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Journal of Physical Chemistry. A

Steve Alexandre Ndengue, Richard Dawes, Fabien Gatti, Hua Guo
We examine the excitation of carbon monoxide from its rovibrational ground state via collisions with a hydrogen atom. Calculations employ the Multi-Configuration Time-Dependent Hartree method and treat the nonadiabatic dynamics with the inclusion of both the ground and the Renner-Teller coupled first excited electronic states. For this purpose, a new set of recently presented global HCO Potential Energy Surfaces (PESs) which cover the 0-3 eV range of energy are used. The results obtained here considering only the ground state (without the Renner-Teller coupling) are in qualitative agreement with those available in the literature...
July 13, 2018: Journal of Physical Chemistry. A
Yao Shen, Yu-Lin Zhao
Gentile statistics, which is famous for its advantages in dealing with composite particle systems, is a kind of fractional statistics. These years, researchers are concentrating on finding real systems that obey Gentile statistics. Five years ago, we discovered that the cyclic hydrocarbon polyenes called N-annulenes in Hückel model had certain correspondence with Gentile oscillators. According to their rotation and dihedral symmetry, these two systems had the same energy levels and partition functions. In this paper, we discuss the specific details of this correspondence...
July 13, 2018: Journal of Physical Chemistry. A
Kelly S Wilson, Cathy Y Wong
The exciton dynamics of pseudoisocyanine (PIC) is reported during the formation of a thin film dropcast from solution. Tilted pump pulses are used to spatially encode a pump-probe time delay, enabling the collection of a transient in a single shot. We demonstrate that a spatially encoded delay can be used to accurately measure exciton dynamics in thin-film samples, with a signal-to-noise ratio above 20 attained in 2 s. We report in situ linear absorption, fluorescence, and transient absorption measurements during the molecular aggregation of PIC...
July 12, 2018: Journal of Physical Chemistry. A
Van Tan Tran, Quoc Tri Tran
Density functional theory and multiconfigurational CASPT2 and RASPT2 methods are employed to investigate the low-lying states of CoGen-/0 (n = 1-3) clusters. With the RASPT2 approach, the active space is extended to 14 orbitals for CoGe-/0, 17 orbitals for CoGe2-/0, and 20 orbitals for CoGe3-/0. These active spaces include the 3d, 4s, and 4d of Co and 4p of Ge. The 4d of Co is incorporated into these active spaces in order to account for the important double-shell effect of Co. The structural parameters, vibrational frequencies, and relative energies of the low-lying states of CoGen-/0 (n = 1-3) are reported...
July 12, 2018: Journal of Physical Chemistry. A
Sha-Sha Xia, Alexis J Eugene, Marcelo I Guzman
Aerosols of variable composition, size, and shape are associated with public health concerns as well as with light-particle interactions that play a role in the energy balance of the atmosphere. Photochemical reactions of 2-oxocarboxylic acids in the aqueous phase are now known to contribute to the total secondary organic aerosol (SOA) budget. This work explores the cross reaction of glyoxylic (GA) and pyruvic (PA) acids in water, the two most abundant 2-oxocarboxylic acids in the atmosphere, under solar irradiation and dark thermal aging steps...
July 12, 2018: Journal of Physical Chemistry. A
Aniruddh Vashisth, Chowdhury Ashraf, Weiwei Zhang, Charles E Bakis, Adri C T van Duin
Various methods have been developed to perform atomistic-scale simulations for the cross-linking of polymers. Most of these methods involve connecting the reactive sites of the monomers, but these typically do not capture the complete reaction process from the reactants to final products through transition states. Experimental time-scales for cross-linking reactions in polymers range from minutes to hours - which are time-scales that are inaccessible to atomistic-scale simulations. Since simulating reactions on realistic time scales is computationally expensive, in this investigation, an accelerated simulation method was developed within the ReaxFF reactive force field framework...
July 11, 2018: Journal of Physical Chemistry. A
Liezel Labrador Estrella, Mannix Padayhag Balanay, Dong Hee Kim
This paper reports new D-D-π-A dyes based on N-annulated perylene, emphasizing on the enhanced dye-to-semiconductor charge transfer mechanism. A series of DFT calculations for new tPA-perylene-based dyes was conducted, starting from the systematic selection of DFT methods by reproducing the experimentally obtained properties of known perylene-based sensitizers. Accordingly, using the LC- ωPBE xc functional with 6-31+G(d) basis set for the time-dependent calculations of the excitation energies, a damping parameter of ω=0...
July 11, 2018: Journal of Physical Chemistry. A
Etienne Garand
IIn this paper, applications of cryogenic ion traps for forming reaction intermediates and solvated clusters from precursor ions generated by electrospray ionization are presented and discussed. These studies are motivated by the aim of spectroscopically probing isolated complexes that exhibit higher levels of complexity in chemical compositions and intermolecular interactions, which make them more closely resemble the systems existing in real-world environments. Illustrative examples are provided to highlight the current capabilities, showcase the detailed information available in the spectroscopic results, and outline general future directions...
July 11, 2018: Journal of Physical Chemistry. A
Kevin M Roenitz, Brian M Hays, Carson Powers, Morgan N McCabe, Houston Smith, Susanna L Widicus Weaver, Steven T Shipman
Microwave-millimeter/submillimeter wave double resonance spectroscopy has been developed with the use of technology typically employed in chirped-pulse Fourier transform microwave spectroscopy and fast-sweep direct absorption (sub)millimeter-wave spectroscopy. This technique offers the high sensitivity provided by millimeter/submillimeter fast-sweep techniques with the rapid data acquisition offered by chirped-pulse Fourier transform microwave spectrometers. Rather than detecting the movement of population as is observed in a traditional double resonance experiment, instead we detected the splitting of spectral lines arising from the AC Stark effect...
July 11, 2018: Journal of Physical Chemistry. A
Hannah M Allen, John D Crounse, Kelvin H Bates, Alexander Pai-Chung Teng, Mitchell P Krawiec-Thayer, Jean C Rivera-Rios, Frank N Keutsch, Jason M St Clair, Thomas F Hanisco, Kristian H Møller, Henrik Grum Kjaergaard, Paul O Wennberg
Hydroxymethyl hydroperoxide (HMHP), formed in the reaction of the \ce{C1} Criegee intermediate with water, is among the most abundant organic peroxides in the atmosphere. Although reaction with OH is thought to represent one of the most important atmospheric removal processes for HMHP, this reaction has been largely unexplored. In this study, we present laboratory measurements of the kinetics and products formed in the reaction of HMHP with OH. HMHP was oxidized by OH in an environmental chamber; the decay of the hydroperoxide and the formation of formic acid and formaldehyde were monitored over time using CF$_3$O$^-$ chemical ionization mass spectrometry (CIMS) and laser induced fluorescence (LIF)...
July 11, 2018: Journal of Physical Chemistry. A
Weiwei Yang, Qingxin Ma, Yongchun Liu, Jinzhu Ma, Biwu Chu, Ling Wang, Hong He
In this work, a relationship between the role of NH3 and the properties of mineral oxides (α-Fe2 O3 , α-Al2 O3 , CaO and MgO) in the evolution of NO3 - , SO4 2- and NH4 + has been established. It was found that the promotion effect of NH3 was more favorable for the formation of NO3 - (or SO4 2- ) and NH4 + on acidic α-Fe2 O3 and α-Al2 O3 due to acid-base interactions between NO2 with NH3 or between SO2 and NH3 , while this effect was weaker on basic CaO and MgO possibly due to their basic nature. The acid-base interaction (NO2 /SO2 with NH3 ) overpowered the redox reaction (SO2 with NO2 ) on Fe2 O3 owing to its unique redox chemistry...
July 11, 2018: Journal of Physical Chemistry. A
Junting Qiu, Shinnosuke Ishizuka, Kenichi Tonokura, Shinichi Enami
Secondary organic aerosol (SOA) found in polluted megacities contains benzoic acid (BA) as a major organic acid in addition to a variety of species including alkenes. In polluted air, ozone could be a major oxidizer for SOA, that induces subsequent reactions involving Criegee intermediates (CIs, carbonyl oxide RR'C∙-O-O∙/RR'C=O+-O-) formed by the -C=C- + O3 reaction at the gas/liquid interface. The possibility that abundant BA could be an effective scavenger of CIs at the interface remains to be investigated by direct experiments...
July 10, 2018: Journal of Physical Chemistry. A
Michael J Colaneri, Jacqueline Vitali
Electron Spin-Echo Envelope Modulation (ESEEM) signals attributed to axial water bound to Cu+2 have been detected and analyzed in Cu(II)-doped 17 O-water enriched potassium zinc sulfate hexahydrate (tutton salt) crystals. The magnetic field orientation dependences of low frequency modulations were measured to fit hyperfine and quadrupole coupling tensors of a 17 O (I=5/2) nucleus. The hyperfine tensor (Axx , Ayy , Azz : 0.13, 0.23, -3.81 MHz) exhibits almost axial symmetry with the largest value directed normal to the metal equatorial plane in the host structure...
July 10, 2018: Journal of Physical Chemistry. A
Johannes T Margraf, Karsten Reuter
Calculating the electronic structure of molecules and solids has become an important pillar of modern research in diverse fields of research from biology and materials science to chemistry and physics. Unfortunately, increasingly accurate and thus reliable approximate solution schemes to the underlying Schrödinger equation scale steeply in computational cost, rendering most accurate approaches like "gold standard" coupled cluster theory, CC, quickly intractable for larger systems of interest. Here we show that this scaling can be significantly reduced by applying machine-learning to the CC correlation energy...
July 9, 2018: Journal of Physical Chemistry. A
Dale Green, Franco Valduga de Almeida Camargo, Ismael A Heisler, Arend G Dijkstra, Garth A Jones
Two-dimensional optical spectroscopy is a powerful technique for the probing of coherent quantum superpositions. Recently, the finite width of the laser spectrum has been employed to selectively tune experiments for the study of particular coherences. This involves the exclusion of certain transition frequencies, which results in the elimination of specific Liouville pathways. The rigorous analysis of such experiments requires the use of ever more sophisticated theoretical models for the optical spectroscopy of electronic and vibronic systems...
July 9, 2018: Journal of Physical Chemistry. A
Samah Y Mohamed, Alexander Cory Davis, Mariam J Al Rashidi, S Mani Sarathy
Hydroperoxyalkylperoxy (OOQOOH) radicals are important intermediates in combustion chemistry. The conventional isomerization of OOQOOH radicals to form ketohydroperoxides has been long believed to be the most important chain branching reaction under the low temperature combustion conditions. In this work the kinetics of competing pathways (alternative isomerization, concerted elimination and H-exchange pathways) to the conventional isomerization of different β-, γ- and Δ- OOQOOH butane isomers are investigated...
July 8, 2018: Journal of Physical Chemistry. A
Oren Gajst, Luís Pinto da Silva, Joaquim C G Esteves da Silva, Dan Huppert
Steady-state and time-resolved fluorescence techniques were used to study the excited-state proton transfer (ESPT) to water of the reversible photoacid 2-naphthol-8-sulfonate (2N8S) in acetonitrile/water mixtures. In acetonitrile-rich mixtures, up to χwater ≤0.12, we found a slow ESPT process on the order of nanoseconds. At χwater ≈0.15, the RO- fluorescence band intensity is at minimum, whereas at χwater ≈0.030, it is at the maximum. The steady-state fluorescence spectra of these mixtures show that the intensity of the RO- fluorescence band at χwater ≈0...
July 6, 2018: Journal of Physical Chemistry. A
Guanyu Zhang, Ning Zhao, Petia Bobadova-Parvanova, Maodie Wang, Frank R Fronczek, Kevin Malcolm Smith, M Graça Henriques Vicente
A series of E-, Z-ethenyl- and ethynyl-linked BODIPY dimers were synthesized in 23-34% yields by condensation of pyrroles with the corresponding bis-benzaldehydes, followed by oxidation and boron complexation. The BODIPY dimers were characterized by 1H-, 13C, and 11B NMR spectroscopy, HRMS and, in the cases of 1b, 2 and 3, by X-ray crystallography. The spectroscopic properties for this series of dimers were investigated in THF solutions, and very similar absorption and emission profiles were observed for all dimers...
July 4, 2018: Journal of Physical Chemistry. A
Sergey S Lobanov, John A Daly, Alexander F Goncharov, Xiaojun Chan, Sanjit K Ghose, Hui Zhong, Lars Ehm, Taejin Kim, John B Parise
Capture of highly-volatile radioactive iodine is a promising application of metal organic frameworks (MOFs), thanks to their high porosity with flexible chemical architecture. Specifically, strong charge-transfer binding of iodine to the framework enables efficient and selective iodine uptake as well as its long-term storage. As such, precise knowledge of the electronic structure of iodine is essential for a detailed modelling of the iodine sorption process, which will allow for rational design of iodophilic MOFs in the future...
July 3, 2018: Journal of Physical Chemistry. A
Bikramaditya Mandal, Alexander Semenov, Dmitri A Babikov
It is shown that the mixed quantum/classical theory (MQCT) for the description of molecular scattering is considerably improved by using integer values of orbital angular momentum l, just like in quantum theory, instead of treating it as a continuous classical variable related to the impact parameter. This conclusion is justified by the excellent accuracy of the modified theory for prediction of the differential cross sections, at various values of collision energy and in both forward and backward scattering regimes...
July 3, 2018: Journal of Physical Chemistry. A
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