UGA Physics and Astronomy | Departmental Research Facilities

There is a cluster of 20 Athlon 800 and 850 Mhz PC's, "The Klingon Bird of Prey", running FreeBSD utillized as a 20 node parallel machine. This facility is devoted to the research in computational astrophysics and focuses on the simulation of stellar and planetary atmospheres. UGA is the "home base" of the PHOENIX group which develops and maintains the PHOENIX general-purpose stellar/planetary model atmosphere computer code. The first stage was a 10 node cluster in October 2000; as a second stage, 10 more nodes were added in December 2000. For more information, visit "The Klingon Bird of Prey" web site.

The CSP operates a wide variety of modern computing facilities. These include a multiprocessor SGI O200 plus about a dozen other Unix based Scientific Workstations and about twenty high performance PC procssors running the Free BSD operating system. The CSP makes extensive use of the high performance computing facilities in the central university operations center. These platforms include a 40 Processor distributed memory IBM SP supercomputer and a 24 processor symmetric multiprocessor (shared memory) SGI Origin 2000 supercomputer.

The Department houses a state-of-the-art chemical physics laboratory with two molecular beam machines equipped with special time-of-flight mass spectrometers which provide mass as well as velocity information for the detected species. The laser systems consist of several Nd:YAG pumped dye lasers as well as a single mode infra-red optical parametric oscillator (OPO). They cover the wavelength range from the ultra-violet through the visible to the near infrared (< 4mm). The pulsed laser output is sufficiently high to initiate resonant multiphoton ionization in atoms or molecules which are subsequently analyzed in the mass spectrometer.

The combination of molecular beam techniques with laser spectroscopy provides a unique approach to the experimental study of the molecular reaction dynamics relevant to combustion or atmospheric processes. These processes are studied through counterpropagating molecular beam scattering or through infrared-ultraviolet double resonance experiments.

We have an Intervac Gen II Mod molecular beam epitaxy (MBE) system for the deposition of thin films and nanostructures. This system is equipped with six sources, four of which can be used simultaneously during the growth process. For the deposition of dielectrics such as CaF₂ the system has been modifed to incorporate high temperature sources. By changing the sources, III-V semiconductor heterostructures can also be grown. This system is equiped with in situ reflection high energy electron diffraction (RHEED) and reflectometry systems for obtaining surface information during the deposition process.

We have a wide range of continuous working and pulsed laser facities that range in wavelength from the far infrared (CO₂ pumped superadiant lasers) to the ultraviolet (excimer laser). Our pulsed laser facilities include: Q-switched Nd:YAG pumped dye lasers (ns), Modelocked Nd:YAG pumped dye lasers (ps), a modelocked Ti:Sapphire laser (fs), and an short pulse excimer laser (2.5 nsec). We also have actively stabilized single frequency lasers that give spectral coverage from 280-1000 nm with 1Mhz bandwidth. For high resolution infrared spectroscopy, a tunable lead salt diode laser system is available. In addition to laser facilities we have extensive detection facilities such as high resolution single and double monochrometors, photon counting systems and transient digitizers. A wide range of cryogenic facities are also in place including a 9 Tesla superconducting magnet system.

The Physics and Astronomy Department is a founding member of the Southeastern Association for Research in Astronomy (SARA). This consortium consists of: Florida Institute of Technology, East Tennessee State University, Valdosta State University, University of Georgia, Florida International University, and Clemson University. The SARA consortium, the only consortium of its kind in the Southeastern United States, operates a 0.9-meter telescope at Kitt Peak National Optical Astronomical Observatories (NOAO). The telescope is operated remotely over the internet from the SARA home institutions.

The Department recently acquired a scanning probe microscope for surface analysis and biological imaging. The instrument, a Digital

Instrument Dimension 3100 atomic force microscope, can be operated in several modes, including contact and tapping atomic force microscopy (AFM), scanning tunneling microscopy (STM), and magnetic force microscopy. Tapping mode AFM is the technique of choice for imaging soft surfaces, cells and biopolymers. For scanning in liquids a special fluid AFM cell can be installed. Additional features of this scanning probe microscope include a semi-automatic probe engagement that minimizes the set-up time, computer controlled motorized sample stage, and a built-in optical microscope to locate objects of interest. Potential users should contact Professor Uwe Happek.

Two large vacuum systems, each with electron gun and energy analyzers, are used for electron scattering experiments. One of the vacuum systems contains an electron gun and two electrostatic energy analyzers. The electron gun is capable of operating in the energy range of 200 eV to 2 keV. The gun and analyzers were designed in our laboratory and constructed by the university instrument shop. The other vacuum system holds an electron gun and three energy analyzers. The electron gun and analyzers were purchased from Comstock, Inc. The gun operates in the range of 200 eV to 5 keV. These systems can be used to study the scattering of electrons by atoms and molecules or to study the ionization and excitation of selected targets. The electrostatic energy analyzers are used to detect scattered electrons, secondary electrons emitted from targets, or fragment ions from the breakup of molecules.

The University of Georgia operates a 24" Cassegrain Reflecting Telescope for student instruction and public nights. The telescope is located in a dome on the roof of the Physics Building and is fully-computer controlled. A 1024 x 1024 Apogee AP6 CCD camera is mounted on the telescope with a pixel size of 24 microns. A full set of UBVRI filters is also available. Once a month during the academic year the telescope is open to the general public. The remainder of the time the telescope is used by the introductory and advanced astronomy classes for general viewing and instruction.

We possess facilities which allow us to synthesize and grow a wide variety of refractive materials in single crystal fiber form using the so-called Laser Heated Pedestal Growth (LHPG) method. Though a number of LHPG stations exist worldwide, our facilities are one of the few solely dedicated to the study and the development of new materials in crystalline form. Pedestal growth, also known as float-zone growth, is a miniaturized variant of the Czochralski method for pulling single crystals; in LHPG, however, the melt is formed on the tip of the feed stock ceramic rod and is held together solely by the surface tension of the melt. Focused laser radiation is used to produce the melt on the feed stock; a seed is dipped into the melt and is wetted by it. As the seed is pulled out, the melt adheres to and forms a pedestal around the seed, enters an unlamented zone and begins cooling and crystallizing into a single crystal fiber. The diameter of the fiber depends on ratio of the pulling and stock feeding rates and can be as small as 10 microns. We have been able to demonstrate that LHPG presents us with a method to grow and synthesize new materials of high quality and purity; the materials grown in this way can be readily characterized physically and optically. Of most importance is the fact that crystalline fibers of macroscopic dimensions can be grown in a matter of minutes providing the necessary feed back for the growth of optimized materials from the point of view efficiency and versatility in their performance.

To date we have been able to grow single crystal fibers of over one hundred materials with a variety of compositions and properties. We have provided crystalline fiber samples of light emitting materials to over twenty other laboratories worldwide. We have been able to grow, for example, single crystal fibers of materials such as yttria which have extremely high melting points and which cannot be normally grown in crystal furnaces. The fiber configuration geometry is also ideal for various optoelectronic applications, such as in-line solid state lasers and other non-linear devices, and for optical spectroscopic purposes. For a detailed description of these developments see: W.M. Yen, �Preparation of Single Crystal Fibers� in Insulating Materials for Optoelectronics, F. Agullo-Lopez, ed. (World Scientific, Singapore, 1998).

BIOPHYSI

CS LASER SPECTROSCOPY LABORATORY

The ultrafast laser spectroscopy laboratory is equipped with a state-of-the-art femtosecond/picosecond laser system. A Ti:Sa oscillator is amplified at kHz rates using chirped pulse regenerative amplification. Broadly tunable (UV-IR) fs/ps pulses are produced via optical parametric amplification (OPA) and subsequent sum frequency / harmonic generation. Additionally, pulses around 400 nm, 266nm, and 200nm are routinely available through sum frequency / harmonic generation of the Ti:Sa fundamental. The laser system is extremely versatile and hence suited for a variety of experiments.

Experimental techniques include pump-probe spectroscopy of biophotonic molecules and molecular clusters in a molecular beam photoelectron photoion coincidence (PEPICO) spectrometer. The photoelectron spectrometer uses a strong, highly divergent magnetic field that meets a weaker guiding field to form a magnetic �bottle� to obtain a high collection efficiency of photoelectrons. Simultaneous ion detection is based on a modified Wiley-McLaren time-of-flight mass spectrometer.

The Department has established a new NanoLab, with a variety of locally designed, state-of-art thin film deposition and nanostructure fabrication facility. A description of the laboratory and its capabilities may be seen here.