Environmental Molecular Sciences Laboratory

About: Environmental Molecular Sciences Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Mass spectrometry & Ion. The organization has 1471 authors who have published 3010 publications receiving 169961 citations.

Ab Initio Study of M+:18-Crown-6 Microsolvation

Abstract: The effect of aqueous microsolvation on the relative binding affinities of 18-crown-6 for the alkali metal cations (Li+−Cs+) was studied using second-order perturbation theory and polarized basis sets augmented with diffuse functions to minimize basis set superposition error. A cation exchange reaction involving the replacement of potassium in a cation/crown complex with a different alkali cation contained within a cation/water cluster served as the basis for modeling binding preferences in liquid water. Up through four crown ether waters of solvation (six for Li+ and K+) were considered, in conjunction with cation/water complexes including as many as nine waters. The principal impact of the added waters on the K+ ↔ M+ exchange reaction was to sharply reduce the spread in binding enthalpies among the different elements, narrowing the discrepancy between the theoretical gas phase cluster results and experimental findings obtained in aqueous solutions.

Implementing an accurate and rapid sparse sampling approach for low-dose atomic resolution STEM imaging

Abstract: While aberration correction for scanning transmission electron microscopes (STEMs) dramatically increased the spatial resolution obtainable in the images of materials that are stable under the electron beam, the practical resolution of many STEM images is now limited by the sample stability rather than the microscope. To extract physical information from the images of beam sensitive materials, it is becoming clear that there is a critical dose/dose-rate below which the images can be interpreted as representative of the pristine material, while above it the observation is dominated by beam effects. Here, we describe an experimental approach for sparse sampling in the STEM and in-painting image reconstruction in order to reduce the electron dose/dose-rate to the sample during imaging. By characterizing the induction limited rise-time and hysteresis in the scan coils, we show that a sparse line-hopping approach to scan randomization can be implemented that optimizes both the speed of the scan and the amount of the sample that needs to be illuminated by the beam. The dose and acquisition time for the sparse sampling is shown to be effectively decreased by at least a factor of 5× relative to conventional acquisition, permitting imaging of beam sensitive materials to be obtained without changing the microscope operating parameters. The use of sparse line-hopping scan to acquire STEM images is demonstrated with atomic resolution aberration corrected the Z-contrast images of CaCO3, a material that is traditionally difficult to image by TEM/STEM because of dosage issues.

Electronic structure of small copper oxide clusters: From Cu 2 O to Cu 2 O 4

Abstract: We study the electronic structure of copper oxide clusters, ${\mathrm{Cu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ (x=1\char21{}4), using anion photoelectron spectroscopy and density-functional calculations. The experiment is used to successfully guide a computational search for the cluster geometries. The predicted electron affinities at the obtained cluster structures reproduce exactly the trend observed experimentally. The definitive determination of the cluster structures enables a detailed analysis of the chemical bonding and electronic structure involving Cu atoms in different oxidation states exhibited by these clusters. \textcopyright{} 1996 The American Physical Society.