Dissertation Defenses

Doctoral Dissertation Announcement

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Candidate: Ileana Dumitriu

Degree of: Doctor of Philosophy

Department: Physics

Title: Inner-Shell Photodetachment of Transition Metal Negative Ions

Committee:
Dr. Nora Berrah, Chair
Dr. Manuel Bautista
Dr. Thomas Gorczyca
Dr. John Tanis
Dr. Alex Aguilar

Date: Wednesday, August 18, 2010 2:00 p.m. - 4:00 p.m.
2202 Everett Tower

Abstract:
This dissertation 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.
This 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 3p3d 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. It appears that the Ru+ signal above the 4p threshold (over) arises from s-wave continua only, while the 4d resonances lie below the threshold. The role of many-particle effects, inter-shell interaction, and polarization seems much more significant in Ru¯ than in Fe¯ photodetachment.