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Fort Worth, TX 76129
Phone: (817) 257-7375
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Email:physics@tcu.edu

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by Kaoru Yoshida

Fall 2006 Seminar Information

Friday, December 1, 2006 at 1:30 p.m. in SWR 357
Refreshments will be served
The Pre-Dissertation Oral Examination will follow at 2:45

Robin Kinzer
Department of Physics and Astronomy Texas Christian University

Fourier Transform Infrared Spectroscopy of Transition-Metal Carbides

Research supported by the Welch Foundation Grant Number Y-1100

Sponsor: Dr. Graham

 

Friday, November 10, 2006 at 1:30 p.m. in SWR 357

Dr. Alex Weiss
The University of Texas at Arlington

Positron Annihilation Induced Auger and Gamma Spectroscopy

Abstract:

The annihilation of positrons with core electrons results in unique signatures in the spectra of Auger-electron and annihilation-gamma rays that can be used to make clear chemical identification of atoms in the environment of the positron at the time of annihilation. Because positrons implanted at low energies are trapped with high efficiency in the image-correlation well where they are localized just outside the surface it is possible to use annihilation induced Auger and Gamma signals to probe the surfaces of solids with single atomic layer depth resolution. In this talk we will report recent applications of Positron Annihilation Induced Auger Electron Spectroscopy (PAES) and Auger-Gamma Coincidence Spectroscopy (AGCS) to the study of surface structure and surface chemistry. Our research has demonstrated that PAES can be used to obtain Auger spectra with the extremely low background, and increased surface sensitivity and can thus provide new information regarding the composition of the top-most atomic layer. The applicability of PAES to the study of Se passivated Si surfaces and catalytically important surfaces of oxides and wide band-gap semiconductors will be discussed in light of recent measurements. We will conclude with a discussion of the use of Auger-Gamma and Gamma-Gamma coincidence spectroscopy for the study of surfaces at pressures closer to those found in practical chemical reactors.

Research supported by the Welch Foundation Grant Number Y-1100

Sponsor: Dr. Zerda

 

Thursday, October 12, 2006 at 2:00 p.m. in SWR 357

Dr. E. Jackson
The University of Texas M. D. Anderson Cancer Center

Advances in Biomedical Applications of Magnetic Resonance Techniques: From Anatomy to Function

Abstract:

Recent engineering advances in clinical magnetic resonance (MR) scanner subsystems have allowed the transformation of the state-of- the-art MR scanner from a means of providing exquisite anatomical information to a means of also providing quantitative assessment of tissue function.  Following a brief review of MR physics principles relevant to biomedical applications, this seminar will overview current functional MR techniques, including diffusion and diffusion tensor imaging for assessment of white matter tracts, blood oxygen level dependent assessment of neuronal function, dynamic contrast enhanced techniques for assessing changes in the microvascular environment, and MR spectroscopy techniques for non-invasive assessments of biochemical changes.

Sponsor: Dr. Ingram

 

Friday, September 8, 2006 at 1:00 p.m. in SWR 357
Refreshments will be served at 2:00 p.m. in SWR 313
The Dissertation Oral Examination will follow at 2:15

Dissertation:

Vincent Jobando
Department of Physics and Astronomy Texas Christian University

Positron Annihilation Spectroscopy Study of Rubber-Carbon Black Composites

BS, 1999, Moi University, Kenya

MS, 2002, Miami University, Ohio

Sponsor: Dr. Quarles

 

Friday, September 1, 2006 at 3:00 p.m. in SWR 357
Refreshments will be served at 2:45 p.m. in SWR 357

Dr. Gerhard Brauer
Institut für Ionenstrahlphysik und Materialforschung
Forschungszentrum Rossendorf, Postfach 510119, D-01314 Dresden, Germany

Characterization of ZnO single crystals by positron annihilation

Abstract:

Positron Annihilation Spectroscopy (PAS), based on radioactive positron sources, is now a well-established tool for the study of electronic and defect properties of bulk solids, whereas mono-energetic positron beams are needed to investigate thin films and surfaces. As an introduction, the application and basic physics behind PAS methods will be explained briefly. Zinc oxide (ZnO) is a potential semiconductor suitable for fabrication of visible and UV light emitters and detectors as well as high-temperature electronics. However, to achieve this goal, a full understanding of the role of lattice defects is needed as they largely control the optical and electrical properties. Here, a summary of our recent research results to identify lattice defects in ZnO single crystals will be presented which includes the application of radioactive positron sources, a mono-energetic positron beam, and also theoretical calculations. Finally, an outlook about future work will be given. This includes the construction of an accelerator-based and pulsed intense positron beam, and the study of ZnO nanorods.

Sponsor: Dr. Quarles