Research projects involving undergraduate students

Dr. Mellita Caragiu

I intend to work in three different, but complementary areas with the undergraduate students, so that I give students the opportunity to try out and decide upon which activity suits them best – experimental, theoretical, or computational physics.

Experimental research involving undergraduate students:

Updating the optics lab so that experimental work can be carried out at an appropriate level. The purpose will be to give students an opportunity to observe optical phenomena that are less intuitive. The students will have to set up the experiments themselves, therefore getting a correct understanding of how various optical components work. The experiments will use laser radiation and will explore concepts in image formation, spatial filtering, holography and speckles. This practical activity can be corroborated with a design of optical components using computer software commercially available. By trying to design a particular optical system that has a certain effect on light propagation, students deepen the theoretical knowledge acquired in class about image formation.

Students who got involved: Heather Buehler, Nathan Baxter (independent study), and the students enrolled in the Optics course
                                             Robbie Merrill, Debie Cox, Courtney Buckey

        Robbie’s “Bear with a fish” object became one of the nicest transmission holograms that we’ve obtained!

                                             Jason Field - arranged the display cabinet at the entrance of Meyer Building, showing three reflection holograms, and one transmission hologram;

                                             Angela Phares and Brock Prater 

See some pictures of the students working on the holographic set-up!

        Robbie preparing the solutions to develop the holographic plates   

Study of colloid
al crystals: in the same area of experimental research students are given the opportunity to explore other topics of interest, such as the formation of colloidal crystals (polystyrene hydrophobic microspheres in a solution of deionized water, helped by an ion exchange resin) and their geometrical structure (type of crystal, lattice parameter). The study is done by employing He-Ne (visible) laser light, and applying diffraction techniques otherwise typical to X-ray studies of "ordinary" crystals. The work involves both experiment and calculations, with fairly sophisticated theoretical ideas as a guiding infrastructure.     
Students involved: Courtney Buckey, Robert Merrill, Tom Manuszak, Christina Leidel, Matthew Katschke, Nathan Baxter, Tyler Betts     

Link to the power point presentation about colloidal crystals.
The results of this research have been communicated at several physics meetings - see a list of them.

The theoretical
research involves the study of various problems at the interface between physics and mathematics. Such problems usually arise in the fields of analytical mechanics, quantum mechanics, statistical mechanics. This activity requires some knowledge of differential equations and linear algebra. The work employs the MAPLE computer package for analyzing more difficult equations.
Students who got involved: Robert Clark and Hanna Wagner 

Link to the power point presentation of the "pendulum problem".

Solid state computational physics
: more precisely, the investigation of the actual position of adsorbed atoms on various surfaces.

Starting in the early 1970s, there has been a continuous interest in the field of surface physics. The interest is legitimate due to the role that surfaces play in technological applications and much improvement is expected once the processes that occur at surfaces are understood.
It is for the purpose of a detailed knowledge of the interfaces at the atomic level, that the LEED (Low Energy Electron Diffraction) technique is extensively used in the study of solid surfaces. The technique has the capability to provide the coordinates of the surface atoms, facilitating the understanding of the interaction between these atoms and, ultimately, helping one explain and predict the macroscopic properties of the materials.
In principle, the LEED technique consists of a diffraction experiment that provides the raw experimental data. The data is consequently analyzed, so that the information about the atomic coordinates is extracted. The way that structural information is obtained is by a comparison between the experimental data and calculated, theoretical data that correspond to models of the surface under study imagined by the analyst. The theoretical data are a result of complicated computations that use computer programs developed through the efforts of many physicists.
Working on a problem such as resolving the structural parameters of solid surfaces gives the undergraduate students the opportunity of learning a lot about solid state physics, with emphasis on surface aspects, as well as the satisfaction of being able to obtain new results, sometimes unpredictable. The computer programs to be used require some computer knowledge that is usually acquired during the freshman year by most students.

Two particular surfaces have been investigated recently: 
I.  K adsorbed on clean Pb(111), forming a (√ 3x√ 3)R30° overlayer,
               -   results presented in a poster
at the OSAPS Meeting, Wayne State University, March 31-April 1, 2006:

                   Low-Energy Electron Diffraction Study of the Adsorption Geometry for Pb(111)-(√ 3x√ 3)R30°-K
                   Authors:  1Christopher Lemon,
2F.M. Pan, 1M. Caragiu, 2Nicola Ferralis, 2Renee D. Diehl

                   1Department of Physics and Astronomy, Ohio Northern University, Ada, OH 45810, USA 
Department of Physics and Materials Research Institute, Pennsylvania State University, 104 Davey Laboratory, University Park, PA 16802, USA

II.  and the clean, stepped surface Cu(511),
               -  preliminary results presented in a poster at the OSAPS Spring Meeting, Eastern Michigan University, May 4-5, 2007:

Low-Energy Electron Diffraction Investigation of the Cu(511) Stepped Surface
1Christopher M. Lemon, 1Mellita Caragiu, 2Renee D. Diehl, 2Kelly J. Hanna, 2Hsin I. Li, 2Rundong Wan

Student involved: Christopher Lemon

         Chris presenting the poster at the OSAPS meeting, May 2007

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