Classical two-slit interference effects in double photoionization of molecular hydrogen at high energies

Recent experiments on double photoionization of H2 with photon energies between 160 and 240 eV have revealed body-frame angular distributions that suggest classical two-slit interference effects may be present when one electron carries most of the available energy and the second electron is not observed. We report precise quantum mechanical calculations that reproduce the experimental findings. They reveal that the interpretation in terms of classical diffraction is only appropriate at substantially higher photon energies. At the energies considered in the experiment we offer an alternative explanation based on the mixing of two nondiffractive contributions by circularly polarized light.     

Images of biological samples undergoing sterilization by a glowdischarge at atmospheric pressure

Among the various industrial uses of the glow discharge at atmospheric pressure (GDAP), biological applications such as sterilization are under investigation. In this paper, we present images of a liquid medium (Luria-Bertani broth with tetracycline) contaminated by Escherichia coli bacteria (strain PER 322) undergoing plasma treatment. In most cases, it is found that an exposure time of two to 20 minutes leads to nearly a complete kill of a 10⁸/ml E. coli population. The treatment time necessary to obtain a complete kill depends on the plasma power density, the type of gas used, the type of bacteria, and the type of medium     

Mode specificity of unimolecular rate constants in the Hénon-Heiles system

The tunneling widths of high-energy metastable states lying in the classical irregular region of the Hénon-Heiles potential energy surface were calculated via complex analytical continuation of stabilization graphs. Mode specificity is demonstrated in that the lifetimes of normal-mode, local-bond-mode, and mode-mixed states at nearby energies differ by an order of magnitude.     

Ultra‐performance liquid chromatography tandem mass spectrometry method for the determination of AZ66, a sigma receptor ligand,in rat plasma and its application to in vivo pharmacokinetics

Methamphetamine abuse continues as a major problem in the USA owing to its powerful psychological addictive properties. AZ66, 3‐[4‐(4‐cyclohexylpiperazine‐1‐yl)pentyl]‐6‐fluorobenzo[d]thiazole‐2(3H)‐one, an optimized sigma receptor ligand, is a promising therapeutic agent against methamphetamine. To study the in vivo pharmacokinetics of this novel sigma receptor ligand in rats, a sensitive ultra‐performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) method was developed in rat plasma and validated. The developed method requires a small volume of plasma (100 μL) and a simple liquid–liquid extraction. The chromatographic separations were achieved in 3.3 min using an Acquity UPLC BEH Shield RP₁₈ column. The mass spectrophotometric detection was carried out using a Waters Micromass Quattro MicroTM triple‐quadrupole system. Multiple reaction monitoring was used for the quantitation with transitions m/z 406 → m/z 181 for AZ66 and m/z 448 → m/z 285 for aripiprazole. The method was validated over a concentration range of 1–3500 ng/mL and the lower limit of quantitation was determined to be 1 ng/mL. Validation of the assay demonstrated that the developed UPLC/MS/MS method was sensitive, accurate and selective for the determination of AZ66 in rat plasma. The present method has been successfully applied to an i.v. pharmacokinetic study in Sprague–Dawley rats. Copyright © 2013 John Wiley & Sons, Ltd.     

Construction of complex STO-NG basis sets by the method of least squares and their applications

The goals of electronic structure theory are to make quantitative predictions of molecular properties and to provide qualitative insight into bonding as well as features of potential energy surfaces. Oftentimes, the two goals are at odds as an accurate treatment requires a complicated wave function that obscures chemical insight. The multifacet graphically contracted function (MFGCF) method offers a new approach that allows both goals to be addressed simultaneously. The recursive product structure of the MFGCF wave function reduces the exponential scaling of the exact wave function and allows the computation of molecular properties with polynomial scaling with respect to system size. Additionally, the graph density concept provides an intuitive tool for visualizing and analyzing the qualitative features of the wave function. In this work, the graph densities for model systems are examined to demonstrate their utility in analyzing the changes in wave function character along potential energy surfaces and near avoided crossings. Finally, we demonstrate that the graph density exposes the structure of the exact wave function for a system of noninteracting molecules as a product of the fragment wave functions.     

Titrimetric determination of hydrogen peroxide in alkaline solution

Direct titration of hydrogen peroxide in alkaline bromide media has been accomplished with sodium hypochlorite. The relative standard deviation is 0.2%. A photometric end-point is recommended for the determination of 0.10-1.0 mequiv of peroxide. Larger samples are evaluated by use of Bordeaux Red as visual indicator. The hypochlorite procedure compares favourably with iodometry and permanganate in the analysis of commercial peroxides.     

Heat capacities of aqueous perchloric acid and sodium perchlorate at 298°K: ΔC p o of ionization of water

We have used a Picker flow calorimeter for measurements leading to apparent molal heat capacities of dilute aqueous solutions of HClO₄ and NaClO₄ at 298°K. Results have been used to derive _c ^° =–27.1J-°K ^–1-mole ^–1 for HClO₄ (aq.), _c ^° =15.2J-°K ^–1-mole ^–1 for NaClO₄ (aq.), and C _p=–213.₈J-°K^–1-mole^–1 for ionization of water.