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The BABAR Collaboration BABAR, the detector for the SLAC PEP-II asymmetric e + e − B Factory operating at the Υ (4S) resonance, was designed to allow comprehensive studies of CP -violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagnetic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by dE/dx measurements in the tracking detectors and in a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems , VME-and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.

The reduction of CO2 on tin cathodes was studied using in situ attenuated total reflectance infrared spectroscopy (ATR-IR). Thin films of a mixed Sn/SnO x species were deposited onto a single-crystal ZnSe ATR crystal. Peaks centered at about 1500, 1385, and 1100 cm–1, attributed to a surface-bound monodentate tin carbonate species, were consistently present under conditions at which CO2 reduction takes place. It was shown that these peaks are only present at potentials where CO2 reduction is observed. Moreover, these peaks disappear if the pH of the reaction is too low or if the tin surface is chemically etched to remove surface oxide. Sn6O4(OH)4 and SnO2 nanoparticles were shown to be catalytically active for CO2 reduction, and insights into the oxidation state of the catalytically active species are gained from a comparison of the catalytic behavior of the two nanoparticle species. From these experiments, a mechanism governing the reduction of CO2 on tin electrodes is proposed.

The interactions of CO2 with indium metal electrodes have been characterized for electrochemical formate production. The electrode oxidation state, morphology, and voltammetric behaviors were systematically probed. It was found that an anodized indium electrode stabilized formate production over time compared to etched indium electrodes and indium electrodes bearing a native oxide in applied potential range of -1.4 to -1.8 V vs SCE. In addition, it was observed that formate is the major product at unprecedentedly low overpotentials at the anodized surface. A surface hydroxide species was observed suggesting a mechanism of formate production that involves insertion of CO2 at the indium interface to form an electroactive surface bicarbonate species.

Knowledge and foundational understanding of phenomena associated with the behavior of materials at the nanoscale is one of the key scientific challenges toward a sustainable energy future. Size reduction from bulk to the nanoscale leads to a variety of exciting and anomalous phenomena due to enhanced surface-to-volume ratio, reduced transport length, and tunable nanointerfaces. Nanostructured metal hydrides are an important class of materials with significant potential for energy storage applications. Hydrogen storage in nanoscale metal hydrides has been recognized as a potentially transformative technology, and the field is now growing steadily due to the ability to tune the material properties more independently and drastically compared to those of their bulk counterparts. The numerous advantages of nanostructured metal hydrides compared to bulk include improved reversibility, altered heats of hydrogen absorption/desorption, nanointerfacial reaction pathways with faster rates, and new surface states capable of activating chemical bonds. This review aims to summarize the progress to date in the area of nanostructured metal hydrides and intends to understand and explain the underpinnings of the innovative concepts and strategies developed over the past decade to tune the thermodynamics and kinetics of hydrogen storage reactions. These recent achievements have the potential to propel further the prospects of tuning the hydride properties at nanoscale, with several promising directions and strategies that could lead to the next generation of solid-state materials for hydrogen storage applications.

The neutron longitudinal and transverse asymmetries A n 1 and A n 2 have been extracted from deep inelastic scattering of polarized electrons by a polarized 3 He target at incident energies of 19.42, 22.66 and 25.51 GeV. The measurement allows for the determination of the neutron spin structure functions g n 1 (x; Q 2 ) and g n 2 (x; Q 2 ) over the range 0:03 < x < 0:6 at an average Q 2 of 2 (GeV=c) 2 . The data are used for the evaluation of the Ellis-Ja e and Bjorken sum rules. The neutron spin structure function g n 1 (x; Q 2 ) is small and negative within the range of our measurement, yielding an integral R 0:6 0:03 g n 1 (x)dx = 0:028 0:006 (stat) 0:006 (syst). Assuming Regge behavior at low x, we extract n 1 =

Abstract:The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-rayinduced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs. ©2010 Optical Society of America

Molecules can efficiently and selectively convert light energy into other degrees of freedom. Disentangling the underlying ultrafast motion of electrons and nuclei of the photoexcited molecule presents a challenge to current spectroscopic approaches. Here we explore the photoexcited dynamics of molecules by an interaction with an ultrafast X-ray pulse creating a highly localized core hole that decays via Auger emission. We discover that the Auger spectrum as a function of photoexcitation-X-ray-probe delay contains valuable information about the nuclear and electronic degrees of freedom from an element-specific point of view. For the nucleobase thymine, the oxygen Auger spectrum shifts towards high kinetic energies, resulting from a particular C-O bond stretch in the pp* photoexcited state. A subsequent shift of the Auger spectrum towards lower kinetic energies displays the electronic relaxation of the initial photoexcited state within 200 fs. Ab-initio simulations reinforce our interpretation and indicate an electronic decay to the np* state.