The spectra and dynamic properties of Eu [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] 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 (ED) 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 BR and AD are analyzed within the entire region of autoionization resonance. Based on the results of BR between [Formula: see text] and [Formula: see text] ionic states, the possibility of the population inversion is discussed.
Even-parity Rydberg and autoionizing states of lutetium by laser resonance-ionization spectroscopy
