Work in atomic physics includes the studies of interactions of electrons or high-energy photons with matter, in support of experiments performed at Argonne's Advanced Photon Source (APS). Theoretical studies are being conducted on the physics of the photoeffect and Compton scattering by bound electrons, focusing on topics selected in view of basic importance, timeliness, and potential in applications. Comprehensive surveys of photo-interaction data for silicon and graphite are underway. Some of the results are useful for underpinning cross sections and stopping power for charged-particle interactions, namely, basic data for radiation physics.

Ongoing theoretical work in support of a new experiment to measure the neutron electric-dipole moment (EDM) is currently focusing mostly on issues relating to the penetration of neutrons into a perfect silicon crystal in the Bragg reflection process. Preliminary reflectivity measurements at the NIST reactor have been performed and the main instrumental issues appear to have been identified. An experiment to measure the interaction of the neutron's known magnetic dipole moment with the crystalline electric field, intended both to test the principle of the EDM experiment and to calibrate the electric field, is planned for late in 2006.

We also work on representations of complex rational numbers as states of
finite strings of two types of qubits, one for real and one for imaginary
numbers. These rational string states representations have been extended to a
representation of real and complex numbers by defining Cauchy sequences of
the rational string states. The definition of the Cauchy condition, which
mirrored that used in mathematical analysis, is given for sequences of
states of the form | s_{n} >, where s_{n} : {1,...,n} → {0,1}
is a 0 - 1 valued function, and extended to linear superpositions of
sequences of these states.
Much of the work to show that (equivalence classes) of these state sequences
represent real and complex numbers consists in verifying that definitions of
addition and multiplication and their inverses have the requisite properties
and that the set is complete (the set is closed under taking of limits).

Heavy-ion reactions and nuclear structure

Theoretical Physics Research