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Fall 2005

Schedule Fall 2005

September 20, 2005
3:00 pm (Tuesday)

Dr. Michael Coplan
Institute for Physical Science and Technology, University of Maryland

Electron Correlation in Atoms Measured with Double Ionization Experiments

The most direct understanding of electron correlation in atoms is through knowledge of two-electron probability densities. Electron impact double ionization offers the means to directly measure two-electron probability densities provided a number of critical kinematic and mechanism conditions are satisfied. Measurements of double ionization cross sections for the two 3s electrons of magnesium under the required kinematic conditions have led to the identification and separation of the double ionization mechanisms that are the basis of probability density measurements. These results have been supplemented with single ionization measurements and a variety of calculations. A spectrometer based on the results has been designed and will be put into operation.


September 27, 2005
3:00 pm (Tuesday)

Dr. Ted Heilweil
NIST - Gaithersburg

Terahertz Spectroscopy, Imaging and Applications

Terahertz (THz) absorption spectra for substituted benzenes [1] and solid-phase biotin, amino acids, short peptides, [2] sugars and related biomaterials at 4, 77 and 295 K will be presented after a brief methodology overview. A high degree of spectral and structural information exists for these complex systems in the 0.5-20 THz (15 to 666 cm-1) range. The spectral density and uniqueness of distinct features for each system suggests that crystalline, enantiomeric and sequence-dependent structural information can be extracted from THz spectra using quantum mechanical solid-state modeling. Gas phase and solid-state ab initio density functional theory was used to calculate low frequency modes to model neutron and infrared absorption spectra of samples including glycine, L-cysteine, L-serine, tryptophans, glucose, galactose and lactose. Our latest calculations will be compared to experimental spectral results.

We are also investigating methods for extracting transient THz spectral dynamics. Large absorption cross-section differences at excitation wavelengths (UV-VIS) vs. the THz probe (spanning >3 orders of magnitude) makes pump-probe measurements extremely challenging. Systems under study include the trans->cis isomerization of azobenzene and derivatives in solution and as solids.

THz imaging may eventually be a method of choice for materials research, homeland security and medical diagnostics because many substances are transparent in this spectral region. We are attempting to advance multi-channel hyper-spectral methods for imaging large area samples (e.g., semiconductor wafers) to rapidly assess impurity inhomogeneities or imperfections. Examples of sample-scanning and CCD up-conversion methods will be presented and new optical approaches and requirements for wide-area detection discussed.

[1] M. C. Beard, W. T. Lotshaw, T. Korter, E. J. Heilweil, D. McMorrow, J. Phys. Chem. A., 108(43), 9348-9360 (2004).
[2] M. Kutteruf, C. Brown, L. Iwaki, M. Campbell, T. A. Korter and E. J. Heilweil, Chem. Phys. Lett., 375, 337-343 (2003).


October 4, 2005
3:00 pm (Tuesday)

Dr. Matthias Grosse Perdekamp
University of Illinois

The Origin of the Proton Spin: What Can We Learn from Polarized Proton Collisions at RHIC?

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is the first accelerator facility capable of accelerating and colliding polarized proton beams at high energies. This novel experimental technique opens a new window for the investigation of proton spin structure.

The origin of the proton spin has been studied through an enormous, still highly active experimental program extending over 30 years and using a powerful array of accelerator facilities at SLAC, CERN, DESY and Jefferson Laboratory. Despite this very broad experimental effort we are still left with only a rudimentary understanding of proton spin structure.

The colloquium will provide a survey of the experimental opportunities to study proton spin structure at RHIC. We will present first results and discuss the future physics goals of the "RHIC Spin" program.


October 25, 2005
12:30 pm (Tuesday)

Note unusual time

Mr. Robert Friedhoffer
New York University

Einstein and Beyond - The Magic Show

"Einstein and Beyond - The Magic Show" will concentrate on Newtonian mechanics, relativity, and the quantum world. Many of the principles that will be discussed and explained are difficult to see in our everyday existence. Using humor, stagecraft, and lighting, along with laboratory experiments disguised as magical illusion, Friedhoffer will offer a perspective of science that you have never seen before

Bob Friedhoffer brings science information and education to the public using proprietary, unique, innovative forms of exposition that astound, mystify, entertain and edify. In other words, he makes science interesting and fun. For further information on his work you may go to his website, (http://www.sciencetrix.com/) where you can see a list of the books he has authored and toys that he has developed.


October 26, 2005
7:00 pm (Wednesday)

Dr. Robert Friedhoffer
New York University

Einstein and Beyond - The Magic Show

PUBLIC LECTURE

"Einstein and Beyond - The Magic Show" will concentrate on Newtonian mechanics, relativity, and the quantum world. Many of the principles that will be discussed and explained are difficult to see in our everyday existence. Using humor, stagecraft, and lighting, along with laboratory experiments disguised as magical illusion, Friedhoffer will offer a perspective of science that you have never seen before

Bob Friedhoffer brings science information and education to the public using proprietary, unique, innovative forms of exposition that astound, mystify, entertain and edify. In other words, he makes science interesting and fun. For further information on his work you may go to his website, (http://www.sciencetrix.com/) where you can see a list of the books he has authored and toys that he has developed.


November 1, 2005
3:00 pm (Tuesday)

Dr. John A. Tanis
Western Michigan University

Interference Structures In The Ionization Of H2

The ionization of diatomic molecules can give rise to interference effects, in a manner analogous to Young's two-slit experiment, due to coherent electron emission from the identical atomic centers. While such interference was predicted nearly four decades ago, it was only recently that experimental evidence for this effect was observed in fast collisions of ions with H2. The oscillation frequencies of the interference structures depend strongly on the electron observation angle, and, additionally, secondary oscillations with ~2-3 times the frequency of the primary oscillations are observed. This secondary frequency enhancement has been attributed to electron scattering within the molecule, an effect that has no analogy in Young's experiment. Very recent work shows evidence for significantly higher frequency oscillations (by a factor of ~ 20) superimposed on the second-order oscillations, but no explanation for these latter oscillations currently exists.


November 8, 2005
3:00 pm (Tuesday)

Dr. Peter Reynolds
ARO

Circumventing the Fermion Sign Problem by Learning About Wave Function Nodes

The nodal structures of many-body wave functions are largely unexplored. Yet, they are of considerable interest in light of their importance to quantum simulations. The often-used fixed-node approximation simply "assumes" a nodal structure (usually taken from a simple electronic structure calculation). This then bounds the quality of the many-body solution obtainable by most reasonably-convergent Monte Carlo algorithms. Exact nodes, or at least systematically improvable ones, are a way out. Here I discuss what is known about the nodes of a few atoms, and show that there often appear to be unexpected symmetries in the nodal structure. This is of considerable interest in its own right. However, this also points toward an approach towards the goal of a systematically improvable nodal approximation.


November 15, 2005
3:00 pm (Tuesday)

Dr. Swapan Chattopadhyay
Jefferson Lab

Microwave Superconducting Accelerators and Precision Sub-Atomic, Atomic, and Molecular Physics at Jefferson Lab

Following an outline of the scientific canvas of Jefferson Lab, we will describe the enabling technologies and future potential of microwave superconducting accelerators and principle of 'energy recovery' allowing production of bright, intense and femto-second to atto-second pulses of electrons (MeVs to GeVs in energy) and photons (THz, IR, UV and x-rays). Potential 'discovery-class' experiments enabled by these facilities will be discussed.


November 29, 2005
3:00 pm (Tuesday)

Dr. Will Brooks
Jefferson Lab

Quark Propagation, the Strong Force, and the Mystery of QCD Confinement

Of the three fundamental forces, the strong force that governs the interaction of quarks is the most counter-intuitive. Somehow, in even the most violent explosions of strongly interacting systems into individual quarks speeding in all directions, by the time the system cools there are no isolated quarks to be found; only triplets of quarks remain. This "confinement" of quarks, while a unique distinctive of Quantum Chromodynamics, is poorly understood , and remains an important research frontier of modern nuclear physics. In this talk, the basic phenomena will be reviewed, and new experimental avenues for learning more about how energetic quarks evolve into hadrons will be discussed.


December 6, 2005
3:00 pm (Tuesday)

Old Dominion University

Senior Thesis Presentations

"Molecular Models"
Mr. G. C. Greubel

"Stability of Minerals in Organic Artifacts from the USS Monitor"
Ms. Patricia Hoeft

"Orbital Stability of Extrasolar Planets in Binary Star Systems"
Mr. Charles Justin Pearl

"Study of the Corrosion Products on the Turret of the USS Monitor"
Mr. Mark Shaw