NEWS OF THE WEEK
DYNAMICS: ‘Light transients’ will enable control of electrons on attosecond scale
A
BEAM OF LIGHT can be split and recombined
into ultrashort pulses with waveforms that have sub-femtosecond features, reports an international team of researchers (Science, DOI: 10.1126/ science.1210268). The work opens up a new way to observe and control electron dynamics. Scientists can also control the structure of the shorter features depending on how the light pulses are combined. That will allow time-dependent study of electron dynamics, says Paul Corkum, head of the Joint Attosecond Science Laboratory of the University of Ottawa, in Ontario, and Canadian National Research Council. He was not involved in the work. To create the pulses, Eleftherios Goulielmakis, a physicist at Germany’s Max Planck Institute for Quantum Optics, and colleagues used a laser to produce a band of light from 330 to 1,100 nm. They then separated the light into three bands of near-infrared, visible, and ultraviolet-visible light. Finally, they brought pulses of the three bands back together at varying times so that the interference of the pulses created distinct waveforms with sub-femtosecond structure. The pulses are also intense, with energies on the order of 0.3 mJ. The researchers call the pulses light transients. The light transients approach can also be combined with standard attosecond spectroscopy, in which a femtosecond laser is used to drive an electron out and then back into an atom to produce a burst of weak X- rays of attosecond duration. Pairing the two techniques enables researchers to examine electron dy-
namics via pump-probe experiments at the attosecond timescale, Goulielmakis says. The group used such a pump-probe method to study ionization of krypton atoms, ionizing them with the light transients and probing them with attosecond Xrays. Goulielmakis and colleagues used the results to quantitatively evaluate the ionization rate and population dynamics of the system. They found that their experimental results agreed with theoretical predictions. “This is very close to a true attosecond-attosecond experiment, and the richness of detail is exquisite,” says Stephen R. Leone, a professor of chemistry and THORSTEN NAESER/MAX PLANCK INSTITUTE FOR QUANTUM OPTICS
LIGHT PULSES GET SHORTER
physics at the University of California, Berkeley, and director of the Chemical Sciences Division at Lawrence Berkeley National Laboratory. Leone collaborated with Goulielmakis and others on predecessor experiments but was not involved in the current work. Goulielmakis and colleagues now plan to use the technique to probe and direct the electron dynamics and chemistry of other systems, from molecules such as glycine to nanostructures.—JYLLIAN KEMSLEY
Goulielmakis and colleagues split a beam of light into three bands, then recombined them to produce ultrashort pulses.
INTERNATIONAL Asian Chemical Congress meeting draws about 2,000 attendees in Bangkok Built around the theme of “Contemporary Chemistry for Sustainability & Economic Sufficiency,” the 14th Asian Chemical Congress was held by the Federation of Asian Chemical Societies (FACS) last week in Bangkok. The congress’ theme reflected the key role of the chemical sciences in addressing global environmental, health, and energy challenges, according to Supawan Tantayanon, chair of the organizing committee and president of FACS. She added that the congress gained special significance because it occurred dur-
ing the International Year of Chemistry. During the congress, FACS admitted the Cambodian Chemical Society to the federation and signed a memorandum of understanding with the American Chemical Society for a three-year collaboration. The Cambodian Chemical Society is just over a year old and has about 100 members, according to Chek Sotha, the society’s president. “We lack instruments, we lack funding,” she told C&EN. By being part of FACS, she added, “we hope to get support,” both material and intellectual.
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The agreement between ACS and FACS “comes from a shared interest in engaging Asian and U.S. chemical communities in collaborations, research, education, and meetings,” ACS President Nancy B. Jackson told C&EN. “We are a global community of scientists who share the responsibility of addressing the critical issues confronting us all: energy, sustainability, clean water, food, and health, and it will take global collaboration to successfully meet these challenges.”— MAUREEN ROUHI
