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1999

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January, 1999

Seminars

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February, 1999

Seminars

Workshops

Workshop Title

Quantum Information Processing and NMR [Jointly organized by ITAMP and M.I.T.]

Date

February 22-24, 1999

Organizers
David Cory (MIT), Raymond Laflamme (LANL), Ronald Walsworth (CfA), H. Everitt (ARO), E. Knill (LANL)

 
Schedule  Participants

 Title:

"The Role of Theory in Atomic, Molecular, and Optical Physics"

 Date:

February 26-27, 1999

 Organizers:
TAMOC: Klaus Bartschat (Drake University), Chair; Michael Cavagnero (University of Kentucky), Secretary

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March, 1999

Seminars

DAMOP meeting, Atlanta, GA, March 20-26, 1999

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April, 1999

Seminars

Workshop

 Title:

"The Geometric Phase: Recent Developments and Applications in AMO Physics"

 Date:

April 22-24, 1999

 Organizers:
Bernard Zygelman (University of Nevada, Las Vegas and ITAMP); Robert Littlejohn (University of California, Berkeley)

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May, 1999

Seminars

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June, 1999

Seminars

 

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July, 1999

Seminars:

Workshop

 Title:

"Trapping, Spectroscopy, and Collisions of Ultracold Molecules"

 Date:

July 1-3, 1999

 Organizers:
Robert Forrey (Center for Astrophysics); John Doyle (Harvard Physics Department)

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August, 1999

Seminars:

 

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September, 1999

Workshop "Long-Carbon Chain Molecules in Astrophysics" Postponed

Seminars:

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October, 1999

Seminars:

 

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November, 1999

Seminars:

  • November 2, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Prof. Emily A Carter, Dept. of Chemistry and Biochemistry, Univ. of California, Los Angeles: "Ab Initio Molecular Dynamics of Isomerizations: Spectral Signatures Correlated to Molecular Motions"
  • November 3, Wednesday, 4:30 p.m., Jefferson Lab, Room 356 - Joint Atomic Physics Colloquium, Prof. Phillip Gould, University of Connecticut: "Laser-Enhanced Ultracold Collisions"
  • November 9, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Prof Frederick H. Mies, Atomic Physics Division, National Institute of Standards and Technology: "Manipulation of Feshbach resonances in ultracold atomic collisions using time-dependent magnetic fields" [Abstract]
  • November 10, Wednesday, 3:30 p.m., Phillips Auditorium - Quantum Coherence Topical Group Seminars  presents Prof. Eric Heller, Harvard University: "Atomic Scattering Resonances and Superradiance"
  • November 16, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Dr. Verne L. Jacobs, Naval Research Laboratory: "Unified Description of Radiative and Dielectronic Recombination" [Abstract]
  • November 17, Wednesday, 4:30 p.m., Jefferson Lab, Room 356 - Joint Atomic Physics Colloquium, Philip Hemmer: Hanscom Air Force Base: "Raman Dark Resonances for Optical Memory, Aberration Correction, and Quantum Computing"
  • November 23, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Dr. Amichay Vardi, ITAMP: "Adiabatic Population Transfer to the Continuum: Stimulated Raman Photoassociation and Laser Catalysis" [Abstract]
  • November 30, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Dr. Andrei Derevianko, ITAMP: "Role of Negative-Energy States and Breit Interaction in Relativistic Atomic Structure Calculations" [Abstract]

    • Workshop

     Title:

    "Fragmentation and Recombination in Novel 3- and 4-Body Systems"

     Date:

    November 4-6, 1999

     Organizer:
    C.D. Lin (Kansas State University); Brett Esry (ITAMP)

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    December, 1999

    Seminars:

  • December 1, Wednesday, 4:30 p.m., Jefferson Lab, Room 356 - Joint Atomic Physics Colloquium, Dr. Lisa Wiese: University of Wisconsin: "Experimentally Determined Dynamics of the Coulomb-Interacting" Three-Body System H+ + H+ + H-"
  • December 7, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Dr. James R. Anglin, ITAMP, Harvard-Smithsonian Center for Astrophysics: "Black Holes in Bose-Einstein Condensates" [Abstract]
  • December 14, Tuesday, 4:00 p.m., Pratt Conference Room - AMP Seminar, Prof. Uwe Thumm, Department of Physics, Kansas State University: "Do the negative ions of Rb, Cs, or Fr have bound excited states?
    New results on negative--ion resonances in slow electron--atom collisions" [Abstract]
  • December 15, Wednesday, 4:30 p.m., Jefferson Lab, Room 356 - Joint Atomic Physics Colloquium, Prof. Moungi Bawendi, Massachusetts Institute of Technology: "Nanocrystal quantum dots: Uncovering new questions"
  • December 16, Thursday, 11 a.m., Pratt Conference Room - AMP Seminar, Prof. Frederick H. Mies, Atomic Physics Division
    NIST, Gaithersburg: "Intermediate Coupling and Overlapping Lineshapes in Diatomic Predissociation: An Analytic Description Using GMQDT and
    Perturbation Theory" [Abstract]

    •  

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    Abstracts

      Spectroscopy of Highly Charged Ions with an Electron Beam Ion Trap

    Dr. John D. Gillaspy

    National Institute of Standards and Technology

    2.30 PM Monday, June 21, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    Electron Beam Ion Beam Ion Traps (EBITs) can produce, hold at rest, and selectively excite virtually any charge state of any element on the periodic table. A half-dozen or so such EBITs have been constructed around the world during the past decade and used to study ions over a spectral range that is five orders of magnitude wide: from the x-ray down to the visible. Charge states studied have spanned the entire range physically allowed by the
    natural elements: from 1 to 92+ (bare uranium). Most remarkable, perhaps, is that this can be achieved with a device small enough to fit in a closet and cheap enough to be affordable by an individual atomic physics group. This talk will review the capabilities of an EBIT as a spectroscopic light source and present some physics results from work at the NIST EBIT facility (for example, measurement of lifetimes of "forbidden" decay channels and precision tests of two-electron quantum electrodynamics).

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    Cavity Ring Down Spectroscopy on Carbon Chain Radicals 

    Dr. Harold Linnartz

    University of Basel, Switzerland

    4:00 PM Tuesday, June 22, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    Transient molecules, as carbon chain radicals, belong to the chemically most reactive species. This high reactivity complicates spectroscopic studies, as it is hard to generate large
    abundances under laboratory controlled conditions. A very sensitive and generally applicable technique that overcomes this problem is presented here.

    The method is based on cavity ring down spectroscopy in a pulsed slit nozzle, incorporating a discharge in a high pressure supersonic expansion. Cavity ring down spectroscopy
    is immune to pulse-to-pulse fluctuations in the laser power and the generally very long absorption path lengths make this technique ideal to study unstable species. Slit nozzle
    plasmas provide a Doppler free environment and combine high molecular densities and relatively long absorption pathlengths with an effective adiabatical cooling. The combination of both techniques is used here to study electronic transitions of carbon chain radicals that
    might be important as possible carriers of some of the diffuse interstellar bands.

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     "Phase space derivation of propensity rules for energy transfer processes between Born-Oppenheimer surfaces"

    Dr. Bilha Segev
    Department of Chemistry
    Ben-Gurion University, Israel

    4:00 PM Tuesday, July 20, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

                 We consider a simple method based on a phase-space analysis for calculating nonclassical Franck-Condon factors, for understanding non-vertical transitions between different electronic Born-Oppenheimer states, and for studying nonclassical energy-flow patterns within a molecule. The Wigner function of an initial Born-Oppenheimer state is
    calculated for the donor potential surface and projected on the acceptor energy surface. The integrated total projection yields an approximation for the relevant Franck-Condon factors, while local contributions to the overlaps indicate where in phase space the leakage occurs between electronic states of the molecule. This in turn determines initial population and phasing of modes which are initial conditions for subsequent IVR and energy flow. Propensity rules are obtained by recognizing phase-space points of closest approach of the initial-state Wigner function, and the final-state energy surface. The example of two
    coupled harmonic oscillators is explicitly solved to demonstrate the power of this phase-space approach. The methods however is not restricted to the harmonic case.

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    Quantum Localization and Decoherence in
    Time-Driven Nonlinear Systems

    Prof. Hai-Woong Lee
    Department of Physics
    KAIST, Korea

    4:00 PM Tuesday, August 17, 1999
    Pratt Conference Room 

    The phenomena of quantum localization(quantum suppression of classical chaotic diffusion) and decoherence(destruction of quantum coherence) are expected to play a key role in our understanding of the issue of quantum/classical correspondence (or noncorrespondence) in classically chaotic nonlinear systems. In this talk the present theoretical and experimental status of research on these phenomena is described. Discussed in detail is the physical nature of quantum localization. A phase-space approach to decoherence based on the Gaussian-smoothed Wigner function is also briefly described.

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    A Linearized Discrete Ordinate Radiative Transfer Model for Atmospheric Retrieval 

    Dr. Robert. J. D. Spurr

    Harvard-Smithsonian Center for Astrophysics

    4:00 PM Tuesday, October 26, 1999
    Pratt Conference Room

    The forward model simulation of intensities and weighting functions (intensity
    parameter derivatives) is an essential part of the retrieval of atmospheric
    constituent information from measurements of backscattered light. We use the
    discrete ordinate solution of the radiative transfer equation in a plane-parallel
    multilayer atmosphere. We carry out a complete internal first-order perturbation
    analysis of this solution, and we show how this leads in a natural way to the
    generation of analytic expressions for the weighting functions. We examine in
    detail a terrestrial atmosphere application for ozone profile weighting functions
    in the ultra-violet spectral range.

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     Manipulation of Feshbach Resonances in Ultracold Atomic Collisions Using Time-Dependent Magnetic Fields"

    Prof. Frederick H. Mies


    Atomic Physics Division
    National Institute of Standards and Technology

    4:00 PM Tuesday, November 9, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    We have calculated the time-dependent dynamics of two ultra-cold Na atoms in an atom trap where a time-dependent magnetic field $B(t)$ moves a Feshbach resonance state across the energy threshold for a binary collision. Our coupled channels scattering calculations, which
    reproduce the observed properties of such resonances in sodium atom collisions, can be reduced to an effective two-channel configuration interaction model for one bound state and one continuum. The model is adapted to describe the time-dependent dynamics induced
    by $B(t)$ for two atoms trapped either in a strongly-confining single well of an optical lattice or in an optical potential in the presence of a Bose-Einstein condensate. We show that a simple Landau-Zener curve crossing model gives quantitative agreement with exact
    calculations of field-induced transition rates. If $B(t)$ sweeps the resonance across threshold from above, two atoms in the ground state of the trap potential can be efficiently converted to translationally cold dimer molecules. If the resonance is swept from below, the atoms can be removed from the ground state and placed in hot vibrational levels of the trap. Our calculations reproduce the rapid atom loss rates observed in a Na Bose-Einstein condensate due to sweeping a Feshbach resonance state through the binary collision threshold.

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    Unified Description of Radiative and Dielectronic Recombination

    Dr. Verne L. Jacobs


    Naval Research Laboratory

    4:00 PM Tuesday, November 16, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    Radiative and dielectronic recombination of multiply charged many-electron ions in electron-ion beam interactions and high-temperature plasmas are usually treated as independent, non-interfering processes. A projection-operator and resolvent-operator approach has been developed to provide a fundamental, unified quantum-mechanical description of the combined electron-ion photo-recombination process. By means of HULLAC (Hebrew University Lawrence Livermore Atomic Code), dielectronic
    recombination satellite spectra have been obtained for radiative transitions from autoionizing states in Li-like ions. For certain transitions, significant interference effects are predicted in the form of radiatively-modified, asymmetric satellite cross sections or spectral line
    shapes. This ordinary Hilbert-space approach provides a valid description in low-density electron-ion beam interactions or in low-density plasmas.

    A density-matrix formulation has been development for high-density plasmas, for which collisional and radiative relaxation processes can play an important role. Using Liouville-space projection-operator techniques, collisional and radiative relaxation processes are incorporated, on an equal footing and in a self-consistent manner, with autoionization and radiative emission. Both time-independent (resolvent-operator) and time-dependent
    (equation-of-motion) formulations are developed. The density-matrix approach provides a comprehensive description of the broadening of dielectronic satellite spectral lines due to autoionization processes, radiative transitions, electron-ion collisions, and electric and magnetic fields. By means of the density-matrix approach, radiation processes involving resonant and non-resonant transitions in a diverse class of quantized electronic
    systems can be treated within the context of a single quantum statistical formulation.

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    Adiabatic Population Transfer to the Continuum: Stimulated Raman Photoassociation and Laser Catalysis

    Dr. Amichay Vardi


    ITAMP
    Harvard-Smithsonian Center for Astrophysics

    4:00 PM Tuesday, November 23, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    We study adiabatic population transfer processes involving coupling of discrete states to structureless continua. We first consider stimulated Raman photoassociation of two
    atoms by a pair of laser pulses. The process is predicted to be an efficient mechanism for the production of ultracold molecules. Detailed calculations on the radiative association of cold sodium atoms indicate that, per pulse, it is possible for up to 97% of all head-on, cold collisions to end up as internally and translationally cold molecules. This translates to an ensemble efficiency of 6*10^-6 per pulse, at a temperature of 1 microK.

    The formalism is extended to study pulsed laser catalysis. In this scenario, a single strong radiation pulse is used to enhance or suppress tunneling through a potential barrier by inducing transient electronic excitation to a bound state. We simulate pulsed laser catalysis on a one-dimensional Eckart barrier and on a two-dimensional collinear reaction. It is predicted that barrier transmission coefficients could be varied from nearly zero to nearly unity, by tuning the pulse carrier frequency. We note that adiabatic laser catalysis is equivalent in the dressed state picture, to resonant tunneling through a double barrier potential. This explains the point of perfect transmission. Asymmetric, Fano type reactive lineshapes are attributed to interference between the nonradiative tunneling and the optically
    assisted path.

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      "ROLE OF NEGATIVE-ENERGY STATES AND BREIT INTERACTION IN
    RELATIVISTIC ATOMIC STRUCTURE CALCULATIONS"

    Dr. Andrei Derevianko


    ITAMP
    Harvard-Smithsonian Center for Astrophysics

    4:00 PM Tuesday, November 30, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    I will give an introduction to relativistic atomic many-body theory applied to calculations of properties of alkali-metal atoms.

    I will demonstrate that the Breit interaction and negative-energy contributions are comparable to the remainder of Coulomb correlation corrections unaccounted
    for in modern relativistic all-order many-body calculations and hence have to be systematically taken into account.

    In particular, the Breit interaction and negative-energy states contribute 0.6% to parity-nonconserving amplitudes in Cs and 1.1% in Fr. The correction for Cs
    is almost twice the experimental uncertainty and reduces the recently determined [S.C. Bennett and C.E. Wieman, Phys. Rev. Lett. 82, 2484 (1999)] 2.5 sigma deviation in the value of weak charge from the Standard Model prediction to 1.7 sigma.

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     Black Holes in Bose-Einstein Condensates

    Dr. James R. Anglin


    ITAMP
    Harvard-Smithsonian Center for Astrophysics

    4:00 PM Tuesday, December 7, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    As Unruh noted nearly twenty years ago, the exact mathematical analogy between sound waves in non-static hydrodynamics, and massless scalar fields in curved spacetime, allows the creation of event horizons for sound. We propose an experiment to construct such a
    `dumb hole' in a trapped Bose-Einstein condensate. We show that the breakdown of the hydrodynamic approximation at short wavelengths drastically affects the radiative instability of the black hole, replacing the Hawking black body with a `quantum bomb'. This effect
    raises an important issue for post-Einsteinian theories of real black holes, and should be observable in the laboratory.

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     Do the negative ions of Rb, Cs, or Fr have bound excited states? New results on negative--ion resonances in slow
    electron--atom collisions

    Prof. Uwe Thumm


    Department of Physics
    Kansas State University

    4:00 PM Tuesday, December 14, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    We analyze negative--ion resonances in elastic and inelastic total scattering cross sections for slow electron collisions with the heavy alkali atoms Rb, Cs, and Fr. Our calculations are based on the Dirac {\sl R}--matrix method. For incident electrons of up to 2.8~eV kinetic energy, we compare $^3P^o$ and $^3F^o$ shape resonances and $^1P^o_{1}$,$^3P^e$, and $^1D^o_{2}$ Feshbach resonances located below the lowest excitation thresholds of the atomic target in the spectra of the Rb$^{-}$, Cs$^{-}$, and Fr$^{-}$ negative ions with available experimental data and other calculations. We provide resonance parameters, scattering lengths, partial and converged total scattering cross sections, and discuss the relative importance of relativistic effects for the three heavy targets.

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      Intermediate Coupling and Overlapping Lineshapes in Diatomic Predissociation: An Analytic Description Using GMQDT and
    Perturbation Theory"

    Prof. Frederick H. Mies


    Atomic Physics Division
    NIST, Gaithersburg

    11:00 AM Thursday, December 16, 1999
    Pratt Conference Room
    Harvard-Smithsonian Center for Astrophysics

    Abstract:

    An isolated non-degenerate molecular bound state coupled to a single, or a multitude of predissociating continuum states will always exhibit a pure Fano-Beutler lineshape characteristic of a non-overlapping exponentially decaying resonance state. However spin-degenerate electronic states, such as the B Triplet Sigma state of the O2 Schumann-Runge system, are split and coupled by various non-adiabatic effects, and the adjacent levels overlap and couple to common continuum states. We show how the resultant interference and overlapping effects can be treated rigorously using a generalized version of multichannel quantum defect theory (GMQDT) applied to molecular dissociation. Further, we show how applying simple and rather standard perturbation theory to estimate the pertinent quantum defect parameters and then using these in the exact GMQDT expressions, we can obtain excellent agreement with complicated lineshape behaviour which can not be duplicated by the usual superposition of Fano-Beutler lineshapes. We apply the theory to some representive predissociations in O2 and demonstrate the excellent agreement between the exact close-coupled spectra and the simple perturbative expressions.

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