Cross Sections DEPARTMENT OF PHYSICS AND ASTRONOMY UNIVERSITY OF ROCHESTER SPRING 2006 Physics and Astronomy • SPRING 2006 Message from the Chair —Arie Bodek Maria Florencia Canelli (Ph.D. ’04) was in physics or astronomy to apply for grad- The Board of Trustees recently chose awarded the American Physical Society’s uate study at Rochester. Application ma- a new president for the University of 2005 Mitsuyoshi Tanaka Dissertation terial for all these programs is available Rochester: J. Seligman. Our own Nick Award in Experimental Particle Physics on our Web pages (www.pas.rochester. Bigelow chaired the for her 2003 Ph.D. dissertation as a edu). If you know of any exceptional faculty committee that University of Rochester student. Young undergraduates whom we should con- conducted this search. Kee Kim (Ph.D. ’90) was awarded the sider either for our REU program or for Several of our faculty, most prestigious Korean Science Prize graduate studies, we would appreciate students, and alumni in 2006 and will assume the post of it if you would please send their names have received awards Deputy Director of Fermi National Ac- and e-mail addresses to Barbara Warren during this past aca- celerator Laboratory in 2006. She has ([email protected]), and we will demic year. I will only also been serving as co-spokesperson contact them directly. Any help from our mention a few and refer you to news of the CDF collaboration at Fermilab. alumni along these lines would be greatly stories on our department Web page for We wish to take this opportunity to welcomed. Several years ago, the Uni- the others. thank all our friends who have contrib- versity initiated a tradition of hosting Professor Joe Eberly has been serving uted so generously to the support of the yearly Meliora Weekend reunions (see as vice president and president elect of department. By completing the form on www.rochester.edu/alumni). I encourage the Optical Society of America and will the last page of our newsletter, you can all our alumni and friends to come and become president in 2007. Assistant Pro- continue (or begin) that tradition of giv- visit us in fall 2006. For the latest news fessor John Howell was awarded the ing that will assure the future excellence about the department, please visit our Presidential Early Career Award for Sci- of the department. Other ways to help Web page, where you can also find the entists and Engineers (PECASE) in 2006. our cause are to inform any promising current and several recent issues of Professors Eric Blackman, Kevin McFar- students about our summer undergrad- Cross Sections online. land, and Lynne Orr were named fellows uate research program (REU) and to en- of the American Physical Society in 2005. courage students interested in careers Cross Sections On the Cover Important notices: Department phone: (585) 275-4344 and fax: (585) 273-3237. Editors: S. Rajeev and R. Demina If you change your mailing address, please Published by the Department of Physics and Chris Haimberger (right) and Jan Kleinert contact Bob Knox with your new whereabouts Astronomy of the University of Rochester, and (left) adjust one of the more than 10 laser ([email protected]). Also let him know distributed to alumni and friends free of charge. systems that they use to control the your current e-mail address. Copies may be obtained by writing to CROSS creation of ultracold heteronuclear SECTIONS, Department of Physics and Astronomy, molecules in Nick Bigelow’s quantum University of Rochester, Rochester, New York optics laboratory. Using these lasers, 14627-0171 USA. sodium and cesium atoms are first cooled to micro-kelvin temperatures. From the To catch up with the happenings at the Univer- sity, log in to www.pas.rochester.edu and find the cold atomic vapor, diatomic heteronuclear latest news. For previous editions of this newsletter, molecules are formed when photons from go to the Alumni and Friends page from the Home a separate laser photoassociates atomic section. Or point your Web browser to http://spider. pairs into bound molecules. The resulting pas.rochester.edu/mainFrame/home/alumni.html. molecules are probed a pulsed dye laser —Webmaster, Steve Teitel and detected by time-of-flight mass spectrometer. The yellow light in the foreground is the ring dye laser used to trap the sodium vapor. In 2005, this Rochester team was one of four groups in the world to create such cold polar molecules using an all-optical approach. 2 SCIENCE HIGHLIGHTS Physics and Astronomy • SPRING 2006 Phase Change in Fluids Finally Simulated after Decades of Effort Everyone knows what happens to a bit like deciding where to go to dinner results, including very precise measure- water when it boils—everyone, that is, —quick and easy with two people, but ments performed in microgravity on the except computers. Modeling the transfor- takes forever for a group of 20 to take Space Shuttle. mation process of matter moving from action. The broadening correlation dra- “In principle, it’s a difficult calcula- one phase to another, such as from liquid matically increases the time it takes for tion,” says Chimowitz. “Fluid systems to gas, has been all but impossible near the gas to reach an overall equilibrium, require a different class of models than the critical point. This is due to the in- and that directly leads to an increase in the common lattice models used by re- creasingly complex way molecules be- computing time required, approaching searchers who have studied dynamic have as they approach the change from infinity and bogging down as the gas critical behavior. These different classes one phase to another. Yonathan Shapir, crosses the point of phase change. give rise to different dynamic critical Eldred Chimowitz, and Subhranil De To illustrate the effect, imagine a per- exponents, and we found them, for the have now created a mathematical model fectly pure and still lake. If you drop a first time, in real fluid systems.” that will allow scientists to simulate and pebble into this lake, its ripples would The best known examples of phase understand phase changes, which could spread outward, dissipating until the changes are perhaps water to ice and have an impact on everything from de- lake had returned to a calm equilibrium water to steam. Phase changes of many caffeinating coffee to improving fuel cell again. But if you were to take this im- different physical types occur, however, efficiency in automobiles of the future. possibly perfect lake just barely above such as the separation of a liquid mix- The findings have been published in the critical point and drop your pebble, ture to its components, which should Physical Review Letters. the ripples would remain as ripples also abide by the Rochester team’s “This problem has baffled scientists much longer—likely bouncing off the results. for decades,” says Yonathan Shapir, pro- distant shores. This imaginary lake The team’s simulation approach will fessor of physics and chemical engineer- would take seemingly forever to return likely be used by industry in a variety ing and coauthor of the paper. “This is to its calm equilibrium again. of ways, not the least of which will be the first time a computer program could The research team of Shapir, Eldred to derive more power from a fuel cell. simulate a phase transition because the Chimowitz, professor in the Department Since fuel cells rely on the transporta- computers would always bog down at of Chemical Engineering, and physics tion of protons through a membrane what’s known as the ‘critical slowdown.’ graduate student Subhranil De created separating two electrodes, Shapir and We figured out a way to perform a kind a novel approach to tackle the phase- Chimowitz believe it should be possible of end-run around that critical point change process. They devised a compu- to use their work to find the most ef- slowdown, and the results allow us to tational model consisting of two separ- ficient configurations for a fuel cell. calculate certain critical point properties ate reservoirs of fluid at equilibrium Other applications, such as removing for the first time.” and near the critical point threshold. the caffeine from coffee, work in a “Critical slowdown” is a phenomenon One reservoir was slightly more pres- similar way and will likely also benefit. that happens as matter moves from one surized than its neighbor. The reservoirs Chimowitz also has just published a phase to another near the critical point. were opened to each other, and the much-praised book about the subject, As molecules in a gas, for instance, are pressure difference caused the fluids to Introduction to Critical Phenomena in cooled, they lose some of their motion mix. The team let the simulation run Fluids from Oxford University Press. but are still moving around and bump- until the entire system reached thermo- The book has been nominated for the ing into each other. As the temperature dynamic equilibrium. By watching the Association of American Publishers’ drops to where the gas will change into rate that equilibrium returned, the team Award for Excellence in Professional a liquid, the molecules’ motion becomes was able to calculate the behavior at and Scholarly Publishing. correlated, or connected, across larger the critical point. Their simulation find- This research was funded by a grant and larger distances. That correlation is ings match predictions and experimental from the National Science Foundation. 3 SCIENCE HIGHLIGHTS Physics and Astronomy • SPRING 2006 Amnon Harel—the New Marshak Fellow Would you take the money or the in- als crucial to selecting which of the 30 teresting job? million events per second should be That’s the question our newest Marshak stored for later physics analysis.