The mandate of C15 broadly covers the properties of charged and neutral atoms and molecules, and the dynamics of these entities, including interactions with electromagnetic radiation.
Commission C15 has traditionally supported two major conferences held in alternate years: the International Conference on Atomic Physics (ICAP), and the International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC). In addition, one or two other topical conferences where appropriate are supported each year. The members of C15 actively promote the role of IUPAP to future conference organizers and encourage the submission of applications for support.
Commission C15 meets every other year in conjunction with the ICAP meeting. In alternate years, business is carried out by e-mail. Over the past three-year period, C15 met in Florence, Italy and in Cambridge, Mass. In addition to discussions of recommendations for conference support, nominees for the new officers and membership of C15 were extensively discussed.
New Developments in the Field
The award of the Nobel Prize for 2002 (the Nobel Centennial year) to Atomic, Molecular and Optical physicists Eric Cornell, Wolfgang Ketterle and Carl Wieman for attaining and studying Bose Einstein condensation in dilute atomic gases. The short delay between the experiments and the prize owes much to the relevance of this advance to the field of Condensed Matter physics and the fact that it is one of the few recent advances which has unified the many subfields of physics.
Recent progress in experimental studies of Bose Einstein Condensates (BEC) includes ways to make BEC’s quickly (few seconds overall) in small traps. These include making it in an optical trap (instead of a magnetic trap) and making the BEC in a small magnetic trap made from wires on the surface of a substrate. The optical trap opens the possibility of forming condensates of non-magnetic atoms or molecules; the surface traps lead naturally to putting BEC’s into single mode atom waveguides on a surface.
Unified theories, applied to cosmology, allow space and time dependence of the coupling constants. Spectroscopy of gas clouds which intersect the sight lines to distant quasars provide stringent constraints on variation of the fine structure constant a. A comparison of such data with new high precision laboratory measurements of optical spectra suggests a smaller a in the past. Laboratory tests are also being undertaken using very accurate frequency standards such as atomic fountains.
The molecular ion H3+ plays a key role in interstellar chemistry and star formation. Many experimental and theoretical studies have been carried out of the rate of destruction of H3+ by electrons (dissociative recombination) but the results are quite contradictory and no theoretical treatment has been in agreement with the best experimental data. However, by identifying a previously neglected decay mechanism, a very recent theoretical calculation has bridged the gap between theory and experiment.
New atomic physics effects have been discovered in astrophysical plasmas in the environment close to hot stars that exhibit extreme brightness. The effects include recombination lines from abundant species (HI, HeI, HeII), two-photon resonance enhanced ionization, atomic radiative cycles involving spontaneous and stimulated emission and laser action with H Lya optical pumping. Modern atomic physics thus enters astrophysics and explains the anomalous brightness of spectral lines in various astrophysical sources.
High precision measurements and calculations continue to play a very important role in atomic physics. Advances in both theory and experiment have been made in spectroscopic studies of two and three electron systems. The development of the so-called Femtosecond Frequency Comb promises to facilitate precision metrology that was formerly possible only at large national standards laboratories. This permits the very precise measurement of frequencies throughout the visible spectrum which is invaluable for the high accuracy study of atomic and molecular transitions.
Correlated many-particle dynamics in Coulombic systems, one of the unsolved problems in physics, can now be experimentally studied using the method of cold target recoil momentum spectroscopy (COLTRIMS). Based on modern cooling techniques and imaging methods a variety of atomic collision processes can be completely explored in momentum space at very high resolution. In recent experiments, durations on the attosecond level of the correlated dynamics between electrons and nuclei have been investigated for atomic and molecular objects. Such “complete” studies have analogies in bubble-chamber experiments in high energy physics.
OUTREACH TO OTHER AMO GROUPS
A discussion has been started about closer contacts between C15 and atomic/molecular/optical divisions such as DAMOP in North America and the Atomic and Molecular Physics Division of the EPS. Extended contacts with Eastern Europe have also been discussed. In this context, Estonia, Latvia and Lithuania were encouraged to apply for membership in IUPAP and they were accepted in 2000 and 2001. Atomic and molecular physics together with laser physics and solid-state physics, belong to the dominant physics activities in these Baltic countries.
Indrek Martinson, Chair
William van Wijngaarden Secretary