a two color three photon resonant ionization method is employed to detect the several 4f76 snd bound states in a given energy region.Then,the spectra of 4f⁷6p_3/2 nd autoionizing states are obtained by further exciting the 4f76 snd bound states.Electrons produced in the interaction region are focused by a suitable electron lens and impacted onto the PSD.The fluorescence from the PS is captured by the CCD camera and transferred to a computer for the further data analysis.Since the Eu 4f⁷6p_3/2nd and 4f⁷6p_3/2 nd autoionizing states are the two different autoionizing series,and the average energy of the latter is 2851.8 cm-1 higher than that of the former,so the obvious physical differences are expected.Additionally,the wavelength of the third laser for the excitation of the 4f⁷6p_3/2 nd autoionizing states has to be much shorter than that for the 4f76p1/2 nd autoionizing states,which is quite close to the shortest wavelength limit of the laser dyes.Therefore,not only do the related physical problems become more challenging,but also the experimental difficulty is greatly increased.Apparently,such a study is necessary as the Eu 4f⁷6p_3/2 nd autoionization series in the higher energy region can be revealed,and the application of the isolated-core excitation（ICE）technique can be expanded to the newly-found autoionizing states.Furthermore,the impact of laser polarization on the autoionization spectra of the Eu 4f⁷6p_3/2 nd states will be explored,which has only been done in the alkaline-earth atoms before.Finally,an assignment of J values to all the peaks in the autoionization spectra will be carried out by comparing their corresponding spectra obtained under different excitation paths,which is also a task with both expected and unexpected challenges.Finally,the similarities and differences of autoionization spectra,autoionizing decay branch ratio and ejection electron angular distribution in different polarization modes are discussed.Based on the above facts,taking n=6,7 for instance,the spectra,the BR and the AD of the 4f⁷6p_3/2 nd autoionizing states are systematically studied by the VMI technique and the ICE technique is regarded as a significant task.