St. Catharines 2004
Technical Program


SS19:  Molecules to Planets: Infrared spectroscopy in geochemistry, exploration geochemistry and remote sensing 
Organizers / Organisateurs:  Penny King, Mike Ramsay, Gregg Swayze
Room / Salle:  AS 201

Date:  05/12/2004
Time:  8:40 AM
Presenter:  Carol J. Hirschmugl


Applications of storage ring infrared microspectroscopy and reflection-absorption spectroscopy to geochemistry and environmental science

Hirschmugl, C.J. University of Wiscosin-Milwaukee, Department of Physics and Laboratory for Surface Studies, Milwaukee, WI, USA, 53211, cjhirsch@uwm.edu

Infrared radiation extracted from a storage ring affords new opportunities for scientific exploration in the areas of geochemistry, geomicrobiology and environmental science. An introduction to the source properties of infrared radiation emitted from relativistically accelerated electrons in a storage ring will be presented. The most important of these properties is the brightness of the source. A bright source can deliver a higher density of photons onto a small (1 micron x 1 micron) sample at normal incidence than a lab based globar source, which is necessary to produce diffraction limited spatially resolved infrared images. Alternatively, this source can couple well to grazing incidence geometry for surface science experiments affording the opportunity to examine low frequency adsorbate-substrate vibrational bands.

Infrared (IR) images of single cells of the microalga Euglena gracilis have been measured using synchrotron radiation as a bright IR source. The distribution of lipids, proteins, chlorophyll, and carbohydrates with a few mm spatial resolution for individual algal cells have been obtained for the first time. A comparative chemical analysis was conducted on cells subjected to nutrient limitation and on their nutrient sufficient counterparts. Our results demonstrate the feasibility of using FTIR microspectroscopy for physiological studies.

The far- and mid-infrared broadband absorptions and discrete vibrations have been studied for water adsorbed on an epitaxial 2000 Angstrom Fe3O4(100) film using infrared synchrotron radiation.  Water on Fe3O4 represents an ideal example both since Fe3O4 is a prominent subsurface mineral (magnetite).  The present synchrotron-based infrared studies extend traditional IRAS measurements to below 400 cm-1 with noise levels of approximately .01% attainable in 100 seconds measuring time. In addition, these measurements are complemented by temperature programmed desorption measurements. Notably, three distinct cation adsorption sites are available on the reconstructed Fe3O4(100) surface: a tetrahedrally bonded Fe2+; a tetrahedrally bonded Fe3+; and an octahedrally bonded Fe3+. Molecularly adsorbed water is shown to sequentially fill these sites. In additon, adsorbed multilayers of water reveal large anti-absorption resonances in the infrared spectra for the molecular vibrations and the substrate phonons.