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Spring 2002

Schedule Spring 2002

February 22, 2002
3:00 pm (Friday)

Prof. Steven Chu
Stanford University

Laser Cooling and Trapping: From Atomic Clocks to Watching Biomolecules Move, One Molecule at a Time

March 1, 2002
3:00 pm (Friday)

Prof. Robert K Nesbet
IBM Almaden Research Center

A fresh look at density functional theory

In the density functional theory of Kohn and Sham, the occupied orbital functions of a model state are derived by minimizing the ground-state energy functional of Hohenberg and Kohn. It has been assumed for some time that effective potentials in the orbital Kohn-Sham equations are always equivalent to local potential functions. When tested by accurate model calculations, this assumption is found to fail for more than two electrons. Here this failure is traced to the unjustified assumption that functional derivatives of any well-defined density functional necessarily exist in the form of multiplicative local potential functions. A deeper look at the relevant variational theory shows that this is not true. Instead, the fermion nature of interacting electrons implies a more general form of functional derivative, operationally equivalent to a linear operator that acts on orbital wave functions. When extended to include such nonlocal potentials, the theory is free of inconsistencies and paradoxes, formally exact, and explicitly related to standard many-body theory.

March 22, 2002
3:00 pm (Friday)

Prof. Joseph Macek
University of Tennessee and Oak Ridge National Laboratory

Theory of elementary atomic processes in collective systems

Collective systems containing dynamically interacting atomic species are often strongly influenced by elementary atomic processes such as excitation, ionization and electron capture by charged particle impact. Modeling these processes has been a driving for development of atomic theory in the eV to keV energy range. Despite considerable progress exceptional problems remain when there are three or more unbound charged particles. At the other end of the energy scale, in the nano-kelvin range, dilute Bose condensates of atoms are formed. Because the atoms are dilute and the energy is low, they mainly scatter elastically. Three body collisions rarely occur, but they play an important role in setting condensate lifetimes. Some novel features of three-body recombination at the low energies will be described.

April 5, 2002
1:45 pm (Friday)

Prof. Paul Julienne
National Institute for Science and Technology

Quantum Encounters of the Cold Kind

The collisions and interactions of very cold atoms play a prominent role in determining the properties of cold atomic gases. Such interactions are very quantum mechanical in nature, but can be very precisely measured and characterized. It now seems that it will be possible to work with one, two, or three individual atoms tightly localized in optical lattice nanotraps. We will consider how one might study collisions of atoms confined to a volume of only a few nanometers in size.

April 10, 2002
3:00 pm (Wednesday)

Prof. Harold Metcalf
State University of New York, Stonybrook

Dark States and de Broglie Wave Optics

Laser cooling has advanced from a laboratory curiosity to a research tool, and one of the areas for this tool is optical control of atomic motion. It is possible to produce special states of motion that have arbitrarily narrow momentum distributions, and the atoms in these states are blind to the light. With zero detuning, satisfaction of selection rules, and enough intensity to completely saturate the transition, these states remain unperturbed and the atoms stay in their ground states. We say the atoms are in dark states, and it can even happen for two-level atoms. Such fascinating phenomena can lead to new vistas in atom optics, opportunities for extremely "cold" samples, and entanglement that results in a "controlled not" gate.

April 12, 2002
3:00 pm (Friday)

Prof. Colm T Whelan
Old Dominion University

Fragmentation Processes in Atomic Physics

For some years now one of the most exciting areas in Atomic Collision Physics has been that of coincidence studies of ionization. In such an experiment a projectile is fired at a target, ionizes it, and the collisional fragments are detected with their energies and positions in space resolved, i.e. we are talking here about multiply differential cross sections as opposed to those where we have integrated over one or more particle coordinates. Integrated cross sections can be crude things and you need the full power of a highly differential measurement to tease out the delicacies of the interactions. A full coincident measurement gives maximal kinematic information; all that is lacking is a determination of the spins to a have a complete quantum mechanical determination of the scattering process. In this lecture I will consider what we have learned about the Coulomb few body problem in Atomic Physics at both relativistic and non relativistic energies from these studies and I will discuss to what extent we can extract information either explicitly or implicitly about highly correlated atomic states from such scattering experiments.

April 20, 2002
7:30 pm (Saturday)

Dr. Seth Shostak
Senior Astronomer with the SETI (Search for Extraterrestrial Intelligence) Institute

Searching For ET

April 24, 2002
3:00 pm (Wednesday)

Dr. Barry I Schneider
National Science Foundation

Modern Theoretical Methods for Electron-Molecule Collisions

The calculation of accurate electron molecule collision cross sections requires the development of robust theoretical/computational methods which combine modern electronic structure and scattering theory. I will begin with a discussion of the fundamental physical complexities of electron-molecule scattering, and why these cross sections are important for certain applied problems. The bulk of the talk will focus on two of these methods: the R-matrix and Complex-Kohn Variational method. I will discuss the theory and computational details, and compare the two methods. The talk will conclude with a number of illustrations of the methods to the computation of electron scattering from a variety of diatomic and polyatomic molecules.

April 26, 2002
3:00 pm (Friday)

Prof. Dmitry Budker
University of California, Berkeley

Resonant Nonlinear Magneto- and Electro-Optical Effects in Atoms

In this talk, we will review the history, current status, physical mechanisms, experimental methods, and applications of nonlinear magneto- and electro-optical effects in atomic vapors. We begin by describing the pioneering work of Macaluso and Corbino over a century ago on linear magneto-optical effects (where the properties of the medium do not depend on the light power) in the vicinity of atomic resonances, and contrast these effects with various nonlinear magneto-optical phenomena that have been studied both theoretically and experimentally since the late 1960's. In recent years, the field of nonlinear magneto-optics has experienced a revival of interest which has led to a number of developments, including the observation of ultra-narrow (1-Hz) magneto-optical resonances, applications in sensitive magnetometry, nonlinear magneto-optical tomography, and a possible search for parity and time-reversal invariance violation in atoms.

May 24, 2002
10:00 am (Friday)

Dr. Alexander Godunov
Tulane University

Electron Correlation in Atomic Collisions: Dreams and Reality