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SSRL Headlines Vol. 11, No. 2  August, 2010


Contents of this Issue:

  1. Prof. Chi-Chang Kao Named Associate Laboratory Director for SSRL
  2. Science Highlight — Unusual Structure Found for an Organic Semiconductor
  3. Science Highlight — Topological Insulators Take Two Steps Forward
  4. New Solar Energy Conversion Process Discovered by Stanford/SLAC Engineers Could Revamp Solar Power Production
  5. SSRL Thanks Piero Pianetta, Welcomes Chi-Chang Kao
  6. Energy Secretary Dedicates World's Most Powerful X-ray Laser
  7. Jeffrey Lee to Receive Spicer Young Investigator Award
  8. Annual SSRL/LCLS Users' Conference - Oct 17-21, 2010
  9. User Administration Update
  10. SSRL Summer School Shines a Light on Sulfur

1.   Prof. Chi-Chang Kao Named Associate Laboratory Director for SSRL
       SLAC Today article by Kelen Tuttle

Chi-Chang Kao
Chi-Chang Kao
A warm welcome to SLAC's newest Associate Laboratory Director, Chi-Chang Kao, who arrived for his first official day of work at the laboratory on August 23. As Director of the Stanford Synchrotron Radiation Lightsource, Kao will manage the day-to-day operations of the SSRL user facility and program, and provide the leadership and vision for the future of the SSRL science and user program. Kao will also have an appointment on SLAC's faculty as Professor of Photon Science.

"We've not only recruited an outstanding individual in management and leadership, but also a person who really excels in x-ray science and techniques," said Keith Hodgson, Associate Laboratory Director for Photon Science. "[In his previous post] as Chairperson of Brookhaven National Laboratory's National Synchrotron Light Source, Chi-Chang demonstrated that he can undertake his new role very effectively. He's also an extremely accomplished physicist in the area of x-ray physics and scattering. Both of these elements-strong leadership skills and scientific research expertise will serve him well at SLAC." Read more at:

2.  Science Highlight — Unusual Structure Found for an Organic Semiconductor
       (contacts: J. Rivnay,; M.F. Toney,

Schematic of face-on molecular packing of P(NDI2OD-T2) inferred from x-ray data (top). Proposed microstructural arrangement of the crystallites (bottom).
Discovering high performing organic semiconductors is a hot area of research, as we look for efficient, low-cost materials that can be used in inexpensive electronic devices, such as flexible solar cells and radio frequency ID tags. To design effective materials, the relationship between a material's structure and its semiconductive properties must be found. Research on p-type (hole conducting) organic semiconductors has shown pi-bond stacking to be important in determining the semiconducting properties. The newer, n-type (electron conducting) class of organic semiconductors has not been as extensively studied.

A group of scientists at Stanford University, including graduate student Jonathan Rivnay and Prof. Alberto Salleo, working with SSRL staff scientist Mike Toney and Antonio Facchetti from Polyera Corp., investigated the structure and properties of an n-type semiconducting polymer thin film using SSRL Beam Lines 11-3, 7-2, and 2-1. They found that the polymer molecules, previously thought to be disordered, packed in a face-on manner with the pi-bonds mostly perpendicular to the film, unlike the p-type semiconducting materials.

This structure is unexpected, since a molecular arrangement with the pi-stacking along the film surface (usually found in p-type polymers) was thought to be critical for conducting charges. The researchers hypothesize that extensive interconnectivity in the polymer structure allows multiple pathways for electrons to travel through the material. These results highlight the importance of understanding how structure influences function in semiconducting organics. This work was published on the Advanced Materials website on July 9, 2010.

To learn more about this research see the full scientific highlight

3.  Science Highlight — Topological Insulators Take Two Steps Forward
       SLAC Today Article by Lori Ann White

Bi2Se3 image
(a) Illustration of the massless Dirac fermion state in undoped Bi2Se3 topological insulator, with the Dirac point connects the upper and lower Dirac cones. (b) A gap at the Dirac point caused by magnetic doping breaks the continuity of the Dirac cones, making the Dirac fermion massive. (c) Measured electronic band structure of a magnetically doped Bi2Se3 sample shows the Dirac gap that separates the upper and lower Dirac cones.
A team of researchers from the Stanford Institute of Materials and Energy Science, a joint institute of the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, and their international collaborators have pushed research into topological insulators not just one, but two steps forward.

Taken together, both steps bring the unique material closer to use in the nascent technology of spintronics, with the potential to result in, among other advances, smaller, more efficient transistors and memory devices. Both steps could also give physicists from fields as varied as condensed matter physics, cosmology, and particle physics glimpses into such exotic phenomena as magnetic monopoles, the fractional quantum Hall effect and axion fields, for starters.

As explained in a paper in Science, in step 1, Chen and his collaborators took the marvelous property of a three-dimensional topological insulator-in which electrons flow inexorably along the surface in the same direction, slaloming around defects instead of scattering off them in all directions-and broke it.

In step 2, the team demonstrated the ability to "tune" the topological insulator's Fermi energy level, the amount of energy in the most energetic electrons still occupying a specific quantum state.

Essentially, the team completely redrew the energy portrait for the topological insulator. Initially the portrait showed two cones, called Dirac cones, with their apexes touching at the so-called Dirac point, where electrons can cruise serenely along the insulator's surface. Introducing magnetic impurities into the system turns electrons into bumbling pedestrians that scatter and bounce off the impurities, in effect creating a gap separating the upper and lower Dirac cones. While tuned into that gap, the usually free flow of electrons across the material's surface remains "broken." Read more at:

To learn more about this research see the full scientific highlight

4.   New Solar Energy Conversion Process Discovered by Stanford/SLAC Engineers Could Revamp Solar Power Production
       Stanford Report Article by Louis Bergeron; additional reporting by Lori Ann White for the SLAC Today

Nick Melosh, assistant professor of materials science and engineering, stands beside the ultra-high vacuum chamber used in the tests that proved the PETE process works. (Photo by L.A. Cicero)
SLAC and Stanford researchers have figured out how to simultaneously use the light and heat of the sun to generate electricity in a way that could make solar power production more than twice as efficient as existing methods and potentially cheap enough to compete with oil.

Unlike photovoltaic technology currently used in solar panels-which becomes less efficient as the temperature rises-the new process excels at higher temperatures.

Called "photon enhanced thermionic emission," or PETE, the process promises to surpass the efficiency of existing photovoltaic and thermal conversion technologies.

"This is really a conceptual breakthrough, a new energy conversion process, not just a new material or a slightly different tweak," said Nick Melosh of the Stanford Institute for Materials and Energy Science, a joint institute of the Department of Energy's SLAC National Accelerator Laboratory and Stanford University. Melosh led the research group. "It is actually something fundamentally different about how you can harvest energy." And the materials needed to build a device to make the process work are cheap and easily available, meaning the power that comes from it will be affordable. Melosh is senior author of a paper describing the tests the researchers conducted. It was published August 1 in Nature Materials.

"Just demonstrating that the process worked was a big deal," Melosh said. "And we showed this physical mechanism does exist, it works as advertised." Critical to the team's efforts to demonstrate PETE was time spent at the Stanford Synchrotron Radiation Lightsource, said Jared Schwede, lead author of the paper and a graduate student working with Melosh. "It's that experimental infrastructure at SLAC that made some of our experiments possible," Schwede said, along with his colleagues' expertise. Read more at:

See also:

5.   SSRL Thanks Piero Pianetta, Welcomes Chi-Chang Kao
       SLAC Today article by Kelen Tuttle

Piero Pianetta
Piero Pianetta (Photo by B. Plummer)
Late last week, nearly 100 people gathered on the Stanford Guest House patio to thank Piero Pianetta for serving as SSRL's Acting Director for the past year, and to welcome new SSRL Director Chi-Chang Kao.

"It has been one of the greatest pleasures of my job to get to know Piero over the last year," said SLAC Director Persis Drell. "He's been a great leader for SSRL, and is a very respected voice in the laboratory community. Piero has managed major transitions at SSRL and has really been leading the light source to the future."

Drell continued: "We are also here to celebrate and welcome Chi-Chang as our new Associate Laboratory Director for SSRL. In my first conversation with Chi-Chang [two years ago], I had a very strong feeling that this guy belongs at SLAC. He brings a breadth of vision and experience. He's a strong voice for SSRL and future of photon science more broadly. I am confident that Chi-Chang will lead us and SSRL to the future." Read more at:

6.   Energy Secretary Dedicates World's Most Powerful X-ray Laser
       SLAC National Accelerator Center News Release

LCLS Dedication
Secretary Chu presents John Galayda with a plaque for his work as director of LCLS construction. (Photo by B. Long)
Secretary of Energy Steven Chu on Monday dedicated the Linac Coherent Light Source, the world's first and most powerful x-ray laser, at the Department of Energy's SLAC National Accelerator Laboratory.

"The LCLS shows what the scientific workforce of our nation, in cooperation with our international partners, is capable of achieving," said Secretary Chu. "Pioneering research will remain critical if the U.S. is to stay a global leader when it comes to innovation and competitiveness."

Stanford University President John Hennessy spoke alongside Secretary Chu and other guests, including U.S. representatives Zoe Lofgren (D-San Jose) and Mike Honda (D-San Jose). "I'm struck by the many accomplishments of SLAC and the many ways the researchers here exemplify the pioneering tradition for which Stanford is known," Hennessy said. "For almost half a century, SLAC has been adventurous in its thinking, boldly launching new efforts in its search for knowledge. We're privileged to have this world-class research facility here at our university."

SLAC Director Persis Drell said, "We at SLAC could not have delivered the LCLS on our own; the Department of Energy, Stanford University and all our partners were always there when we needed them. And now we have a facility that is annihilating expectations. The early experiments are swimming in data and are already exploring new frontiers-the science is starting to flow."

Read more at:

See also:

7.   Jeffrey Lee to Receive Spicer Young Investigator Award
       SLAC Today article by Kelen Tuttle

Jeffrey Lee
Jeffrey Lee at Bandelier National Monument. (Photo courtesy of J. Lee)
Jeffrey Lee, Assistant Professor in the Department of Laboratory Medicine and Pathobiology at the University of Toronto, has been named the 2010 recipient of the William and Diane Spicer Young Investigator Award. The award, created in honor of William Spicer, co-founder of SSRL and a pioneer in photoemission spectroscopy, and his wife, Diane, pays tribute to a young researcher whose work has benefitted from or is beneficial to the Stanford Synchrotron Radiation Lightsource or the worldwide synchrotron community.

"I'm very happy," said Lee. "It feels very nice to be recognized for my work."

The award, which is open to senior graduate students and those seven or fewer years into their professional scientific careers, will be presented on October 18 at the SSRL/Linac Coherent Light Source Users' Meeting. In turn, Lee will give a short presentation describing his recent research.

Until last month, Lee worked as a postdoc in the laboratory of Erica Ollmann Saphire at the Scripps Research Institute. There, he studied the Ebolavirus, which causes an untreatable disease that kills 50 to 90 percent of people who contract it. Using SSRL and other U.S. synchrotrons, Lee was able to uncover the structure of the Ebolavirus glycoprotein, which initiates the attachment and fusion of the virus and the host membranes, when it was bound to an antibody from a human survivor of the virus.

The work was especially challenging because glycoproteins are very difficult to crystallize. As a result, Lee and his colleagues needed to make over 140 different protein variants and grow over 50,000 crystals before finding one that would diffract the synchrotron light well enough to create images. But once they did, they were able to reveal the protein's structure, offering insight into why antibodies for the virus are so rare and into the very few sites to which an antibody can bind. This provides templates for the future development of immunotherapeutics and vaccines that may work against the virus. (More about this research can be found in the SSRL Highlight linked below.) Read more at:

8.   Annual SSRL/LCLS Users' Conference - Oct 17-21, 2010
       (contact: C. Knotts,

Plan to participate in the Annual SSRL/LCLS Users' Meeting and Workshops, October 17-21, 2010 to learn about the latest plans, new developments and exciting user research at LCLS and SSRL. It is also a great time to interact with other scientists, potential colleagues, and vendors of light source-related products and services.

The event kicks off on October 17 with workshops focused on LCLS Data Analysis and LCLS II. LCLS/SSRL 2010 officially begins on October 18 with a joint plenary session featuring updates from SLAC and DOE, a keynote talk by Jens Norskov on "Converting Sunlight into Fuels - the Role of Interface Catalysis," science highlights from SSRL and LCLS, and a user science poster session. The Spicer Young Investigator Award, Klein Professional Development Award, Lytle Award, and the Outstanding Student Poster Session Awards will be presented on this day.

Separate sessions focusing on SSRL and LCLS facility development, instrumentation, and user science will be held concurrently on October 19, followed by meetings of the respective SSRL and LCLS Users' Organizations.

A number of concurrent workshops will be held on Wednesday, October 20, including Frontier Biology and Imaging with XFEL; Challenges in Imaging Processing in Tomographic Data Sets; High Energy Density Science; AMO Instrumentation and Science Opportunities; SXR Instrumentation and Science Opportunities; and Developing Strategies, Preparing and Getting the Most from Macromolecular Crystallography Experiments.

9.   User Administration Update
       (contact: C. Knotts,

SSRL BEAM TIME REQUEST DEADLINES. Proposal spokespersons or their authorized lead contacts can submit new beam time requests for the first scheduling period in our 2011 experimental run (mid November 2010 - February 2011) by September 1. Requests for time on Macromolecular Crystallography (PX) time are due September 15. Request beam time via the user portal.

SUBMIT NEW SSRL PROPOSALS BY SEPTEMBER 1 (X-ray/VUV) OR DECEMBER 1 (PX/X-ray/VUV). New proposals can be submitted 3 times a year: June 1, September 1, and December 1 for X-ray/VUV and April 1, July 1, and December 1 for Macromolecular Crystallography (PX). X-ray/VUV proposals submitted by September 1 will be peer reviewed, rated and eligible for beam time beginning in February 2011. Both X-ray/VUV and PX proposals should be submitted via the user portal.

See our 2011 Operating Schedule.

10.   SSRL Summer School Shines a Light on Sulfur
       Excerpted from SLAC Today article by Kelen Tuttle

Hands-On Session
Summer school participants prepare samples for low-energy S K-edge XAS. (Photo courtesy of R. Sarangi)
Nineteen graduate students, postdocs and researchers gathered at SLAC in late July for the SSRL Structural Molecular Biology Low-Z XAS Summer School.

The workshop focused on a technique called low-energy x-ray absorption spectroscopy. When conducting XAS, a researcher aims an x-ray beam at a sample and tunes the beam through a range of energies. Specific chemical elements absorb specific energies, so when just the right energy beam hits the sample, atoms of a particular element will eject electrons, providing information about the atom's electronic structure. In particular, the workshop covered low-energy ranges (from 2.4 to 4 keV) and the element sulfur, a technique called "S K-XAS."

With applications in biology, chemistry, and environmental and materials science, S K-XAS and x-ray fluorescence imaging can be used to probe metal-sulfur bonds that make certain human proteins function, image where sulfur accumulates in a plant grown in sulfur-contaminated soil, and reveal the different forms of sulfur present in a soil sample, to name a few examples. Read more at:


SSRL Headlines is published electronically monthly to inform SSRL users, sponsors and other interested people about happenings at SSRL. SSRL is a national synchrotron user facility operated by Stanford University for the U.S. Department of Energy Office of Basic Energy Sciences. Additional support for the structural biology program is provided by the DOE Office of Biological and Environmental Research, the NIH National Center for Research Resources and the NIH Institute for General Medical Sciences. Additional information about SSRL and its operation and schedules is available from the SSRL WWW site.


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Last Updated: 31 August 2010
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