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Journal of Physical Chemistry. A

Stefan Mebs, Jens Beckmann
Calculations of real-space bonding indicators (RSBI) derived from Atoms-In-Molecules (AIM), Electron-Localizability-Indicator (ELI-D), Non-Covalent-Interactions index (NCI), and Density-Overlap-Regions-Indicator (DORI) toolkits for a set of 36 donor acceptor complexes X3BNY3 (1, 1a-1h), X3AlNY3 (2, 2a-2h), X3BPY3 (3, 3a-3h) and X3AlPY3 (4, 4a-4h) reveal that the donor-acceptor bonds are comprised of covalent and ionic interactions in varying extents (X = Y = H for 1-4; X = H, Y = Me for 1a-4a; X = H, Y = Cl for 1b-4b; X = Me, Y = H for 1c-4c; X, Y = Me for 1d-4d; X = Me, Y = Cl for 1e-4e; X = Cl, Y = H for 1f-4f; X = Cl, Y = Me for 1g-4g; X, Y = Cl for 1h-4h)...
September 15, 2017: Journal of Physical Chemistry. A
John C Walton
Comparison of accepted pKa values of bicarbonate, carboxyl and hydroperoxyl radicals, with those of models having the unpaired electron replaced by H-atoms, implied the acidity of the radicals was greatly increased. A DFT computational method of estimating pKas was developed and applied to a set of radicals designed to probe the phenomenon of Radical-Enhanced Deprotonation (RED-shift) and its underlying causes. Comparison of the computed pKa values of twelve acid radicals to those of the corresponding model acids confirmed the intensified acidity of the title radicals and also pin-pointed the carboxy-ethynyl (HO2CCC•) and the carboxy-aminyl (HO2CNH•) radicals as having enhanced acidity...
September 15, 2017: Journal of Physical Chemistry. A
Robert Georges, Xavier Michaut, Audrey Moudens, Manuel Goubet, Olivier Pirali, Pascale Soulard, Pierre Asselin, Therese R Huet, Pascale Roy, Martin Fournier, Andrey A Vigasin
We report the results of an experimental study related to the relaxation of the nuclear spin isomers of the water molecule in a supersonic expansion. Rovibrational lines of both ortho- and para- spin isomers were recorded in the spectral range of H2O stretching vibrations around 3700 cm(-1) using FTIR direct absorption. Water vapor seeded either in argon, helium, oxygen or in a mixture of oxygen and argon was expanded into vacuum through a slit nozzle. Partial water vapor pressure in the mixture varied in a wide range from 1...
September 15, 2017: Journal of Physical Chemistry. A
V P Bulychev, M V Buturlimova, K G Tokhadze
The geometrical parameters, the frequencies, and absolute intensities of vibrational transitions of H2O···trans-HONO hydrogen-bonded complex are calculated using the approach earlier tested in calculations of isolated molecules of nitrous acid and complexes of this acid with ammonia. The equilibrium nuclear configuration and potential energy and dipole moment surfaces are calculated by the MP2/aug-cc-pVTZ method with the basis set superposition error taken into account. The fundamental transition frequencies and intensities of the complex are first obtained in the harmonic approximation, and then the energy values, vibrational wave functions, and transition frequencies and intensities are determined from variational solutions of one- to four-dimensional anharmonic equations...
September 15, 2017: Journal of Physical Chemistry. A
Maurizio Coden, Enrico Nale, Giorgio J Moro, Barbara Fresch
We study an ensemble of quantum pure states, the thermalization resilient ensemble (TRE), providing the statistical characterization of the thermal equilibrium of isolated quantum systems. Following a previous work where the ensemble was defined based on the invariance of the average populations upon thermal contact of identical systems, here we introduce a general methodology to generate quantum states according to the TRE statistic. The sampling is employed to characterize the ensemble distribution of thermodynamic functions like the entropy, internal energy, and temperature...
September 15, 2017: Journal of Physical Chemistry. A
Chandan Kumar, Heike Fliegl, Dage Sundholm
Magnetically induced ring-current strength susceptibilities and nucleus independent chemical shifts (NICS) have been studied for 15 single-ring aromatic, antiaromatic, and nonaromatic molecules. The current densities have been calculated at the density functional theory (DFT), Hartree-Fock (HF) theory, and second-order Møller-Plesset perturbation theory (MP2) levels using the gauge-including magnetically induced current method (GIMIC). The ring-current strength susceptibilities have been obtained by numerical integration of the current density flowing around the molecular ring...
September 15, 2017: Journal of Physical Chemistry. A
Zhi Gao, Sjoerd N Vogels, Matthieu Besemer, Tijs Karman, Gerrit C Groenenboom, Ad Van der Avoird, Sebastiaan Y T van de Meerakker
We present state-to-state differential cross sections for collisions of NO molecules (X(2)Π1/2, j=1/2f) with para-H2 and ortho-D2 molecules, at a collision energy of 510 and 450 cm(-1), respectively. The angular scattering distributions for various final states of the NO radical are measured with high resolution using a crossed molecular beam apparatus that employs the combination of Stark deceleration and velocity map imaging. Rotational rainbows as well as diffraction oscillations are fully resolved in the scattering images...
September 14, 2017: Journal of Physical Chemistry. A
AnGayle K Vasiliou, Hui Hu, Thomas W Cowell, Jared C Whitman, Jessica Porterfield, Carol A Parish
The thermal decomposition mechanism of thiophene has been investigated both experimentally and theoretically. Thermal decomposition experiments were done using a 1 mm x 3 cm pulsed silicon carbide microtubular reactor, Unlike previous studies these experiments were able to identify the initial thiophene decomposition products. Thiophene was entrained in either Ar, Ne or He carrier gas, passed through a heated (300-1700 K) SiC microtubular reactor (roughly ≤100 μs residence time), and exited into a vacuum chamber...
September 14, 2017: Journal of Physical Chemistry. A
Kenneth J Laszlo, Matthew F Bush
Collision cross section (Ω) values of gas-phase ions of proteins and protein complexes are used to probe the structures of the corresponding species in solution. Ions of many proteins exhibit increasing Ω values with increasing charge state, but most Ω values calculated for protein ions have used simple collision models that do not explicitly account for charge. Here we use a combination of ion mobility mass spectrometry experiments using helium gas and trajectory method calculations to characterize the extents to which increases in experimental Ω values with increasing charge state may be attributed to increased momentum transfer concomitant with enhanced long-range interactions between the protein ion and helium atoms...
September 14, 2017: Journal of Physical Chemistry. A
Javier Amaya Suárez, Jose J Plata, Antonio M Márquez, Javier Fernández Sanz
Quantum dots solar cells, QDSCs, are one of the candidates for being a reliable alternative to fossil fuels. However, the well-studied CdSe and CdTe-based QDSCs present a variety of issues for their use in consumer-goods applications. Silver sulfide, Ag2S, is a promising material, but poor efficiency has been reported for QDSCs based on this compound. The potential influence of each component of QDSCs is critical and key for the development of more efficient devices based on Ag2S. In this work, density functional theory calculations were performed to study the nature of the optoelectronic properties for an anatase-TiO2(101) surface sensitized with different silver sulfide nanoclusters...
September 14, 2017: Journal of Physical Chemistry. A
William W Parson
Rates of intramolecular electron transfer from a 1,1'-biphenylyl radical anion to six different acceptors on an androstane scaffold are examined with the aid of a theory that was developed recently to include effects of vibrational relaxations and dephasing. The electronic-interaction matrix element and other parameters needed for the theory are obtained by quantum-mechanical/molecular-mechanical simulations of the reactions in five solvents ranging from iso-octane to methyltetrahydrofuran. Intramolecular vibrational modes that are coupled to electron transfer are resolved in simulations in iso-octane and cyclohexane...
September 14, 2017: Journal of Physical Chemistry. A
Holger S P Müller, Oliver Zingsheim, Nadine Wehres, Jens-Uwe Grabow, Frank Lewen, Stephan Schlemmer
Isopropyl cyanide was recently detected in space as the first branched alkyl compound. Its abundance with respect to n-propyl cyanide in the Galactic center source Sagittarius B2(N2) is about 0.4. Astrochemical model calculations suggest that for the heavier homologue butyl cyanide the branched isomers dominate over the unbranched n-butyl cyanide and that 2-cyanobutane is the most abundant isomer. We have studied the rotational spectrum of 2-cyanobutane between 2 and 24 GHz using Fourier transform microwave spectroscopy and between 36 and 402 GHz employing (sub)millimeter absorption spectroscopy...
September 14, 2017: Journal of Physical Chemistry. A
Philip Patrick Anthony Malley, Jarod Nathaniel Grossman, Tara F Kahan
We have measured photolysis kinetics of the PAH anthracene in aqueous solution, in bulk ice, and at ice surfaces in the presence and absence of chromophoric dissolved organic matter (CDOM). Self-association, which occurs readily at ice surfaces, may be responsible for the faster anthracene photolysis observed there. Photolysis rate constants in liquid water increased significantly under conditions where significant anthracene self-association was observed. Concomitantly, kinetics changed from first order to second order, indicating that the photolysis mechanism at ice surfaces might be different than that in aqueous solution...
September 13, 2017: Journal of Physical Chemistry. A
Juan Carlos Gomez Martin, Claire Seaton, Marcelo Pessoa De Miranda, John Maurice Campbell Plane
We report the first direct kinetic study of the gas-phase reaction NaOH + H → Na + H2O, which is central to the chemistry of sodium in the upper atmosphere and in flames. The reaction was studied in a fast flow tube where NaOH was observed by multi-photon ionization and time-of-flight mass spectrometry, yielding k(NaOH + H, 230 - 298 K) = (3.8 ± 0.8)  10-11 cm3 molecule -1 s-1 (at 2σ confidence level), showing no significant temperature dependence over the indicated temperature range and essentially in agreement with previous estimates of the rate constant in hydrogen-rich flames...
September 13, 2017: Journal of Physical Chemistry. A
Benoît Champagne, Vincent Liégeois, Joseph G Fripiat, Frank E Harris
Restricted Hartree-Fock computations are reported for a methyl isocyanide polymer (repeating unit -C=N-CH$_3$), whose most stable conformation is expected to be a helical chain. The computations used a standard contracted Gaussian orbital set at the computational levels STO-3G, 3-21G, 6-31G, and 6-31G$^{**}$, and studies were made for two line-group configurations motivated by earlier work and by studies of space-filling molecular models: (1) A structure of line-group symmetry $L9_5$, containing a 9-fold screw axis with atoms displaced in the axial direction by 5/9 times the lattice constant, and (2) A structure of symmetry $L4_1$ that had been proposed, containing a four-fold screw axis with translation by 1/4 of the lattice constant...
September 13, 2017: Journal of Physical Chemistry. A
Gutto Raffyson Silva de Freitas, Sara E Coelho, Norberto K V Monteiro, Jannyely Moreira Neri, Livia Nunes Cavalcanti, Josiel B Domingos, Davi S Vieira, Miguel A F de Souza, Fabrício G Menezes
The acidity of organic compounds is highly relevant to understanding several biological processes. Although the relevance and challenges in estimating pKa values of organic acids is recognized by several reported works in the literature, there is a lack in determining the acidity of amides. This paper presents an experimental/theoretical combined investigation on the acid dissociation of the compound 6,7-dinitro-1,4-dihydro-quinoxaline-2,3-dione (DNQX), a well-established antagonist of ionotropic glutamate receptor GluA2...
September 13, 2017: Journal of Physical Chemistry. A
Chiara Giorio, Anne Monod, Lola Brégonzio-Rozier, Helen Langley DeWitt, Mathieu Cazaunau, Brice Temime-Roussel, Aline Gratien, Vincent Michoud, Edouard Pangui, Sylvain Ravier, Arthur T Zielinski, Andrea Tapparo, Reinhilde Vermeylen, Magda Claeys, Didier Voisin, Markus Kalberer, Jean-Francois Doussin
Aerosol-cloud interaction contributes to the largest uncertainties in the estimation and interpretation of the Earth's changing energy budget. The present study explores experimentally the impacts of water condensation evaporation events, mimicking processes occurring in atmospheric clouds, on the molecular composition of secondary organic aerosol (SOA) from the photooxidation of methacrolein. A range of on- and off-line mass spectrometry techniques were used to obtain a detailed chemical characterization of SOA formed in control experiments in dry conditions, in triphasic experiments, i...
September 13, 2017: Journal of Physical Chemistry. A
Soichi Ito, Takanori Nagami, Masayoshi Nakano
No abstract text is available yet for this article.
September 13, 2017: Journal of Physical Chemistry. A
Olga Grigorevna Khvostenko, Renat Ramilevich Kinzyabulatov, Laysan Zavzyatovna Khatymova, Evgeniy Evgen'evich Tseplin
This study was undertaken to find the previously unknown lowest triplet of the isolated molecule of tetracyanoquinodimethane (TCNQ), which is a widely used organic semiconductor. The problem is topical because the triplet excitation of this compound is involved in some processes which occur in electronic devices incorporating TCNQ and its derivatives, and information on the TCNQ triplet is needed for better understanding of these processes. The lowest triplet of TCNQ was obtained at 1.96 eV using UV/vis absorption spectroscopy with Br-containing solvents...
September 13, 2017: Journal of Physical Chemistry. A
Angela Hanna, Joshua Blechle, Ellen R Fisher
Understanding energy distributions and kinetic processes in NxOy plasma systems is vital to realizing their potential in a range of applications, including pollution abatement. Energy partitioning between degrees of freedom and multiple molecules formed within NxOy plasma systems (N2, N2O, N2/O2) was investigated using both optical emission and broadband absorption spec-troscopies. Specifically, we have determined electron temperatures (Te), as well as rotational (TR) and vibrational (TV) temperatures for various N2 (B(3)Πg and C(3)Πu) and NO (X(2)Π and A(2) Σ(+)) states...
September 13, 2017: Journal of Physical Chemistry. A
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