Departmental Groups
Related Research Groups
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Atomic Physics
The program in atomic physics involves work with simple atomic and molecular
systems in the gas phase, at surfaces, and in solids. The inherent precision
of measurements on simple atomic and molecular systems is used in studies
of fundamental physics as well as for certain applications. Experimental
work frequently involves the use of Nd:YAG lasers, dye lasers, diode
lasers, Ti:sapphire lasers, argon and krypton ion lasers, optical, ultraviolet
and infrared spectrometers, microwave and radiofrequency spectrometers,
signal processing equipment, and computers and their interfacing to
apparatus. Students often need a detailed theoretical understanding
of certain aspects of quantum mechanics, group theory, electricity and
magnetism, nuclear physics, surface physics, physical chemistry, fluid
dynamics, and plasma physics to complete their dissertation work.
An important area of active research is the study of spin interactions of
atoms and nuclei. Princeton has historically been, and continues to be, a
world center for such activities. For instance, optical pumping is used to
produce high polarizations in vapors of alkali-metal atoms.
Through
spin-exchange collisions, the polarization of the alkali-metal atoms can be
transferred to a variety of noble-gas nuclei.
The use of "optical pumping
spin-exchange" makes it possible to polarize the nuclei of large quantities
of gases such as He-3 and Xe-129 for a variety of applications. One such
application is a new technique for doing magnetic resonance imaging (MRI).
Polarized noble gases are introduced into the lungs of an animal and
subsequently imaged using fairly standard MRI techniques. The use of
laser-polarized noble gases results in enormous increases in signal strength,
thus opening many new possibilities for medical imaging. Another application
is the production of polarized nuclear targets for accelerator-based
experiments. Many of the innovations that make laser-polarized gas targets
a practical possibility were developed at Princeton.
On the more fundamental side, the spin interactions of atoms offer a huge
and rich area for study. The interaction of polarized light with atoms,
of polarized atoms with each other, and of polarized atoms with surfaces,
are all active areas of research. Important questions include identifying
the mechanisms that cause spin relaxation, as well as the means by which
polarization can flow from one system to another. Research topics include
the spin interactions of atoms that are in the solid state, such as xenon
ice and alkali-metal hydrides. In much of this work, laser techniques are
used in combination with nuclear magnetic resonance to produce powerful new
experimental probes.
Spin-polarized atoms are also used to address fundamental questions in
particle physics. Precision measurements of interactions between
spin-polarized atoms and external fields can reveal the
properties of elementary particle interactions. Time reversal symmetry, CP and
CPT symmetry, and Lorentz invariance are being tested in such
experiments. For
example, measurements of the precession frequency of Xe-129 spins
in a strong electric field determine the electric dipole moment of Xe-129, which
is sensitive to CP violation beyond the Standard Model needed to
explain the asymmetry between matter and anti-matter in the Universe.
Atomic Physics Research Group Homepage
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William Happer:
Spin-polarized atoms and nuclei, optical pumping, magnetic resonance imaging, hyperfine interactions, surface interactions. |
Michael Romalis:
Precision measurements, symmetry tests, magnetometers,
spin-polarized atoms. |
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| Yuan-Yu Jau: Optical pumping, spontaneous generations of quantum coherences, atomic chronometry and magnetometry, spin-polarized systems, numerical modeling of atomic systems |
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