- Number 338 |
- May 30, 2011
Dima Budker, atom man
Dima Budker, atom man.
What do creating magnetometers that can perform NMR chemical analyses without using any magnets at all, measuring parity violations in atoms of the soft metal ytterbium, and testing the accuracy of the most basic theory underlying the Standard Model have in common?
For one thing, they are but a small sample of the research interests of Dmitry “Dima” Budker, a member of the Nuclear Science Division at DOE’s Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley. The pursuits of Budker and his group range far afield, from searching for variations in the fundamental constants of nature to testing the optical properties of superfluids to seeking out biomagnetism in plants – specifically in a plant known, for its size and smell, as the “giant corpse flower.”
True, all these investigations can be gathered under the umbrella of atomic physics, and indeed Budker won the American Physical Society’s award for Outstanding Doctoral Thesis Research in Atomic, Molecular, and Optical Physics (AMO) for the thesis underpinning his 1993 Ph.D. from UC Berkeley. Since then he has extended the theories and techniques of AMO into surprising nooks and crannies.
Born in the former USSR, Budker’s parents were a prominent physicist and a well-known TV journalist and science reporter. He attended the Novosibirsk State University and in 1985 received his Diploma (MS) with honors. Before moving to the U.S. in 1989 he served as a junior researcher at the Institute of Nuclear Physics, where he conducted research on laser spectroscopy of atoms.
On the one hand, Budker is fascinated by atomic physics as a testbed of such fundamental constants and symmetries of nature as the fine-structure constant, time reversal, and parity. In 2009 Budker and his colleagues designed an apparatus that sent a beam of ytterbium atoms flying through orthogonal electric and magnetic fields, where the flow of weak-force currents within the ytterbium atoms enabled “forbidden” transitions when they were excited by a pump laser. With this set-up the experimenters recorded the largest parity violations ever measured in an atom.
“At a small level, the measured atomic parity violation effect depends on how the neutrons are distributed within the nucleus, specifically their mean square radius,” Budker says. “The mean square radius of the protons is well known, but this will be the first evidence of its kind for neutron distribution.”
Drilling deeper into the underpinnings of modern physical understanding, in 2010 Budker and his colleagues made exquisitely sensitive tests of the spin-statistics theorem, one of the major theoretical assumptions of quantum field theory. In essence they asked whether photons are really perfect bosons.
The experimenters illuminated a beam of barium atoms with two laser beams, then repeatedly tuned their wavelengths through the region where forbidden two-photon transitions, if any, would occur. This time the forbidden transitions successfully remained hidden, limiting the probability that two photons could be in a fermionic state to at best one in a hundred billion.
“We keep looking, because experimental tests at ever-increasing sensitivity are motivated by the fundamental importance of quantum statistics,” Budker says. “This was a true tabletop experiment, able to make significant discoveries in particle physics without spending billions of dollars.”
As for practical applications of atomic spectroscopy, the list of Budker group experiments is long indeed. One uses sensitive magnetometers to measure the magnetism of the human heart. Another uses lasers such as those in astronomical observatories to excite naturally occurring sodium gas in the middle atmosphere: by employing sodium’s optical properties as a magnetometer, variations in Earth’s magnetic field can be mapped for navigation, atmospheric science, and Earth sciences far more economically than at present.
Most recently, Budker and his group, collaborating with their longtime colleagues in the group of Alex Pines, of Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Department of Chemistry, have demonstrated that it’s possible to obtain detailed NMR spectra of chemical compounds without using any magnets at all. Instead of measuring chemical shifts – the mainstay of NMR but only apparent in strong magnetic fields – their zero-field technique uses an optical atomic magnetometer to measure J-coupling, the inherent magnetic interactions between nuclei with quantum spin.
The device needed to perform these sensitive measurements is no bigger than a football and already shrinking fast. Says Budker, “We’re just beginning to develop zero-field NMR, but we’ve already shown that we can get clear, highly specific spectra, with a device that has ready potential for doing low-cost, portable chemical analysis.”Budker, the recipient of a National Science Foundation CAREER Award, a Miller Research Professorship at UC Berkeley, a National Institute of Standards and Technology Precision Measurement grant, an R&D 100 Award for laser-detected magnetic-resonance imaging, and chosen as an American Physical Society Outstanding Referee, is a Fellow of the American Physical Society. His explorations of the universe using laser spectroscopy of atoms and other ingenious techniques, although they’ve barely begun, have already opened new applications and new vistas for research.
Submitted by DOE's Lawrence Berkeley National Laboratory