From the Director
SSRL is very proud to have joined other light sources around the world in running the facility and a few specific beam lines to enable COVID-19 related research. Despite the general shutdown as a result of a shelter-in-place rule, we are as of present operating SPEAR3 and three (soon to be four) stations – BLs 12-2 and 9-2 for macromolecular crystallography, 4-2 for biological small-angle x-ray scattering, and 6-2 for TXM studies, all in support of avenues to address the pandemic in various ways. Unfortunately but understandably, we cannot provide any definitive prediction as for when SSRL will resume normal user operations. While SLAC has initiated a planning process for gradual site opening, including a phased startup of SSRL operations, at this point we have no definite date, and are looking ahead a couple of weeks at a time. We urge you to check our website weekly for updated announcements, and ask for your patience and understanding.
Science Highlights
Discovery of Topological Weyl Fermion Lines and Drumhead Surface States in a Room Temperature Magnet – Contacts: Ilya Belopolski and M. Zahid Hasan, Princeton University
Physicists have been interested in crystalline materials where the quantum mechanical behavior of electrons is governed by topology, so-called topological quantum matter. Recently the community has been particularly excited about crystals which additionally exhibit magnetism, i.e. topological quantum magnets. What new topological behavior might such magnets exhibit? Can we find examples of such exotic quantum magnets in nature? And could magnetic topological phases of matter lead to insights about fundamental questions in science or pave the way to technological applications? Read more...
Shedding Light on Photoisomerization: Electrostatic Control of Excited State Reaction Pathways within Proteins – Contact: Stephen G. Boxer, Stanford University
Organisms including microbes, plants, and animals can interpret light as a signal for action. While this is a fundamental and important process, the mechanism still holds mystery. How are photons converted into molecular signals? At the most basic step, a light-sensing molecule, a chromophore, undergoes a conformational change, an isomerization, when it encounters a photon. Many details are still unknown, which impacts efforts to engineer artificial light-sensing systems based on natural systems. A team of scientists has illuminated the importance of the immediate electrostatic environment of the chromophore on photoisomerization. Read more...
