Interpretation of Polarized Absorption and Emission Spectra of Molecules Incorporated in Stretched Polymer Films

Different methods for the interpretation of linear dichroic spectra of molecules incorporated in uniaxial matrices are discussed. A method based on the combination of both polarized absorption and emission measurements is described for the resolution of absorption and emission spectra into their different polarized components, and for the investigation of molecular distributions in the oriented matrix. The distributions of some planar molecules of different shapes incorporated in stretched polyethylene films are presented.     

X‐ray photoelectron spectroscopy process optimization for characterization of trace contamination elements for extreme ultraviolet resist outgassing study

X‐ray photoelectron spectroscopy (XPS) is used for elemental identification and quantification in a number of fields, and the optimization of XPS performance can help in making better use of the limited XPS tool availability. In the field of extreme ultraviolet (EUV) lithography, one of the requirements is having a clean vacuum environment to minimize contamination of the EUV optics. EUV resist outgassing is viewed as one of the main issues that could affect the vacuum environment. There is a program underway to measure the relative contamination rates from different resists following the ASML (provider of lithography systems) approved protocols for witness plate testing. One of the key steps is the XPS measurement of residue on the optics after cleaning. The role of XPS in quantification of species that adhere to the ruthenium‐coated silicon witness plate sample is discussed. The various XPS tool parameters like the pass energy and source setting were optimized for our application of witness plate analysis. The statistics of our XPS tool were studied, and combined with the fundamental XPS equations, a simple mathematical model was developed to optimize the number of scans for the various elements of interest in our witness plate study. Using the optimized number of scans, the acquisition time to measure the contaminant elements to a precision better than 0.1 at.% was minimized. The model devised in the paper can be adapted to other XPS measurements requiring different levels of precision. Copyright © 2013 John Wiley & Sons, Ltd.     

Event-shape-engineering study of charge separation in heavy-ion collisions

Recent measurements of charge-dependent azimuthal correlations in high-energy heavy-ion collisions have indicated charge-separation signals perpendicular to the reaction plane, and have been related to the chiral magnetic effect(CME). However, the correlation signal is contaminated with the background caused by the collective motion(flow) of the collision system, and an effective approach is needed to remove the flow background from the correlation. We present a method study with simplified Monte Carlo simulations and a multi-phase transport model,and develop a scheme to reveal the true CME signal via event-shape engineering with the flow vector of the particles of interest.     

MOVIPAC: Vibrational spectroscopy with a robust meta‐program for massively parallel standard and inverse calculations

We present the software package MO VI PAC for calculations of vibrational spectra, namely infrared, Raman, and Raman Optical Activity (ROA) spectra, in a massively parallelized fashion. MO VI PAC unites the latest versions of the programs SNF and AKIRA alongside with a range of helpful add‐ons to analyze and interpret the data obtained in the calculations. With its efficient parallelization and meta‐program design, MO VI PAC focuses in particular on the calculation of vibrational spectra of very large molecules containing on the order of a hundred atoms. For this purpose, it also offers different subsystem approaches such as Mode‐ and Intensity‐Tracking to selectively calculate specific features of the full spectrum. Furthermore, an approximation to the entire spectrum can be obtained using the Cartesian Tensor Transfer Method. We illustrate these capabilities using the example of a large π‐helix consisting of 20 (S)‐alanine residues. In particular, we investigate the ROA spectrum of this structure and compare it to the spectra of α‐ and 3₁₀‐helical analogs. © 2012 Wiley Periodicals, Inc.     

Electrochemical determination of thermodynamic properties of DyRhO3 and phase relations in the system Dy-Rh-O

Thermodynamic properties of Dysprosium rhodite (DyRhO₃) are measured in the temperature range from 900 to 1,300 K using a solid-state electrochemical cell incorporating yttria-stabilized zirconia as the electrolyte. The standard Gibbs free energy of formation of DyRhO₃ with O-type perovskite structure from its components binary oxides, Dysprosia with C-rare earth structure and β-Rh₂O₃ with orthorhombic structure, can be represented by the equation: $$ {{{\varDelta G_{{f\left( {ox} \right)}}^o\left( {\pm 182} \right)}} \left/ {{{\mathrm{J} ~ \mathrm{mo}}{{\mathrm{l}}^{{ - 1}}}}} \right.} = - 52710 + 3.821\left( {{{T} \left/ {\mathrm{K}} \right.}} \right). $$ By using the thermodynamic data for DyRhO₃ from experiment and auxiliary data for other phases from the literature, the phase relations in the system Dy-Rh-O are computed. Thermodynamic data for intermetallic phases in the binary system Dy-Rh, required for constructing the chemical potential diagrams, are evaluated using calorimetric data available in the literature for three intermetallics and Miedema’s model, consistent with the phase diagram. The results are presented in the form of Gibbs triangle, oxygen potential–composition diagram, and three-dimensional chemical potential diagram at 1,273 K. Temperature–composition diagrams at constant oxygen partial pressures are also developed. The decomposition temperature of DyRhO₃ is 1,732 (±2.5) K in pure oxygen and 1,624 (±2.5) K and in air at standard pressure.     

Chlorine‐Enhanced Surface Mobility of Au(100)

Motivated by experimental studies of two‐dimensional Ostwald ripening on Au(100) electrodes in chlorine‐containing electrolytes, we have studied diffusion processes using density functional theory. We find that chlorine has a propensity to temporary form AuCl complexes, which diffuse significantly faster than gold adatoms. With and without chlorine, the lowest activation energy is found for the exchange mechanism. Chlorine furthermore reduces the activation energy for the detachment from kink sites. Kinetic Monte Carlo simulations were performed on the basis of extensive density functional theory calculations. The island‐decay rate obtained from these Monte Carlo simulations, as well as the decay rate obtained from the theoretical activation energies and frequency factors when inserted into analytical solutions for Ostwald ripening, are in agreement with experimental island‐decay rates in chlorine‐containing electrolytes.     

The effect of optical substrates on micro-FTIR analysis of single mammalian cells

The study of individual cells with infrared (IR) microspectroscopy often requires living cells to be cultured directly onto a suitable substrate. The surface effect of the specific substrates on the cell growth—viability and associated biochemistry—as well as on the IR analysis—spectral interference and optical artifacts—is all too often ignored. Using the IR beamline, MIRIAM (Diamond Light Source, UK), we show the importance of the substrate used for IR absorption spectroscopy by analyzing two different cell lines cultured on a range of seven optical substrates in both transmission and reflection modes. First, cell viability measurements are made to determine the preferable substrates for normal cell growth. Successively, synchrotron radiation IR microspectroscopy is performed on the two cell lines to determine any genuine biochemically induced changes or optical effect in the spectra due to the different substrates. Multivariate analysis of spectral data is applied on each cell line to visualize the spectral changes. The results confirm the advantage of transmission measurements over reflection due to the absence of a strong optical standing wave artifact which amplifies the absorbance spectrum in the high wavenumber regions with respect to low wavenumbers in the mid-IR range. The transmission spectra reveal interference from a more subtle but significant optical artifact related to the reflection losses of the different substrate materials. This means that, for comparative studies of cell biochemistry by IR microspectroscopy, it is crucial that all samples are measured on the same substrate type.

Chemoselective hydrosilylation of hydroxyketones

A chemoselective method for the hydrosilylation of ketones has been developed, using the combination of triphenylsilane and a catalyst prepared from Ni(COD)₂ and the simple N-heterocyclic carbene IMes. The most notable feature of this method is that free hydroxyls are largely unaffected, thus providing a simple one-step procedure for the conversion of hydroxyketones to mono-protected diols, wherein the protecting group is exclusively installed on the ketone-derived hydroxyl. The process is typically high yielding with both simple ketones and more complex hydroxyketone substrates.