Paul Scherrer Institute

About: Paul Scherrer Institute is a facility organization based out in Villigen, Switzerland. It is known for research contribution in the topics: Neutron & Large Hadron Collider. The organization has 9248 authors who have published 23984 publications receiving 890129 citations. The organization is also known as: PSI.

Spin structure of the Shockley surface state on Au ( 111 )

Abstract: The free-electron like surface state on the (111) surface of gold shows a splitting into two parabolic subbands induced by the spin orbit interaction. Spin-resolved high-resolution photoemission experiments performed with a full three-dimensional spin polarimeter provide a detailed image of the resulting spin structure. In particular, spin-resolved momentum distribution maps show that the spin vector lies in the surface plane and is perpendicular to the momentum of the electrons as expected in a free-electron model. This method of measuring the spin structure of a two-dimensional electron gas allows the observation of the direction of electric fields as probed by the electrons. Although the energy splitting can only be understood as a consequence of strong atomic electric fields, no modulation of the spin direction due to these fields is detected.

Controlling spins in adsorbed molecules by a chemical switch

Abstract: The development of chemical systems with switchable molecular spins could lead to the architecture of materials with controllable magnetic or spintronic properties. Here, we present conclusive evidence that the spin of an organometallic molecule coupled to a ferromagnetic substrate can be switched between magnetic off and on states by a chemical stimulus. This is achieved by nitric oxide (NO) functioning as an axial ligand of cobalt(II)tetraphenylporphyrin (CoTPP) ferromagnetically coupled to nickel thin-film (Ni(001)). On NO addition, the coordination sphere of Co(2+) is modified and a NO-CoTPP nitrosyl complex is formed, which corresponds to an off state of the Co spin. Thermal dissociation of NO from the nitrosyl complex restores the on state of the Co spin. The NO-induced reversible off-on switching of surface-adsorbed molecular spins observed here is attributed to a spin trans effect.

A mass spectrometric study of secondary organic aerosols formed from the photooxidation of anthropogenic and biogenic precursors in a reaction chamber

Abstract: An Aerodyne Aerosol Mass Spectrometer (AMS) has been utilised to provide on-line measurements of the mass spectral signatures and mass size distributions of the oxidation products resulting from irradiating 1,3,5- trimethylbenzene (1,3,5-TMB) and -pinene, separately, in the presence of nitrogen oxide, nitrogen dioxide and propene in a reaction chamber. Mass spectral results indicate that both precursors produce SOA with broadly similar chemi- cal functionality of a highly oxidised nature. However, sig- nificant differences occur in the minor mass spectral frag- ments for the SOA in the two reaction systems, indicating that they have different molecular composition. Nitrogen- containing organic compounds have been observed in the photooxidation products of both precursors, and their for- mation appeared to be controlled by the temporal variabil- ity of NOx. Although the overall fragmentation patterns of the photooxidation products in both systems did not change substantially over the duration of each experiment, the con- tribution of some individual mass fragments to total mass appeared to be influenced by the irradiation time. The ef- fective densities of the 1,3,5-TMB and -pinene SOA parti- cles were determined for various particle sizes using the re- lationship between mobility and vacuum aerodynamic diam- eters. The effective density for the 1,3,5-TMB SOA ranged from 1.35-1.40g/cm 3 , while that for -pinene SOA ranged from 1.29-1.32g/cm 3 . The determined effective densities did not show dependence on irradiation time. Results sug- gest that further chemical processing of SOA takes place in the real atmosphere, as neither the -pinene nor the 1,3,5- TMB experimental results reproduce the right relative prod- uct distribution between carbonyl-containing and multifunc- tional carboxylic acid species measured at ambient locations influenced by aged continental organic aerosols.

IrO2-TiO2: A High-Surface-Area, Active, and Stable Electrocatalyst for the Oxygen Evolution Reaction

Abstract: The utilization and development of efficient water electrolyzers for hydrogen production is currently limited due to the sluggish kinetics of the anodic process—the oxygen evolution reaction (OER). Moreover, state of the art OER catalysts contain high amounts of expensive and low-abundance noble metals such as Ru and Ir, limiting their large-scale industrial utilization. Therefore, the development of low-cost, highly active, and stable OER catalysts is a key requirement toward the implementation of a hydrogen-based economy. We have developed a synthetic approach to high-surface-area chlorine-free iridium oxide nanoparticles dispersed in titania (IrO2-TiO2), which is a highly active and stable OER catalyst in acidic media. IrO2-TiO2 was prepared in one step in molten NaNO3 (Adams fusion method) and consists of ca. 1–2 nm IrO2 particles distributed in a matrix of titania nanoparticles with an overall surface area of 245 m2 g–1. This material contains 40 molM % of iridium and demonstrates improved OER activi...