Branching ratio and angular distribution of ejected electrons from Eu 4f⁷6p_3/2ns autoionizing states

First, the Eu atom is excited from the 4f⁷6s²⁸S_7/2 ground state to the 4f⁷6sns Rydberg state via the 4f⁷6s6p intermediate state, then excited to the 4f⁷6p_3/2ns (n = 7, 8) autoionizing states with the isolated core excitation method. Then, the ejected electrons from the Eu autoionization process are detected by using the velocity map imaging technique to study the autoionization branching ratio and the angular distributions of ejected electrons. When the autoionization branching ratio is studied, the possibility of the population inversion is mainly discussed. This phenomenon can provide useful information for the realization of the autoionization laser. In addition, the impacts of the anisotropic parameters on the angular distributions of ejected electrons are discussed. Furthermore, at the different positions of Eu autoionization probability, the shapes of the angular distributions of ejected electrons are also discussed. (authors)