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.

Laboratory observation of oligomers in the aerosol from isoprene/NOx photooxidation

Abstract: [1] Compounds assigned to be oxidation products of isoprene (2-methyl-1,3-butadiene) have recently been observed in ambient aerosols, suggesting that isoprene might play an important role in secondary organic aerosol (SOA) formation due to its large global source strength. SOA yields from photooxidation of isoprene and NOx in a chamber agree fairly well with previous data. Matrix assisted laser desorption/ionization mass spectrometry showed the formation of high molecular weight compounds over the course of 15-hour experiments. Concurrently, the volatility of the SOA decreased markedly as observed by a tandem differential mobility analyzer. The volume fraction remaining of SOA at 150°C increased steadily from 5 to 25% during the same experiments. These observations are attributed to oligomerization reactions occurring in the aerosol phase. Under dry conditions a lower volatility was observed.

Fast Chemical Imaging at High Spatial Resolution by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Abstract: In recent years, chemical imaging was prognosticated to become one of the key analytical applications for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). However, moderate spatial resolution and the associated measurement time required for a larger sampling area, have restricted this versatile, high sensitivity technique from being routinely used in two-dimensional chemical imaging. This work describes the development and investigation of a low dispersion sample chamber (tube cell), which allows improvement of the imaging capabilities by reduction of the single LA shot duration to 30 ms (full width at 1% maximum). The new tube cell is based on a constant laminar flow and a well-controlled delivery of the laser-ablated aerosol into the transport system, leading to minimized tailing of the aerosol washout and helping to separate the signals even at repetition rates as high as 20–30 Hz. To demonstrate the improved imaging capabilities, microstructured metallic thin film patterns were...

Comparison of electronic structure and template function of single-layer graphene and a hexagonal boron nitride nanomesh on Ru(0001)

Abstract: The structure of a single-layer graphene on Ru(0001) is compared with that of a single-layer hexagonal boron nitride nanomesh on Ru(0001). Both are corrugated $s{p}^{2}$ hybridized networks and display a $\ensuremath{\pi}$ band gap at the $\overline{\text{K}}$ point of their $1\ifmmode\times\else\texttimes\fi{}1$ Brillouin zone. In contrast to $h\text{-BN}/\text{Ru}(0001)$, $g/\text{Ru}(0001)$ has a distinct Fermi surface. Together with the band structure measurements this indicates that $0.1e$ per $1\ifmmode\times\else\texttimes\fi{}1$ unit cell are transferred from the Ru substrate to the graphene. Photoemission from adsorbed xenon on $g/\text{Ru}(0001)$ identifies two $\text{Xe}\text{ }5{p}_{1/2}$ lines, separated by 240 meV, which reveals a corrugated electrostatic potential energy surface like on $h\text{-BN}/\text{Rh}(111)$. These two Xe species are related to the topography of the template and have different desorption energies.

Implementation of a fast method for high resolution phase contrast tomography

Abstract: We report the implementation of a method which can yield the 3D distribution of the phase (refractive index) of a weakly absorbing object from a single tomographic data set. In order to reduce the residual absorption artifact (due to the fact that only one data set is used) the original algorithm presented by A. V. Bronnikov is amended by adding in the filter a factor found by using a semi empirical approach. The quality of the reconstruction is largely sufficient for optimal segmentation and further postprocessing even though the filter correction is based on assumption of constant absorption. This one step approach allows keeping radiation dose to the minimum. Spatial resolution is comparable to the conventional absorption based technique. The performance of the method is validated by using an established phase contrast technique.

Revising the hygroscopicity of inorganic sea salt particles.

Abstract: Sea spray is one of the largest natural aerosol sources and plays an important role in the Earth's radiative budget. These particles are inherently hygroscopic, that is, they take-up moisture from the air, which affects the extent to which they interact with solar radiation. We demonstrate that the hygroscopic growth of inorganic sea salt is 8-15% lower than pure sodium chloride, most likely due to the presence of hydrates. We observe an increase in hygroscopic growth with decreasing particle size (for particle diameters <150 nm) that is independent of the particle generation method. We vary the hygroscopic growth of the inorganic sea salt within a general circulation model and show that a reduced hygroscopicity leads to a reduction in aerosol-radiation interactions, manifested by a latitudinal-dependent reduction of the aerosol optical depth by up to 15%, while cloud-related parameters are unaffected. We propose that a value of κs=1.1 (at RH=90%) is used to represent the hygroscopicity of inorganic sea salt particles in numerical models.