September 2007 Archives

Generally, the structure, composition, and dynamics of the Earth's lower mantle are influenced by the electronic state of iron within minerals at high pressure and temperature. For instance, if this electronic state leads to a change in the density of minerals, it would alter the travelling velocity of sound waves. Dr. Jung-Fu Lin (Lawrence Livermore National Laboratory, California, USA) and his colleagues recently determined the spin state of iron in ferropericlase [(Mg_0.75,Fe_0.25)O] at lower-mantle pressures and temperatures using an X-ray emission spectrometer with in-situ synchrotron X-ray diffraction in a laser-heated diamond cell. They found that the transition between high and low spin happens at temperatures ranging from 1,900 to 2,300 K and pressures of up to 95 GPa: conditions found between 1,000 and 2,200 km below the surface. Through integrated absolute difference (IAD) analysis of FeKb spectra, they obtained the ratio of the high-spin to low-spin states in the sample. An energy shift of 1.6 eV in the main emission peak was interpreted as evidence of the spin transition. X-ray spectroscopists might find further significant spectral changes, e.g., Kb' satellite, in their data. For more information, see the paper, "Spin Transition Zone in Earth's Lower Mantle", Jung-Fu Lin et al., Science, 317, 1740-1743 (2007).

The recipient of the 2nd Asada Award, which is presented in memory of the late Professor Ei-ichi Asada (1924-2005) to promising young scientists in X-ray analysis fields in Japan, is: Dr. Hiromi Eba (one of previous members of our lab, present affiliation, Musashi Tech. Institute, "Site occupancy determination and magnetic evaluation of MnZn-ferrites using MnKb X-ray fluorescence spectra"). The ceremony was held in Kyoto, during the international conference on X-ray optics and microscopy (ICXOM 2007) and the 43rd Annual Conference on X-Ray Chemical Analysis, Japan.

Since 2005, the APEC "Technological Cooperative Framework of Nano Scale Measurement and Analytical Methods" has been aiming to share the most recent advances in nanometer analytical and measurement methods from representatives of government, the private sector, R&D organizations and academia. To this end, the 2007 APEC nanoscale measurement forum was organized by Industrial Technology Research Institute (ITRI), Taiwan, and was held at Taipei, on September 5-7, 2007. The invited speakers were as follows; Peter Hatto (IonBond Ltd., Chairman of ISO/TC 229), Chanchana Thanachayanont (National Metal and Materials Technology Center, Thailand), Wen-Li Wu (NIST, USA), Michael Garner (Intel, USA), Chih-Ming Ke (Taiwan Semiconductor Manufacturing Company), Aleksandar Stefanovic (PANalytical, Singapore), Sang-Hee Suh (Center for Nanostructured Materials Technology, Korea), Kenji Sakurai (NIMS, Japan), Laura E. Depero (University of Brescia, Italy), Chun Zhang (Nano and Advanced Materials Institute, Hong Kong), Keiji Takahata (AIST, Japan), and Keh-Chyang Leou (National Tsing Hua University, Taiwan). For further information, contact Wei-En Fu, Center for Measurement Standards, ITRI, Taiwan, Phone +886-3-573 2220, WeienFu@itri.org.tw, http://www.nml.org.tw/en/APECNanoForum/

X-rays have been used as a tool for probing atomic-scale structures. Used in combination with pump by laser (usually from the infra red to visible light region), time-resolved X-ray (or soft X-ray) analysis is pushing back the frontiers in the world of materials. Recently, a further way of performing pump-probe experiments, i.e., an X-ray pump and infra-red probe, has been successfully applied to clarify the dynamics of N₂ molecules. A research team led by Professors H. Kapteyn and M. Murnane (University of Colorado, Boulder, USA) employed 43 eV soft X-rays with ca. 5 fs pulse width, which are laser-generated high-order harmonics, and an intense IR laser pulse (1.5 eV, 30 fs, 10¹³ W/cm²). The team found that substantial fragmentation occurs through an electron-shakeup process, in which a second electron is simultaneously excited during the soft X-ray photoionization process. During fragmentation, the molecular potential seen by the electron changes rapidly from nearly spherically symmetric to a two-center molecular potential. For more information, see the paper, " Soft X-ray-Driven Femtosecond Molecular Dynamics", E. Gagnon et al., Science, 317, 1374-1378 (2007).