November 2005 Archives

The X-ray free-electron laser (XFEL), which will generate extremely brilliant, ultra-short X-ray pulses with laser-like properties, opens up completely new possibilities for the vast field of structural research. Within the framework of the meeting of the XFEL Steering Committee in Berlin, two representatives of the People's Republic of China's Ministry of Science and Technology signed the Memorandum of Understanding for the European X-ray laser project XFEL. Since the beginning of 2005, the ministries of science from 12 countries (Denmark, France, Germany, Great Britain, Greece, Hungary, Italy, Poland, Russia, Spain, Sweden and Switzerland) have already declared their intention to participate in the preparations for the construction and operation of the XFEL. This research facility, which will be unique in Europe, is due to commence operation in 2012. For more information, contact Petra Folkerts, Phone: +49-40-8998-4977, Fax: +49-40-8998-2020, petra.folkerts@desy.de, http://www.xfel.net

Scientists at the U.S. Department of Energy's Argonne National Laboratory have recently unearthed new clues to making magnets longer lasting and more powerful through element-specific X-ray magnetic circular dichroism (XMCD) measurements. They have analyzed magnetic moment reversal at each of two inequivalent Nd sites (g and f sites) in a tetragonal single crystal of Nd₂Fe₁₄B, which is currently known to be the strongest permanent magnet. The results provide clear evidence that intrinsic magnetic stability has its atomic origins predominantly at Nd g sites, which exhibit a strong preference for c-axis alignment at ambient temperature and dictate the macroscopic easy-axis direction. Chemical substitution at Nd f sites, which undermines stability by favoring the xy plane, could enhance intrinsic coercivity. For more information, contact Catherine Foster (+1-630-252-5580, cfoster@anl.gov) at Argonne, and also see the paper, "Atomic Origin of Magnetocrystalline Anisotropy in Nd₂Fe₁₄B", D. Haskel et al., Phys. Rev. Lett., 95, 217207 (2005).

The Japan Society of Applied Physics (JSAP) recently approved the launch of a new professional group for X-ray and neutron analysis on surfaces and 'buried' interfaces. This is significant in that the new group will bring together those who are currently working with X-ray and neutron reflectometry or those who are simply interested in these subjects. So far in Japan, there have been very few meetings to discuss scientific problems in this area despite growing demand. There also exists a strong demand to plan and build beamlines dedicated to reflectometry and related methods at synchrotron radiation (Photon Factory and SPring-8) and neutron facilities (J-PARC to be started in 2008). The group will discuss applications with respect to a variety of materials, i.e., semiconductors, metals, ceramics, polymers, magnetic materials, and multilayers. It is of key importance to extend the technique in order to devise solutions for difficult problems in realistic specimens --. in particular, analysis of specific small areas and/or unstable systems that need to be measured in a very short time. The JSAP has an English-language Web page: http://www.jsap.or.jp/english/index.html

Natural photosynthesis can convert solar energy into chemical energy with almost 100% efficiency. During photosynthesis, O₂ is evolved at a tetra manganese-calcium complex bound to the proteins of photosystem II. As the details of the mechanism have not been fully understood, artificial solar systems still capture only a minute amount of energy. Very recently, a German research group has succeeded in providing new insights into the mechanism by means of time-resolved X-ray absorption spectroscopy, which measures Mn K X-ray fluorescence after laser-flash illumination with a time resolution of 10 μs. The model of the so-called S-cycle treats the manganese complex cycles through five oxidation states, but only four intermediates have been identified experimentally (S0 through S3). Dioxygen is formed during the transition from S3 to S0, but the expected S4 intermediate in this transition has been elusive. Real-time X-ray monitoring of photosynthetic O₂ production has identified the S4 intermediate and, in contrast to previous proposals, the research group concluded that it is formed by a deprotonation process rather than by electron transfer. The experiments were done at beamline ID26, European Synchrotron Radiation Facility (ESRF), Grenoble, France. For more information, see the paper, "Photosynthetic O₂ Formation Tracked by Time-Resolved X-ray Experiments", M. Haumann et al., Science, 310, 1019-1021 (2005).

xfel.net is a new web site, presenting the latest status of the European X-ray laser project XFEL, which is being prepared at DESY, Hamburg. Visit http://www.xfel.net