X-ray Spectroscopy and Pulse Radiolysis of Aqueous Solutions

• Main Author: England, Alice Heller
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: eScholarship, University of California 2011
• Subjects: Chemistry; Carbonic acid
• Online Access: http://www.escholarship.org/uc/item/8sn14153; http://n2t.net/ark:/13030/m50g3q4t

The interaction of radiation and matter plays a crucial role in studies of aqueous solutions. Depending on the type of radiation, it can either be used a probe or as a source of excitation. With X-ray spectroscopy, high-energy photons are tuned to excite core electrons, giving insight into electronic structure and the local chemical environment of both the solvent and solute. In pulse radiolysis, an accelerated electron beam is used as an excitation source to create transient radiolytic products. Here, I present detailed studies using both X-rays and electron beams to investigate aqueous solutions and phenomena.In Chapter 2, I discuss the probing of the pH-dependent aqueous carbonate system by soft X-rays. Spectral changes between carbonate, bicarbonate, carbonic acid, and carbon dioxide are analyzed by comparison with theoretically computed spectra. I also give an introduction to Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy and discuss experimental details for the design and employment of liquid microjets.Chapter 3 describes a variety of different projects aimed at expanding the capabilities of the X-ray absorption experiments. These new directions include characterizing free radicals in solution, developing a new detection technique, exploring X-ray induced damage to solid biomolecules, and potentially investigating unusual nitrogen compounds.In Chapter 4, I explore the interaction of high-energy electrons (8 MeV) with aqueous nickel (II) solutions. Pulse radiolysis combined with UV-visible absorption spectroscopy is used to investigate the kinetics of Ni 2+ with water radiolysis products. The rate constant for the solvated electron reaction with Ni 2+ is measured up to 300°C, and the electronic spectrum for the monovalent nickel ion is also recorded at high temperatures.