The Role of Theory in Atomic, Molecular and Optical Physics

(Note this is an archived workshop. For more information on TAMOC's current activities see the TAMOC website.) 9/2012

Organizers: Klaus Bartschat (Drake University), Michael Cavagnero(Univ. Kentucky)

February 26-27, 1999

Sponsored by the Institute for Theoretical Atomic and Molecular Physics at the Harvard-Smithsonian Center for Astrophysics



 ITAMP Workshops

 Schedule of Talks

Friday, February 26, 1999 [Phillips Auditorium]

 8:30 a.m. Coffee: Welcome, Workshop Registration
 8:50 a.m. Introductory remarks:
Kate Kirby - Acting ITAMP Director
Klaus Bartschat - TAMOC Chair

Session IA: A, M and O
Chair: Michael Cavagnero

 9:00 a.m. R. Stephen Berry: Topographies, Patterns and Dynamics on Complex Multidimensional Potentials: Unifying Atomic Clusters and Proteins
9:20 a.m. Pierre Meystre: From Optics to Atom Optics --- A case study of the interplay between theory and experiment and its technological impact
9:40 a.m. Ken Kulander: Interactions of strong, short pulse lasers with atoms and molecules
10:00 a.m. John Delos: Chaotic Dynamics in Quantum Systems: from mathematical games to patented devices
10:20 a.m. Coffee

Session IB: Fundamental Interactions
Chair: Kate Kirby

 10:45 a.m. Walter R. Johnson: Parity Nonconservation in Atoms: Large Role of Atomic Theory in Weak-Interaction Physics
11:05 a.m. Gordon Drake: Theory and Experiment for Lithium and Helium
 11:25 a.m. Anthony Starace: Coherent Control of Atomic and Molecular Processes: An Example of Theory Leading Experiment
 11:45 a.m. Klaus Bartschat: Electron Collisions with Atoms and Ions: How Theory can Guide, Check, Complement, and Extend Experiment
 12:05 p.m. Lunch

Session IIA: Interdisciplinary Studies and Applications
Chair: Gordon Drake

 1:30 p.m. Alex Dalgarno: AMO Physics in Atmospheric Physics and Astrophysics
1:50 p.m. Ken Kulander: Opacities and their role in understanding the universe
 2:10 p.m. David Schultz: AMO Theory and Its Interplay with Applications
 2:30 p.m. Lee Collins: Atoms and Molecules in Environments
 2:50 Refreshments

Session IIB: Theory Centers' Perspectives
Chair: Hossein Sadeghpour

 3:15 p.m. Rick Heller: To be announced
 3:35 p.m. Chris H. Greene:The importance of taking a stand
 3:55 p.m. Joe Eberly: The last part of AMO, namely O

Session III: Roundtable Discussion
4:15 p.m. Moderators: Klaus Bartschat & Michael Cavagnero

 5:30 p.m. Adjourn for Reception - Perkin Lobby
 7:00 p.m. Dinner at Local Restaurant - (TBA)

Saturday, February 27, 1999 [Phillips Auditorium]

Session IV: TAMOC Policy Session
Chair: Joseph Macek

 8:45 a.m. Coffee
 9:00 a.m. Jim McGuire:Survey of AMO Faculty Positions in US Physics Departments
 9:20 a.m. Anthony Starace: Multidisciplinary and Collaborative Work in AMO Theory
 9:40 a.m. Michael Cavagnero: Practical Tasks for TAMOC
 10:00 a.m. Coffee
 10:15 a.m. Discussion of TAMOC Issues
 11:00 a.m. Draft of Report Outline

Topographies, Patterns and Dynamics on Complex Multidimensional Potentials: Unifying Atomic Clusters and Proteins

R. S. Berry
University of Chicago

Understanding how interparticle forces produce multidimensional potential surfaces and, consequently, dynamics and kinetics becomes a considerable challenge for systems of more than about 4 particles. For about 20 or more particles, we cannot expect to be able to use full information about the surface, even if we could generate it. Statistical approaches however open ways to get considerable insight into how systems of 20-20,000 particles behave. One that has been effective takes as its statistical data base sequences of geometrically-linked stationary points, i.e. sequences of the form min-saddle-min..., in which a) the minima form a monotonic series in energy insofar as possible, and b) the database includes crosslinks between sequences. Efficient algorithms are now available for generating such sequences, if a potential is given in analytic or numerical form. Topographies can be classified into sawtooth-like and staircase-like, from such sequences. Sawtooth topographies arise from short-range forces and lead to formation of amorphous structures--"glass-formers". Staircase topographies arise from long-range forces or long-range correlations engendered by constraints such as maintainence of the integrity of a polymer chain, and enable systems to relax to "special" structures such as crystalline geometries or native structures of proteins--"structure-seekers". The statistical databases provide adequate information to construct master equations to describe the kinetics on the surfaces. By coarse-graining and eliminating explicit reference to all but the slowest modes, systems such as proteins lend themselves to simplified modes of exploration of their potential surface topographies, yet retain the basis for constructing master equations. The result is a set of conceptual and computational tools that tie together a range of problems in contexts from clusters to proteins.



From Optics to Atom Optics: A case study of the interplay between theory and experiment
and its technological impact

Pierre Meystre
University of Arizona

I will review the well-known story of how things have happened in optics, with the laser, nonlinear optics, etc., and then move into modern topics such as optical communications and "quantum information processing." I will then draw an analogy with what is happening/will happen in the realm of atom optics, including BEC, nonlinear atom optics, the mixing of matter waves, "atom lasers", lithography, and some ideas on "quantum microfabrication."



Interactions of strong, short pulse lasers with atoms and molecules

Ken Kulander
Lawrence Livermore National Laboratory

Theoretical models of laser-atom (-molecule) interactions have led to several new directions in experimental AMO physics. Highlights include generation of coherent, pulsed 'x-ray' radiation; generation of attosecond pulses; stabilization of atoms and molecules in intense fields; strong-field (strongly non-linear) coherent control and production of very fast ions (including the observation of multiphoton-induced fusion in clusters of D2).



Chaotic Dynamics in Quantum Systems: from mathematical games to patented devices

John Delos
College of William and Mary

When the field of "quantum chaos" got started twenty years ago, it was totally dominated by theorists. Slowly experimenters began to take notice, until today there is a better balance between theory and experiment. In the early days, many of us were excited about how many new things we were learning, but we did not have any practical applications in mind. Now two patents have been filed for new devices which were invented using knowledge gained from the study of chaotic orbits. We will trace how "quantum chaos" moved from theory to experiment to technological applications.



Parity Nonconservation in Atoms: Large Role of Atomic Theory in Weak-Interaction Physics

Walter R. Johnson
Notre Dame University

Experiments during the past 20 years to detect neutral weak currents in atomic transitions are reviewed. The role of atomic theory in extracting weak-interaction coupling constants from PNC measurements is outlined. A status report is given on PNC experiments and on the related theory. Comments are made on future atomic theory needs in this area and on the prospects for progress.



Theory and Experiment for Helium and Lithium

G. W. F. Drake
University of Windsor

Over the past ten years, calculations for the eigenvalue spectrum of helium have advanced to the point that the accuracy of the lowest order nonrelativistic energies and relativistic corrections substantially exceed spectroscopic accuracy for the entire singly-excited spectrum. This has motivated advances in the state-or-the-art for the high precision measurement of atomic transition frequencies in several laboratories around the world. The improved measurements in turn bring new demands for advances in theoretical techniques for the calculation of higher-order relativistic and QED corrections. The exciting interplay between theory and experiment continues to stimulate new developments in both areas. More recently, similar advances in theory have occurred for the more difficult case of lithium. The current status of the field and the outlook for the future will be briefly reviewed.



Coherent Control of Atomic and Molecular Processes An Example of Theory Leading Experiment

Anthony Starace
University of Nebraska-Lincoln

A long-standing goal of theoretical chemical physicists has been to control the rates of molecular processes. Stuart Rice and collaborators at the University of Chicago mapped out theoretically how this might be done using short laser pulses to create and to control the motion of vibrational or electronic wave packets. The key idea is to direct the wave packet in the desired channels using a series of short, coherent laser pulses. Alternatively, Brumer (Toronto) and Shapiro (Weizmann Institute) proposed a "double-slit" type approach to quantum interference involving one- and three-photon pathways toward the same final states, where control can be achieved by varying the relative phase of the third harmonic photon to the fundamental. Both of these approaches to coherent control (i.e., use of short laser pulses or use of "double-slit" type interference) have been taken up by experimentalists (as well as other theorists) not only in chemical physics but also in other areas of AMO physics (e.g., Rydberg wave packet studies). More generally, control of atomic processes by other mechanisms is at present being proposed by theorists well in advance of experimental measurements, e.g., use of external static fields have been proposed to enable control of processes as varied as high harmonic generation and cold atom collisions.



Electron Collisions with Atoms and Ions: How Theory can Guide, Check, Complement, and Extend Experiment

Klaus Bartschat
Drake University

Developments in the formal description and the numerical treatment of electron collisions with atoms and ions over the past 25 years, together with the rapid growth in computer hardware, has opened the opportunity for benchmark comparisons between experimental data and theoretical predictions. For electron scattering from relatively simple (quasi-)one-electron and (quasi-)two-electron targets, the Schroedinger equation can now be solved with high accuracy by using time-independent close-coupling-type methods with a large number of physical and pseudo-states or direct time-dependent lattice approaches. The continuing influence of theory on experiment and the ongoing mutual interaction will be demonstrated with some key examples. These will illustrate how theoretical work has (i) guided experimentalists in what to measure, (ii) helped to assess the accuracy of experimental results, and (iii) provided data of crucial importance for applications. In many cases, these data are nearly impossible to measure in the laboratory, thereby making theory the "only game in town".



AMO Physics in Atmospheric Physics and Astrophysics

Alex Dalgarno
Harvard University

Some examples will be presented where theory led the way in identifying and characterising atomic and molecular processes in atmospheric and astrophysical environments.



Opacities and their role in understanding the universe

Ken Kulander
Lawrence Livermore National Laboratory

Recent calculations of atomic (ionic) transition strengths for iron have very significantly altered the temperature dependent opacities for stars. These classic atomic physics data are fundamental to stellar evolution and in determining the radiative properties of stellar matter. The new results have removed long-standing discrepancies between observations and predictions of theoretical models. The impact involves: estimates of the age and density of the universe, determination of intergalactic distances, big-bang nuclear synthesis, the evolution of the elemental composition of galaxies and in providing constraints on properties of nonbaryonic matter.



AMO Theory and Its Interplay with Applications

David Schultz
Oak Ridge National Laboratory

I will very briefly describe the relationship between AMO theory and some of its significant applications: fusion energy development, astrophysics, and technical plasma processing. The goal will be to elucidate the crucial role for AMO theory in these applications and the feedback and interplay recieved from them.



Atoms and Molecules in Environments

Lee Collins
Los Alamos National Laboratory

Most calculations of atomic and molecular processes focus on isolated systems representative of gas densities, and experiments strive to eliminate environmental effects to yield the closest comparison with theoretical results. While yielding valuable insight into fundamental AMO interactions, these isolated processes also represent, to a good approximation, the mechanisms that govern many low density macroscopic systems, such as plasmas and gases. Therefore, for example, the rates derived from these cross sections have direct application to large-scale kinetic and system modeling. However, for other environments and denser systems, the surroundings begin to affect the basic atomic and molecular processes. Simple models exist to represent these external effects perturbatively and give reasonable corrections for some media. At some stage though, the interactions with the environment require a treatment at a level comparable to the process itself. Such situations arise in a diverse set of media as the atmospheres of giant planets, cool processing plasmas, cage molecules, hollow atoms, liquids, and atomic traps. The above discussion reflects the historical evolution of the treatment of external influences on basic AMO systems. We have reached a stage, theoretically and computationally, beyond perturbation theory, where these environmental effects can routinely be introduced on a par with the treatment of the isolated atomic or molecular process itself. The techniques to handle this regime have arisen from condensed matter physics as well as from the AMO treatment of larger and larger systems, as exemplified by advances in electron-molecule collisions. We shall briefly trace the development of both of these paths and their implications for atomic and molecular systems in environments.



The Importance of Taking a Stand

Chris H. Greene

Progress in theory as a sub-discipline of atomic, molecular, and optical physics is almost impossible to measure. A deeper understanding of natural phenomena, whether from experimental or theoretical studies, hinges on projects that are willing to draw a line in the sand. If there is any one common theme underlying progress in our field, it is this: a new idea has been glimpsed, and then through hard work, turned into a concrete prediction. If we have learned anything from the process, it is that true advances, while rare, would be even rarer if scientists were not willing to make predictions and risk being wrong. My talk will discuss examples where theory has played a positive role in the process, including a case or two where an idea proposed actually turned out to be wrong.



The last part of AMO, namely O

J.H. Eberly

In the 1990's a number of advances have occurred in optical physics, including atom optics, quantum optics, nonlinear optics, and so on. A short list of these, the role of theory, and a vague guess about future directions, might be useful in orienting part of our discussion.



Survey of AMO Faculty Positions in US Physics Departments

Jim McGuire
Tulane University

Data collected from 'Graduate Programs in Physics' published by the American Institute of Physics has been combined with 'Rankings of US Physics Departments' posted on the internet by US News & World Report. All of the top 10 ranked departments have experimental AMO physics. In these 10 departments there are 39.5 AMO experimentalists and 3 theorists. In the top 25 departments, there are 92 experimental AMO physicists in 18 departments. In 9 of these top 25 departments there are listed 12.5 theorists. In the bottom half of the 83 ranked departments, somewhat more than half have either AMO experiment (100.5 positions) or theory (41 positions) with a ratio of theory to experiment slightly exceeding 1/2.5. In the top 10 ranked physics departments, in condensed matter physics there are 59 theorists and 84 experimentalists. Thus, the ratio of theory to experiment is 59:84 = 0.70 in condensed matter; 90:102 = 0.88 in astrophysics; 3:39.5 = 0.08 in AMO physics; 10:40 = 0.25 in nuclear physics; and 84:103 = 0.82 in elementary particle physics.

Graphs and charts will be distributed and discussed.



Multidisciplinary and Multi-Investigator Projects in AMO Physics

Anthony Starace
University of Nebraska, Lincoln

The direction of science is increasingly toward problems requiring multidisciplinary approaches and involving larger groups of investigators. If AMO science is indeed "an enabling science," one might expect more AMO theorists to be involved in such activities than actually are. I will present examples of some successful multidisciplinary and/or multi-investigator projects involving AMO theorists, and then raise questions for group discussion regarding the adequacy of current means to support such activities and whether our professional societies (e.g., DAMOP, DCP, DLS, TAMOC) may play a facilitating role.



Practical Tasks for TAMOC

Michael Cavagnero
University of Kentucky

What can we do together that we cannot do, or are unlikely to do, separately? And why should we bother? Some suggestions from the TAMOC officers and from the community at large will be presented for discussion.