George Hess
Research interests
About me
Monolayer films of simple molecules adsorbed on a graphite surface offer a unique opportunity to study phase transitions and other properties in quasi-two-dimensional systems, and, as more layers are added, the transition to three dimensions. We have been studying such films using an ellipsometric technique, which measures the change in polarization of light reflected obliquely from the graphite surface. This provides a measure of changes in thickness of a transparent film with a remarkable precision of 0.1 to 0.01 molecular layer, using a surface area of a few square mm. This work has revealed behavior such as sharp layer-by-layer growth of certain liquid films many degrees above their bulk melting points; a complex series of re-orientation transitions in solid oxygen multilayers; and evidence for a "pre-roughening" transition at the free surface of argon, krypton, and xenon crystals. The addition of infrared reflection absorption spectroscopy provides additional information on films of molecules with strong IR-active vibrational modes. We have used this to study the orientation of C2F6 molecules in various monolayer and bilayer phases. This technique is particularly useful with of binary mixture films, which we are currently studying. For instance it provides a rather direct measure of solubility in the monolayer and even evidence on the distribution of molecules in the solution.
I received a Ph.D. from Stanford University in 1967 with a thesis on rotation of superfluid helium. Since 1968 I have been on the faculty at the University of Virginia, apart from sabbaticals at the Univesity of Washington (1979-80) and Penn State (1994-5). Initially my students and I studied flow properties of superfluid helium in channels of various geometries. Since the mid-1980's we have studied primarily the properties of layers of simple molecules adsorbed on a clean graphite surface, using ellipsometry and more recently infrared absorption.
Petros Thomas
Research interests
About me
My research interest, in general, is adsorption, growth and two-dimensional phase-transition studies of atoms, molecules, and thin films on crystalline surfaces using optical techniques. These studies provide information about energetics, phase-diagrams, isotherms, growth modes, and phase transitions of two-dimensional systems such as: solid ⇔ liquid ⇔ gas, commensurate ⇔ incommensurate, structural (e.g., triangular ⇔ rectangular), wetting ⇔ non-wetting, order ⇔ disorder transitions. Currently, we are studying adsorption, growth and phase transitions of CF4 , CF3H, and CF3Cl on a highly oriented pyrolytic graphite (HOPG) surface using a polarization-modulation ellipsometry (PME) technique and Fourier transform infrared reflection-absorption spectroscopy (FTIRAS). The PME is a reliable and powerful technique to detect coverage from sub-monolayer up to ten layers and into the bulk region. The FTIRAS has capabilities in determining any changes in orientation of molecules on the surface during changes of thermodynamic parameters. Moreover, the FTIRAS provides us with adsorbate specificity on the surface during studies of mixtures of gases.
I received a PhD degree from the University of California at Davis in 2004. My dissertation work was on novel optical studies of sputtering, growth, and diffusion on metal surfaces. I held a lecturer position at the University of California in 2004-05. I joined the University of Virginia as a postdoctoral researcher since November of 2005.
Dan Velazquez
Research interests
About me
Anything which piques my interest and helps me on my way. Eventually I plan to teach Physics at a Military School, so I am taking physics education classes next semester.
I graduated from West Point in '94 with a Bachelors Degree in Chemistry. After being stationed in Germany, Bosnia and Texas, I returned home to the USA with my wife. The military considered a well earned break was necessary so they sent me to grad school to get a Masters in Physics from U.Va. Although... I would rather be in the field than studying Quantum!
George Michael Shifflett
Research interests
About me
For a number of years Mike has participated in various aspects of research in this lab, including data acquisition and analysis, during summer breaks from his teaching responsibilities
Mike graduated from George Mason University and earned his MS and Ph.D. degrees at UVa, doing experiments on dissipation in superfluid helium flow and depression of the superfluid fraction by velocity. Since then he has taught physics and astronomy on the faculty of Madisonville Community College in western Kentucky
Michael Grogan
Research interests
About me
My main interests currently lie in computational physics, a quickly developing field which is being used in many different areas. One of my specific interests lies in developing algorithms for data analysis, a specific focus of the computational courses I am taking next year. I am also interested in networking/communications and website design.
I'm a fourth year physics student from the University of Bath, England. I participated in an exchange program here at U.Va last year and enjoyed it so much that I wanted to stay for the summer. I am a keen photographer and I have enjoyed taking snaps of the wonderful scenery and wildlife in and around the area, some of which can be seen on my website.
John Liljegren
Research interests
About me
I am interested in the computational realm of physics, but I can't say for sure where I'll be in a few years.
Currently I'm in my third year at UVA, double-majoring in physics and math with a minor in computer science. I plan on attending graduate school in physics or math, probably with computer science applications.
Summer '06 Research
