Facilities
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Atomic, Molecular, and Optical Physics
at the University of Delaware addresses theory efforts in molecular physics, intramolecular interactions,
precision measurements, and high intensity physics. Experimental efforts include time resolved ultrafast dynamics,
atoms and molecules in ultrastrong fields, THz radiation, and laser physics. A few highlights are given below from recent research
in the AMO group.
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X. Li, A. V. Volkov, K. Szalewicz and P. Coppens, Acta Cryst. D62, 639-647.
 FIGURE: The electrostatic potential in the antibiotic–substrate region mapped on the 0.02 au electron-density
isosurface in the deglucobalhimycin–DADA complex (a) according to the dataank and (b)
according to the MMFF94 point charge model. The electrostatic potential is color coded as follows:
deep red, -0.04 au; deep blue, +0.50 au; orange, yellow, green and cyan represent intermediate
values as indicated on the color scale. Hydrogen bonds are indicated by dotted lines.
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I Ghebregziabher and B.C. Walker, Phys. Rev. A 77, 023417
FIGURE: Angle- and frequency-resolved total radiation
yield for photoionization of sodium 1s2 in an ultrastrong field of 1.2
1020 W/cm2 for classical versus and coherently
summed tunneling probability current.
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M.F. DeCamp, L.P. DeFlores, K.C. Jones, and A. Tokmakoff, Optics Express 15, 233
FIGURE: Multidimensional infrared spectroscopy is a robust tool
for studying the structural dynamics of molecules. In particular, twodimensional
infrared (2DIR) spectroscopy can reveal vibrational coupling
among the internal modes of molecules, uncovering the transient structure
of complex systems. While spectroscopically very powerful, current
experimental techniques are time consuming to perform, requiring millions of
laser shots for a single 2DIR spectrum.
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U. I. Safronova, W. R. Johnson, M. S. Safronova, Phys. Rev. A 76, 042504
FIGURE: Line strengths in a.u. as functions of Z in Fr-like ions. Relativistic many-body perturbation
theory applied to study properties of ions of the francium isoelectronic
sequence is used to calculate energies of the 7s, 7p, 6d, and 5f states of Fr-like ions with nuclear charges Z;
reduced matrix elements, oscillator strengths, transition rates, and
lifetimes may also be determined.
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UD » Physics & Astronomy » Research » AMO Physics
Atomic, Molecular, and Optical Physics
The goals of atomic, molecular, and optical physics (AMO physics) are
to elucidate the fundamental laws of physics, to understand the structure
of matter and how matter evolves at the atomic and molecular levels, to
understand light in all its manifestations, and to create new techniques
and devices. AMO physics provides theoretical and experimental methods and essential
data to neighboring areas of science such as chemistry, astrophysics,
condensed-matter physics, plasma physics, surface science, biology, and
medicine. It contributes to the national security system and to the
nation's programs in fusion, directed energy, and materials research.
Lasers and advanced technologies such as optical processing and laser
isotope separation have been made possible by discoveries in AMO physics,
and the research underlies new industries such as fiber-optics
communications and laser-assisted manufacturing. These developments are
expected to help the nation to maintain its industrial competitiveness and
its military strength in the years to come. A few of the AMOP research areas at Delaware are highlighted below.
For more contact information, click on the faculty webpages.
Molecular Crystals
We need reliable computational methods to predict properties of condensed phase materials, specifically
molecular crystals and ionic crystals. The first step is a determination of interactions
between molecules, i.e., electronic structure calculations for fixed nuclear positions. One approach is to develop
reliable potentials (force fields) including effects of many-body forces for molecules involved. Another approach is
to perform electronic structure calculations with periodic boundary conditions for molecules of interest placed in a
unit cell. Since often one has to include a large number of molecules in the unit cell, computational requirements
of such calculations can be large. Other important physical effects determining the structure and properties of molecular
crystals are intramolecular degrees of freedom. Most of work in the field assumes rigid molecules. However, partial
deformations of the molecules compared to their gas-phase structures are always present in crystals. In some cases,
torsional deformations can be large.
One needs to know several other properties of materials such as heats of formation, density, etc. Some of them
can be obtained from molecular dynamic calculations for crystals. How reliably can we predict such properties and
at what computational cost? Can the predictions be trusted for notional materials? Finally, are we able to
computationally model chemical reactions in the condensed phase? Can periodic boundary
programs be used for this purpose taking into account that chemical reactions locally break crystal order and therefore
unit cells have to become huge? Other questions that need to be addressed by this research include:
- What systems and properties can be computed and at what costs?
- What is the accuracy and can the methods be developed in the future?
- Can the calculations be validated by experiments?
- Is the theory predictive enough to screen notional materials?
(molecules not synthesized but suspected to have desirable properties)
Terawatt Laser Technology
Ultrafast laser systems can generate laser peak powers exceeding 1012 Watts or a terawatt. In a single laser pulse
the peak power in the photons can exceed the world's average power consumption at any point in time.
Improving the laser technology and our understanding of laser physics is opening up a new area of
science allowing us to see dyanmics at the fastest time scale - the attosecond, or pulse lasers with a duration of 10-18
seconds.
The image shown above is a terawatt laser pulse that has had its energy mode improved by using microlens technology.
Motivation behind exploring lenslet array spatial filtering options
for high-power linear and parametric amplification includes improvements to the focus and peak intensity
of the amplified laser output that affect scientific and industrial applications, increased peak irradiance,
improved spatial contrast at the focus, better pump energy coupling efficiencies, higher reliability and
reproducibility between lasers, control of aberration induced damage, and simplification of design by
elimination of vacuum relay and pinhole spatial filtering. Lenslet arrays may be the companion to recent
technologies allowing control of the spectral amplitude and phase for optical signals and spatial wave-front
phase. The laser pulse shown above has an order-of-magnitude improvement in the spatial contrast
and mode performance. This advance directly affects high-intensity laser science and processing that
require laser pulses with a very high contrast in time and space.
Parity Nonconservation
Study of parity nonconservation in heavy atoms provides atomic-physics tests of the standard model
of the elementary particle physics and led to a first measurement of the nuclear anapole moment.
Our research is aimed at the development of theoretical methods within the framework of relativistic
many-body theory, to treat parity nonconservation (PNC) in heavy atoms. The goal of this research is
to improve the accuracy of PNC amplitudes in atoms and ions of experimental interest.
Reducing the error in PNC calculations leads to more accurate experimental weak charges, a quantity which
depends on input from atomic theory, which in turn provide valuable tests of the standard electroweak
Precise calculations of the nuclear spin-dependent PNC amplitudes provide data needed to extract
accurate anapole moments from PNC experiments. These in turn shed light on inconsistencies
between constraints on weak nucleon-nucleon coupling constants obtained from the experimental anapole
moment of cesium and those obtained from other nuclear PNC measurements. We also work on the
development of high-precision methodologies to conduct calculations of a number of quantities
such as energies, transition rates, hyperfine constants, polarizabilities, and others atomic properties to provide high quality benchmark atomic data for parity conserving quantities which are of interest to other areas of atomic physics as well as astrophysics.
Quantum Computation
Quantum computation is a new field of research that is aimed at using quantum nature of matter to
produce fundamentally new methods of computation and simulation of physical systems. There are
various approaches to the experimental realization of the quantum computation. We are currently
investigating the quantum computation scheme with neutral atoms, where the qubits are realized as
internal states of neutral atoms trapped in optical lattices or microtraps. This approach to quantum
computation has many advantages, such as scalability, possible massive parallelism, long decoherence
times of the internal states of the atoms, flexibility in controlling atomic interactions, and
well-developed experimental techniques. The understanding of the operation of quantum logic gates and
designing a simulator of a quantum gate operation is a vital step toward the road to quantum computation.
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AMO Group
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Krzysztof Szalewicz
Marianna Safronova
John Morgan
Matt Decamp
Barry Walker