APPELS, differentially pumped Ambient Pressure PhotoElectron Lens System for photoemission studies, is one of four inventions from the US Department of Energy’s Lawrence Berkeley National Laboratory which have been recognised with the R&D 100 award for 2010 from R&D Magazine, which recognises the 100 most significant proven technological advances of the year.

An international collaboration that included Berkeley Lab scientists Frank Ogletree, Hendrik Bluhm, Zahid Hussain and Miquel Salmeron, working at Berkeley Lab’s Advanced Light Source (ALS), developed a novel lens system that makes possible the use of X-ray Photoelectron Spectroscopy technology under pressures and humidities similar to those encountered in the natural environment. Called the Ambient Pressure PhotoElectron Lens System (APPELS), this new technique has already led to groundbreaking discoveries in climate change, atmospheric science, nanotechnology and industrial processes, such as heterogeneous catalysis. Also part of the collaboration were SPECS GmbH, a German firm that designs and produces surface analysis instruments, and Robert Schlögl of the Franz Haber Institute of the Max Planck Society.

X-ray Photoelectron Spectroscopy (XPS) is typically performed in a vacuum or at pressures below 4.6 torr, which is the scientifically and technically important vapour pressure of water at the triple point and the critical threshold pressure for environmental science studies. Through a technique called pressure differential pumping, the APPELS technology allows measurements at pressures of more than 10 torr. This enables investigators using APPELS to improve climate change models, ward off the damaging effects of humidity on nanosystems, provide insights into the impact of chemicals on agricultural plants and human health, and aid in controlling the pollution of air, water and other environmental systems. With APPELS, it is possible to observe chemical interactions at the atomic level for gas/liquid and liquid/solid interfaces at ambient pressures.

APPELS is now part of XPS instruments being used on two beamlines at the ALS, and on beamlines at other synchrotrons around the world, including the National Synchrotron Light Source at Brookhaven National Laboratory, BESSY and the Centre for Synchrotron Radiation in Germany, the MAX-lab synchrotron in Sweden, and the ALBA synchrotron in Spain. In addition, Sweden’s Gammadata is offering an instrument that relies on APPELS technology. APPELS was developed with support from the US DOE’s Office of Science, with additional support from Berkeley Lab’s Laboratory Directed Research and Development (LDRD) programme.

Said Cheryl Fragiadakis, who heads Berkeley Lab’s Technology Transfer and Intellectual Property Management Department, which nominated the technologies: “This year’s winners from Berkeley Lab embody the high quality research and focus on impactful application that are the hallmark of our work. It is terrific to have the additional recognition conferred by the R&D 100 awards. I join with the rest of Berkeley Lab in congratulating our staff and our partners!”

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