UofL

Research Interests in Physics at the University of Louisville




The Physics Department has active research programs in a large number of different areas. All our faculty are research active; many of their research programs are externally funded.



  Astrophysics

 The Physics Department operates Moore Observatory, located at the Horner Wildlife Sanctuary in nearby Oldham County. A computer-controlled 0.5 meter telescope, fiber optically coupled spectrograph, and cryogenic CCD camera are employed to produce photometric atlases of stellar spectra. A fully automated, wide field, spectral imaging camera is also being developed. The new instrument is being used at this site and at remote locations to investigate physical processes in comets and low surface brightness emission nebulae. Observational data from the observatory are archived and processed with a network of unix workstations at the observatory and on Belknap Campus.

     We study various aspects of observational cosmology, including quasar absorption lines, large scale structure and high redshift galaxies, proto-planetary disks, and the interstellar medium.  These studies are carried out using a multi-wavelength approach, from X-rays to the infrared.

 

 

Faculty

 

John F. Kielkopf, Ph.D.  (The John Hopkins University)

Gerard M. Williger, Ph.D.  (Cambridge University)

 

Publications

  1. Lyman beta in a laser-produced hydrogen plasma: the 1150 Å collision induced satellite, J.F. Kielkopf, N.F. Allard, Spectral Line Shapes, 13 (2004).
  2. Laboratory Detection of the Lyman beta 1150 Å Quasi-Molecular Satellite seen in Far Ultraviolet Spectroscopic Explorer Observations of the White Dwarf G226-29, J.F. Kielkopf, N.F. Allard, J. Huber, The Astrophysical Journal, 611, L129-L132 (2004).
  3. The D/H Ratio in the Interstellar Medium toward the White Dwarf PG0038+199, G.M. Williger, C. Oliveira, G. Hebrard, J. Dupois, et. al., Astrophys.Journal  625 (2005).
  4. The Low-Redshift Lyman Alpha Forest toward PKS 0405-123,  G.M. Williger, S.R. Heap, R. J. Weymann et. al., ApJ, (2005).

 



  Atomic and Molecular Physics

Low energy collisions involving neutral excited states of hydrogen are being studied in research sponsored by the U.S. Department of Energy, Chemical Sciences Division. High energy pulsed infra-red and ultraviolet lasers are used to photodissociate small molecules, generate negative ions, or create a dense gas of atomic hydrogen and its molecular ions. Emission spectroscopy, laser-induced fluorescence with tunable dye lasers, and four-wave mixing laser absorption spectroscopy are applied to observe radiative emission of H+H, H+0, and H+Al atomic collisions. This experimental work is coordinated with work on the theory of spectral line broadening, neutral atom interactions, and modeling of plasma processes (Kielkopf).

In our other experimental effort, we produce a molecular beam of atoms or very small molecules in a high vacuum chamber, and apply the techniques of pulsed or c w laser spectroscopy. We study interactions and decay processes of doubly-excited Rydberg states of, for example, H2 or Mg. Research instrumentation includes computer-controlled dual dye laser systems, an ArF excimer laser, two synchronized YAG lasers, a five meter focal length vacuum ultraviolet spectrometer, and dedicated UNIX workstations (Kielkopf).

Theoretical research has been directed toward developing a perturbative formulism for atomic states, which are linear combinations of several configurations. In this way the largest correlation effects can be built into a many-electron problem from the beginning and perturbation theory used only for effects that are genuinely small. Also, since molecular wavefunctions that disassociate properly generally consist of several electronic configurations, such a multi- dimensional formalism is necessary to calculate molecular disassociation and charge transfer processes. A calculation of the correlation energy of the beryllium atom has been implemented using this approach and other calculations are in progress to calculate transition probabilities. Recent calculations have extended this atomic work to dynamical molecular processes (Morrison).

Faculty

 
            John F. Kielkopf , Ph.D.  (The John Hopkins University)

            John C. Morrison, Ph.D.  (The John Hopkins University)

 

Publications

  1. Theoretical study of the Lyman Gamma line profile of atomic hydrogen perturbed by collisions with protons, N.F. Allard, J.F. Kielkopf, G. Hébrard, J.M. Peek,  European Physical Journal, D 29, 7-16  (2004).
  2. Far Ultraviolet Spectroscopic Explorer Observations of G226-29: First Detection of the H2 Quasi-molecular Satellite at 1150 Å., N.F. Allard, G Hebrard, J. Dupuis, P. Chayer, J.W. Kruk, J.F. Kielkopf, and I. Hubeny, Astrophysical Journal Letters, 601, L183-L186 (2004).

 



  Condensed Matter Physics

The experimental and theoretical efforts in condensed matter physics at the University of Louisville deal with a wide range of solid state phenomena.  Active research is presently being carried out on catalytic materials, ferroelectric crystals, mixed crystals, polycrystalline and amorphous solids, and a variety of organic compounds and super-conductors.  Many of these projects are related to important practical applications as well as more fundamental questions concerning the properties of matter.

Our solid state experimental group uses the techniques of nuclear magnetic resonance (NMR), and positron annihilation studies (PAS). In the NMR work, nuclei having spin-dipole and quadruple moments are used to probe the electric and magnetic fields of solids. The electric field at the site of the nucleus is especially sensitive to the properties of the valence and bonding electrons. So these experiments produce results of both physical and chemical importance. The NMR research has been directed principally to understanding in detail how the lineshapes obtained by the absorption and dispersion modes are related to the electric quadrupole and magnetic dipole interactions for polycrystalline and amorphous solids. (France)
The molecular dynamics/transport, phase behavior, as well as the emerging novel physical phenomena and applications under nanoconfinement are studied in a variety of novel materials.  In parallel, we develop NMR and MRI methods such as novel nuclear spin -lattice relaxation filter, fast imaging sequences, and simultaneous multi-dimensional diffusometry (Tang, ).

In a solid medium, positrons are thermalized quickly and annihilate with electrons in the material. For this reason, PAS has been employed as a micro-probe for studying electronic structures of a great variety of substances. In our department, this technique has been applied to investigate electronic properties of superconductors, catalysts and some organic polymers. The positron laboratory is equipped for performing angular correlation, Doppler broadening and positron lifetime measurements. Studies of high Tc superconductors are also in progress with techniques including I-V characteristics, thermoelectric power, magnetic susceptibility and tunnelling microscope (Huang).

The research interests of the Condensed Matter Theory Group focus on the development of real-space methodologies to predict structures, electronic, and vibrational properties of systems with low symmetry such as clusters, incommensureate systems, alloys, and vicinal surfaces. Theoretical approaches that are currently used are based on real-space green's function, molecular dynamics, and real-space tight binding LMTO calculations. Other areas of active research include phase transitions at surfaces such as reconstruction, melting, and pre-roughening phenomena (Jayanthi, Liu, Wu).

Due to their potential technological applications, there has been an increased interest in molecular films. Applications in optical and electronic devices, electroanalytical chemistry, and biological interfaces illustrate the intense attention on organic and biological thin films in the monolayer and submonolayer regimes. To fully exploit the technological possibilities offered by molecular films, a number of scientific problems need to be addressed. Among them is the relationship between structure in molecular assemblies and the corresponding chemical and biological properties. Investigation in molecular films requires experimental tools able to perform in-situ non-destructive analysis with the high sensitivity needed for submonolayer detection. Our research focus on novel analytical tools based on integrated optics and surface waves for research in biomolecular films and interface phenomena, on the spectroscopic investigation of the physical/chemical properties of biomolecular films, and on the integration of nano-structured photonic devices with molecular assemblies for selective and sensitive transduction in chemical and biological materials. ( Mendes)

Other experimental studies involve synthesis, characterization, device fabrication, and property measurements of various nanostructures including carbon nanotubes, semiconducting nanowires, and 3-D colloidal crystals (opals). Pulsed Laser  Vaporization, Chemical Vapor Deposition (including RF plasma, Hot filament, Vapor transport reaction),  Template directed growth are used for nanowire synthesis. HRSEM, HRTEM, Micro Raman, XRD, EDX are routinely used for material characterization. E-beam lithography, photolithography, wire bonding are used for device fabrication. Electrical transport properties are studied by measuring electrical resistivity, thermal conductivity, and thermo electric power in the temperature range 10-500 K and magnetic fields up to 3 Tesla (Sumanasekera).

Faculty

 

            Peter W. France, Ph.D. (Wayne State University)

            William C. Hoston, Ph.D. (Massachusetts Institute of Technology)

Wei-Feng Huang , Ph.D. (University of Virginia)

            Chakram S. Jayanthi, Ph.D. (Indian Institute of Technology, Delhi)

            Shudun Liu, Ph.D. (Rutgers University)

            Sergio Mendes, Ph.D. (University of Arizona)

            P.J. Ouseph, Ph.D. (Fordham University)

            Gamini U. Sumanasekera, Ph.D. (Indiana University)

Xiaoping Tang, Ph.D. (Northwestern University)

            Shi-Yu Wu, Ph.D. (Cornell University)

 

Publications


1.   Electrical conductance of carbon nanotori in contact with single-wall carbon nanotubes, Y.Y. Chou,G.Y. Guo,  L. Liu, C.S. Jayanthi, S.Y. Wu, Journal of Applied Physics, 96, 2249-2253 (2004).

  1. Stability and Mechanical Properties of Silicon Nanowires, S. Liu, C.S. Jayanthi, S.Y. Wu, Physics Review B, (2004). 
  2. Phonon Spectromicroscopy of Carbon Nanostructures with Atomic Resolution, L. Vitali, M. Burghard, M.A. Schneider, L. Liu, C.S. Jayanthi, S.Y. Wu,  Physics Review Letter, 93, (2004).
  3. Confined phonons in Si nanowires, K. W. Adu , H. R. Gutierrez , U. J. Kim , G. U. Sumanasekera , P. C. Eklund,  American Chemical Society, 49(2), 885-886 (2004).
  4. A 13C  NMR Study of the Molecular Dynamics and Phase Transition of Confined Benzene inside Titanate Nanotubes”, Tang, X.P., Wang, J.C., Cary, L., Kleinhammes,  Y. Wu, Journal of American Chemical Society 127, 9255 (2005).
  5. Synthesis of Gold Nanorod/single-wall carbon Nanotube Heterojunctions Directly on Surfaces, A.J, Mieszwska, , R. Jalilian, G. Sumanasekera, G., Zamborini, Journal of the American Chemical Society, 127 (31): 10822 (2005).
    6.
  6. Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution based on the Maximum Entropy Method. Runge, A. F; Saavedra, S. S.; Mendes, S. B. Journal of Physical Chemistry B (2006) 110(13), 6721-6731.
  7. Order Parameters and Orientation Distributions of Solution Adsorbed and Microcontact Printed Cytochrome c Protein Films on Glass and ITO and their Relationship to the Rate of Electron Transfer. Runge, A. F; Mendes, S. B.; Saavedra, S. S. Journal of Physical Chemistry B (2006) 110(13), 6732-6739.




High Energy Physics

 The University of Louisville is a member of BaBar, an experimental high energy physics collaboration working with a large, general-purpose electron-positron collider detector at .  The experiment runs in the PEP-II storage rings at the Stanford Linear Accelerator Center (SLAC).  Currently, the University of Louisville HEP group is investigating probes of QCD in quark and gluon jets and searching for rare CP-violating decays of the B-meson. This work involves extensive software development. Analysis of high energy deep inelastic lepton-nucleon scattering data is also in progress, as is planning and software development for the future International Linear Collider collaboration (Brown, Davis).

   

Faculty


            David N. Brown, Ph.D. (Purdue University)

Christopher L. Davis, Ph.D. (Oxford University)

 

Publications

1.    Study of  Decays: Measurement of the Ratio of Branching Fractions and Search for Direct CP Violation, B. Aubert, D. Brown, C. Davis and BaBar Collaboration, Phys. Rev. Lett., 92, 241802 (2004).

2.   Measurements of CP-violating Asymmetries in  Decays, Phys. Rev. Lett. ,93, 131805 (2004).

3.   Search for the Decay  B. Aubert, D. Brown, C. Davis and BaBar Collaboration, Physics Review, D69, 091503 (2004).

4.   Limits on the Decay Rate Difference of Neutral-B Mesons and on CP, T, and CPT Violation in B0-antiB0 Oscillations, B. Aubert, D. Brown, C. Davis and BaBar Collaboration, Physics Review, D70, 012007 (2004).



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