The VMI Study On Branching Ratio Of Eu Atom Decayed From4f⁷6p_1/26d Autoionizing State

The investigation of the highly excited states of rare-earth atoms may not only reveal thecharacteristics of atomic structure and physical properties of complex atoms，but also providecritical tests to new theories of quantum mechanics；Meanwhile, these studies may haveextensive application prospects to the high-tech field, such as exploring new mechanism oflaser, developing nuclear power. As one of most complex rare-earth atom, Eu atom has ahalf-filled4f sub-shell, leading to a complicated spectrum and physical properties in its highlyexcited states. In recent years, both traditional detection method and velocity-map imagingtechnique have been used to explore the branching ratio of autoionization from the Eu4f76p1/28s states in few unpublished reports. However, the same is not true for the Eu4f76p1/2nd autoionizing states. On the other hand, both structure of level energies and relatedphysical properties of4f76p1/2nd autoionizing states are more complicated than the4f76p1/28sautoionizing states. More challenge is expected if one attempts to explore the branching ratioof autoionization from the4f76p1/2nd autoionizing states. Therefore, this thesis will investigatesystematically the branching ratio of autoionization from the4f76p1/2nd autoionizing states byemploying the velocity-map imaging technique.Firstly, the spectrum of autoionizing states4f76p1/2(J=3,4)6d of Eu atom is investigatedby using isolated-core excitation method. The atom is stepwise excited from the ground state4f76s28S7/2to the Rydberg states4f76s6d (8D5/2,8D7/2and8D9/2) via the intermediate state4f76s6p8P5/2using two dye lasers, then detect the autoionizing states by scanning the thirdlaser wavelength, analyze and interpret the complex structure and autoionizing configurationpossible interactions.Secondly, most of the electronic images obtained early are focus ineffective, so it leadsto the poor image resolution; while reducing the credibility of the experimental data. Since theresearch subject is autoionizing states4f76p1/2(J=3,4)6d, from which the level energiesstructure decayed are more complex, and the research recommends the focus effective morehigher. By using the Simion software to simulate the electronic images and give the bestvoltage，thus greatly improve image resolution, while excluding other experimental apparatusduring the experiment generated background noise. Scaling the intensity and position afterreceiving the electronic images, to further ensure the reliability of the experimental data，which these works above always played a important role to the thesis.Finally, the velocity-map imaging technology is employed to investigate systematicallythe dynamical process of ejected electrons from autoionizing states4f76p1/2(J=3,4)6d of Euatom. According to the total angular momentum and the conservation laws of energy, enableus to determine the final states of ions，and give its autoionizing decay branching ratio finally.By tuning the wavelength of the third excitation laser, the variation characteristic of thebranching ratio with the photon energy is observed. According to branching ratio of Eu atom decayed from4f76p1/2(J=3,4)6d autoionizing states, it not only enriches knowledge of thecomplex autoionizing states of Eu atom，also provides a theoretical basis for the application ofautoionizing laser.