The Study On Highly Excited States Of Eu Atom With RIS And VMI Techniques

The spectra and dynamic properties of Eu 4f⁷6pnd autoionizing states are studied systematically with the resonance-ionization spectroscopy?RIS?and the velocity-map imaging?VMI?techniques.The RIS technique is utilized to obtain the spectra of Eu 4f⁷6pnd autoionizing states with the three-step excitation,while the VMI technique is used to detect the dynamic process of autoionization,from which the branching ratio?BR?of ions and the angular distribution?AD?of ejected electrons from Eu 4f⁷6pnd autoionizing states are achieved.Not only the energy levels,line width and line shape are obtained,but also the q-reversal phenomenon is observed in the autoionization spectra.The BR represents energy distribution of ions,by observing the radical information of the VMI image,while the AD,characterized by anisotropy parameters,reveals the differential cross section of autoionization extracted from the angular information of the VMI image.Furthermore,the variation of the BR and AD are analyzed within the entire region of autoionization resonance.Based on the results of BR between 4f⁷6s⁺and 4f⁷5d⁺ionic states,the possibility of the population inversion is discussed.Besides,The spectra of odd-parity states of Eu atom are studied systematically with two-photon ionization detection technique.The two-photon ionization detection technique is utilized to obtain the spectra of odd-parity states with the two-step excitation:the wavelength of the first step laser is fixed,while that of the last-step laser is scanned around the region of35500-35650cm^-1,36200-36600cm^-1 and 46650-46950cm^-1.The spectra characteristics in the energy region of 35500-35650cm^-1,36200-36600cm^-1 and 46650-46950cm^-1 are investigated,demonstrating the special lifetime of highly excited states within those energy regions.In this paper,three different excitation pathways are used,not only the energy levels,line width and line shape are obtained,but also the q-reversal phenomenon is observed in the odd-parity states spectra.Besides,through analysis the odd-parity states spectra of Eu atom,it is demonstrated that the possibility of 4f electrons are excited for the first time.