Date of Award
Doctor of Philosophy
This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe¯ and Ru¯. Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy.
Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons is interesting but difficult to analyze in detail because the angular momentum coupling generates a large number of possible terms resulting from the open d shell.
Our work reports on the first inner-shell photodetachment studies and absolute cross section measurements for Fe¯ and Ru¯. In the case of Fe¯, an important astrophysical abundant element, the inner-shell photodetachment cross section was obtained by measuring the Fe+ and Fe2+ ion production over the photon energy range of 48-72 eV. The absolute cross sections for the production of Fe+ and Fe2+ were measured at four photon energies. Strong shape resonances due to the 3p→3d photoexcitation were measured above the 3p detachment threshold. The production of Ru+, Ru2+, and Ru3+ from Ru¯ was measured over 30 – 90 eV photon energy range The absolute photodetachment cross sections of Ru¯ ([Kr] 4d75s2) leading to Ru+, Ru2+, and Ru3+ ion production were measured at three photon energies. Resonance effects were observed due to interference between transitions of the 4p-electrons to the quasi-bound 4p54d85s2 states and the 4d→εf continuum. The role of many-particle effects, intershell interaction, and polarization seems much more significant in Ru¯ than in Fe¯ photodetachment.
Dumitriu, Ileana, "Inner-Shell Photodetachment of Transition Metal Negative Ions" (2010). Dissertations. 554.