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  • Effects of Al2O3 atomic layer deposition on interfacial structure and electron transfer dynamics at Re-bipyridyl complex/TiO2 interfaces
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-03
    Jia Song, Aimin Ge, Brandon Piercy, Mark D. Losego, Tianquan Lian

    Atomic layer deposition (ALD) of oxide layers on sensitizer- and/or catalyst-functionalized semiconductor surfaces have been used to improve the stability of dye-sensitized solar cells and photoelectrosynthesis cells. However, how the ALD layer affects the interfacial structure of adsorbed molecules and interfacial electron transfer dynamics is still unclear. Herein, we investigated the effects of ALD of Al2O3 on adsorption structure of Re bipyridyl complex on TiO2 nanocrystalline films and rutile (0 0 1) single crystals by IR absorption and sum frequency generation spectroscopy. Further, the electron transfer dynamics between the Re complex and TiO2 film was also examined by ultrafast infrared transient absorption spectroscopy. Our results show that the electron injection yield decreases with the increase of ALD layer thickness.

    更新日期:2018-07-14
  • The protonated water trimer and its giant Fermi resonances
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-03
    Nagaprasad Reddy Samala, Noam Agmon

    The protonated water trimer is a prototype “proton wire” that can transport two protons nearly concertedly. This “proton transfer mode” (PTM) is an important contributor to the infrared spectrum of the isolated gas-phase cluster. We have simulated its infrared spectrum for both the hydrated and deuterated isotopologues, using vibrational 2nd order perturbation theory (VPT2) and ab initio molecular dynamics (AIMD) trajectories. VPT2 calculations explain quantitatively the experimental spectra at both high and low frequencies, provided that high-level quantum chemistry is utilized. In the D2-tagged hydrated cluster, the PTM undergoes giant Fermi resonances (FR’s) with two combination bands. In the deuterated analogue, one observes a single FR of “normal” intensity, manifested as the doublet recently reported experimentally. We provide band assignment for both isotopologues, with and without the D2 tag applied in experiment. We discuss possible manifestations of the giant resonance on proton transfer through water wires.

    更新日期:2018-07-14
  • Quantitative and sensitive mapping of imidacloprid on plants using multiphoton electron extraction spectroscopy
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-04
    Anneli Kruve, Valery Bulatov, Israel Schechter

    Neonicotinoids, including imidacloprid, are extensively used for plant protection against insects. Unfortunately, these effective pesticides are one of the reasons for the decline of the bee population in recent decades. Ensuring application of minimal pesticide quantity and preventing excess requires a fast method for monitoring the coverage on plants. We present a new, method based on multiphoton electron extraction spectroscopy (MEES), for detecting, quantifying and mapping of imidacloprid coverage on plants. Imaging and quantitative analyses were demonstrated on several plant surfaces including olive and mint leaves and orange peel. Method provides both low detection limits (down to nanogram level) and good trueness. This method is fast and can be directly performed with no sample pre-treatment, thus, it is a good candidate for field analyses.

    更新日期:2018-07-14
  • Entropy-enthalpy compensation in conjugated proteins
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-12
    Lavi S. Bigman, Yaakov Levy

    Entropy–enthalpy compensation is observed in many reactions, particularly for polymeric biomolecules that often involve large changes in entropy and enthalpy. The imperfect cancelation of entropy and enthalpy dictates many biophysical characteristics, such as protein thermodynamic stability and the free energy barrier for protein folding. In this study, we examine how tethering a conjugate to a protein may affect the thermodynamic stability of the protein. We found that a conjugate mostly affects the unfolded state by eliminating formation of some residual interactions. Consequently, both the enthalpy and the entropy of the unfolded state are affected. We suggest that, because this effect is not localized, the gain in conformational flexibility (i.e., increased entropy) is larger than the loss of some residual interaction (i.e., increased enthalpy). Therefore, the unfolded state of the conjugated protein has a lower free energy than that of the free protein, resulting in thermodynamic destabilization.

    更新日期:2018-07-14
  • Lipid-induced dynamics of photoreceptors monitored by time-resolved step-scan FTIR spectroscopy
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-20
    Michael Jawurek, Jessica Dröden, Benedikt Peter, Clemens Glaubitz, Karin Hauser

    The lipid environment plays a crucial role for the function of membrane proteins. We analyzed the influence of various lipid properties on the photoreceptors Bacteriorhodopsin (BR) and Proteorhodopsin (PR) by time-resolved step-scan FTIR spectroscopy. The photoreceptors were reconstituted into liposomes thereby providing an uniform biomimetic membrane, and the physical properties of the lipids were systematically varied. The lipid phase alters significantly the protonation dynamics of both, BR and PR. We also analyzed the conformational changes of the photoreceptors during the proton pumping mechanism and could demonstrate that a lipid-induced altered protonation dynamics is correlated to an altered conformational dynamics. Our results indicate that the fluidity of the membrane environment directly influences the structural-functional correlation.

    更新日期:2018-07-14
  • A Quasi Quantum Treatment of the spin orbit state changing and conserving rotationally inelastic NO(X)-He collisions
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-22
    Xia Zhang, Steven Stolte

    A Quasi Quantum Treatment (QQT) of the rotational inelastic NO(X)-He collisions in the pure Hund’s case (a) spin orbit state conserving transitions is extended to the mixed Hund’s case (a) spin orbit state conserving and changing transitions. To enable this extension a polar and azimuthal angle dependent intermolecular hard-shell PES, VS(RS,γR,χR)=ES, has been developed. The DCSs and ICSs calculated by QQT are compared with those obtained from QM exact calculations onto a full R-range ab initio PES. The rotationally inelastic scattering of NO(X) from He presents a paradigm for the rotationally inelastic scattering at a thermal collision energy of molecules residing in a Π electronic rotational eigenstate.

    更新日期:2018-07-14
  • State-to-state quantum dynamics of the H + LiF → Li + HF reaction on an accurate ab initio potential energy surface
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-22
    Changjian Xie, Xinguo Liu, Hua Guo

    Quantum state-to-state dynamics calculations are reported for the H + LiF(vi, ji) → HF(vf, jf) + Li reaction on a recently reported ground state X̃2A′ potential energy surface. It was found that at low collision energies the title reaction is dominated by long-lived resonances, while the lifetimes of resonances become shorter at higher energies. The existence of resonances is also supported by the differential cross section, which has mostly forward and sideways bias. The integral cross section rises with collision energy slowly, and the opacity function suggests that the reaction is dominated by small impact parameter collisions. The HF product has cold vibrational state distributions in range of the collision energy studied here, although its rotational state distributions peak near the highest accessible rotational states. This early-barrier reaction shows some enhancement by translational energy, but internal excitations of the LiF reactant have more complex behaviors.

    更新日期:2018-07-14
  • A combined time-resolved infrared and density functional theory study of the lowest excited states of 9-fluorenone and 2-naphthaldehyde
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-24
    Magnus W.D. Hanson-Heine, James A. Calladine, Jixin Yang, Michael Towrie, Raphael Horvath, Nicholas A. Besley, Michael W. George

    A combined experimental and theoretical study of the infrared (IR) spectra of 2-naphthaldehyde and 9-fluorenone in their ground and first excited singlet and triplet electronic states is presented. IR studies have also been carried out using supercritical krypton (scKr) as a solvent to measure spectra in the ground and triplet excited states. This solvent provides a weakly interacting environment that is closer to the gas phase and allows a direct comparison with the calculated spectra for a single molecule. The IR spectra for the three different states are computed with Kohn-Sham density functional theory. For the first excited singlet state it is necessary to use an overlap procedure that allows the excited state to be studied by preventing variational collapse to the ground state. This allows the excited singlet state to be studied in an analogous approach to the ground and excited triplet state, in contrast to using time-dependent density functional theory. The good agreement between the calculated excited state spectra and the experiment provides insight into the nature of the excited states. For the ground and excited triplet state the anharmonic vibrational frequencies are computed using the transition optimized shifted Hermite method, and for these molecules the hybrid B97-1 functional is found to provide the closest agreement with experiment in the ground state.

    更新日期:2018-07-14
  • Exploring enhanced hydrogen adsorption on Ti doped Al nanoclusters: A DFT study
    Chem. Phys. (IF 1.707) Pub Date : 2018-04-27
    Bishwajit Boruah, Bulumoni Kalita

    The detailed mechanism of adsorption and dissociation of molecular hydrogen on bare and Ti doped Al6 clusters has been studied using Density Functional Theory (DFT). The study shows that the doping of Ti atom significantly changes the geometric and electronic structures of Al6 cluster. Noticeable electronic charge transfer takes place from Al to Ti atoms in TiAl5. The number of energy states near the Fermi level of bare Al6 cluster also increases upon Ti doping. Moreover, the weak molecular hydrogen physisorption on Al6 becomes relatively stronger in TiAl5 with binding energy value of −0.12 eV. Similarly, dissociative hydrogen chemisorption energy on TiAl5 (−2.80 eV) is higher than that on Al6 (−2.74 eV). The computed molecular hydrogen gravimetric content in TiAl5 cluster is 3.2 wt%. Further, dissociation of H2 in TiAl5 involves an activation barrier of 0.54 eV in contrast with barrier less dissociation in bare Al6 cluster.

    更新日期:2018-07-14
  • Thermal evaporated C60 modified by Pt as counter electrode for dye-sensitized solar cells
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-10
    Xiu De Yang, DeBei Liu, Yi Hu, Gang Wang, Guang Dong Zhou, Ping Li, Bo Wu, Qun Liang Song

    Almost all carbon-based materials as counter electrode (CE) for dye-sensitized solar cells (DSSCs) with good performance have been identified in previous studies. Unfortunately, the device with fullerene (C60) or its derivative on fluorine doped tin oxide (FTO) substrate prepared by spin-coating was not the case. Our experimental results show that the C60 fabricated by vacuum thermal deposition performs much better than that prepared by spin-coating though the fill factor(FF) and power conversion efficiency(PCE) are still poor. Further improvement has been achieved in this study by trace Pt modifying thermal deposited C60 CE with a device efficiency of 5.78%, comparable to the one with standard Pt CE. This composite CE was obtained by thermal decomposing a small amount of chloroplatinic acid hexahydrate on FTO prior to C60. The trace Pt underneath the C60 film is believed to improve the conductivity of the C60 CE and then the performance of DSSCs.

    更新日期:2018-07-12
  • Glutathione influence on the photoluminescence from semiconducting single-walled carbon nanotubes compared with other thiol compounds
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-09
    N.V. Kurnosov, V.S. Leontiev, V.A. Karachevtsev

    The influence of antioxidant glutathione (GSH) on the photoluminescence (PL) from the semiconducting single-walled carbon nanotubes (SWNTs) suspended with DNA in water has been studied in this research. The strong PL enhancement was found after GSH doping (10-6–10-4 M) of the nanotube suspension, which is explained by passivation of the emission-quenching defects on the nanotube sidewall by the reactive thiol group in the GSH structure. The PL increase depends on the sonication treatment of the nanotube suspension, the quantity of this increase also differs in the emission bands specified by the disordered biopolymer coverage of corresponding nanotubes. This observation allows the ratiometric PL detection of glutathione. The nanotube PL is less sensitive to GSH impact as compared to cysteine. Experiments with other thiol-containing compounds as dithiothreitol and dithioerythritol showed a tendency that the compound with lower redox potential causes a stronger increase of the PL from suspended SWNTs.

    更新日期:2018-07-10
  • The effect of laser pulse bandwidth on the measurement of the frequency fluctuation correlation functions in 2D electronic spectroscopy
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-01
    Paweł J. Nowakowski, M. Faisal Khyasudeen, Howe-Siang Tan

    Several methods have been proposed to obtain the frequency fluctuation correlation function (FFCF) of a transition from the 2DES spectra without complicated fitting procedures. Although all were shown to give correct values in idealized conditions, this might not be applicable in real experimental circumstances. Here, we observe the effects of using different bandwidth excitation pulses in three commonly used methods: ellipticity, center line slope of slices along excitation (CLSω1) and detection (CLSω3) frequencies. The studies were performed on the Qy transition of chlorophyll a. We show that the CLSω3 method gives consistent results for all bandwidths used. For the other two methods, the recovered FFCF values decrease in magnitude with decreasing excitation pulse bandwidths. We also show that by applying the simplified expressions derived by Do et al., incorporating finite pulses in 2DES spectra simulation, we can recover accurate FFCFs using any of these methods.

    更新日期:2018-07-03
  • Adsorption of CH3I on Ag(111) and Ag2O(111) surface: A density functional theory study
    Chem. Phys. (IF 1.707) Pub Date : 2018-07-02
    Lin Yang, YaoLin Zhao, Kui Li, ZhongCun Chen, Peng Zhang, WeiQun Shi

    First-principles density functional study has been performed to systematically investigate the adsorption of CH3I on Ag(111) and Ag2O(111) surfaces at different coverages. It is found that the adsorption energy of CH3I on two surfaces at all sites is coverage-dependent, and the adsorption is thermodynamic favorable. The interaction between CH3I and two surfaces can be mainly attributed to the hybridization of I(p) state and Ag(d) state. For the adsorption of CH3I on Ag(111) surface, fcc site is the most stable site whether at lower or higher coverage. For Ag2O(111) surface, AgCUS site and AgCUS(AgCSA) site is more favorable at lower and higher coverage, respectively. The large adsorption energy occurred on the adsorption of CH3I on AgCUS(AgCSA) site is due to the strong interaction between I atom and AgCUS atom and the formation of H-O bond according to the LDOS and CDD calculations.

    更新日期:2018-07-03
  • Friction coefficient between a hydrophobic soft solid surface and a fluid: determined by QCM-D
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-30
    Rosalba Patiño-Herrera, R. Catarino-Centeno, Armando Gama Goicochea, Marissa Robles-Martínez, Ramiro Rico Martínez, Elías Pérez
    更新日期:2018-07-01
  • Re-evaluation of the century-old Langmuir isotherm for modeling adsorption phenomena in solution
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-28
    Saeid Azizian, Setareh Eris, Lee D. Wilson
    更新日期:2018-06-30
  • 1H and 17O NMR study of H-bond dynamics in picolinic acid N-oxide solutions in acetonitrile-h3 and acetonitrile-d3: novel aspects of old casus
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-27
    Arūnas Maršalka, Laurynas Dagys, Virginija Jakubkienė, Sigitas Tumkevičius, Vytautas Balevicius
    更新日期:2018-06-28
  • Mechanistic and kinetic study on the reaction of Pyrrole (C4H5N) with O(3P)
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-27
    Yunju Zhang, Ruojing Song, Yuxi Sun, Jingyu Sun, Yizhen Tang, Rongshun Wang

    The mechanism and kinetic for the reaction of Pyrrole + O(3P) has been investigated using CCSD(T)/cc-pVDZ//M06-2X/6-311++G(d,p) method in combine with multichannel RRKM-TST calculation. The title reaction included three manners, namely, α-C-addition, β-C-addition, and direct H-abstraction. The rate constants and branching ratios for nine product channels are calculated. It is predicted that the total rate coefficients vary with temperature, and exhibit strong positive temperature dependence. The stabilization of IM1 dominated the reaction at T≤ 350 K; the formation of P1 + H by H-elimination from IM1 is dominant at higher temperature. Moreover, the total rate coefficients are not affected by pressure.

    更新日期:2018-06-28
  • Gas sensing behavior of Metal-Phthalocyanines: Effects of electronic structure on sensitivity
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-27
    Malay Kumar Rana, Mousumi Sinha, Siddhartha Panda

    Cu-phthalocyanine (CuPc) and five of its metal variants (M = Mg, Mn, Co, Ni, and Zn) have been studied by density functional theory (DFT) methods for sensing five volatile organic compounds – isoprene, acetone, ammonia, methanol, and methane. Having performed experimental validation of the methods, interaction energies, binding configurations, changes in charge distributions and energy levels after interaction, and interaction barriers were studied to account for the sensitivity trend across the analytes for CuPc, while also providing supporting data from experiments carried out herein. It is also demonstrated that relatively simple calculations of interaction barrier can result in quick screening of metal-Pc variants for an analyte without any extensive experimental or computational efforts. Present literature lacks such detailed studies for these materials and analytes. Thus, this work would consolidate the understanding of sensing phenomena at the electronic structure level that could be useful for emerging technologies in gas sensing.

    更新日期:2018-06-28
  • Solvation Effects Alter the Photochemistry of 2-Thiocytosine
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-27
    Mikołaj J. Janicki, Rafał Szabla, Jiří Šponer, Robert W. Góa

    Radiationless deactivation channels of 2-thiocytosine in aqueous environment are revisited by means of quantum-chemical simulations of excited-state absorption spectra, and investigations of potential energy surfaces of the chromophore clustered with two water molecules using the algebraic diagrammatic construction method to the second-order (ADC(2)), and multireference configuration interaction with single and double excitations (MR-CISD) methods. We argue that interactions of explicit water molecules with thiocarbonyl group might enable water-chromophore electron transfer (WCET) which leads to formation of intersystem crossing that was not considered previously. This is the first example of a WCET process occurring in the triplet manifold of electronic states. This phenomenon might explain nonradiative decay of the triplet state population observed in thiopyrimidines in the absence of molecular oxygen. According to our calculations this WCET process might also entail a subsequent, virtually barrierless, electron-driven proton transfer (EDPT) resulting in the formation of hydroxyl radical which could further participate in photohydration or deamination reactions.

    更新日期:2018-06-28
  • Coupled rate-equation hydrodynamic simulation of a Rydberg gas Gaussian ellipsoid: Classical avalanche and evolution to molecular plasma
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-25
    Rafael Haenel, Edward Grant

    An ellipsoidal volume of Rydberg molecules, entrained in a supersonic molecular beam, evolves on a nanosecond timescale to form a strongly coupled ultracold plasma. We present coupled rate-equation simulations that model the underlying kinetic processes and molecular dissociation channels in both a uniformly distributed plasma and under the conditions dictated by our experimental geometry. Simulations predict a fast electron-driven collisional avalanche to plasma followed by slow electron-ion recombination. Within 20 μμs, release of Rydberg binding energy raises the electron temperature of a static plasma to Te=100Te=100 K. Providing for a quasi-self-similar expansion, the hot electron gas drives ion radial motion, reducing TeTe. These simulations provide a classical baseline model from which to consider quantum effects in the evolution of charge gradients and ambipolar forces in an experimental system undergoing responsive avalanche dynamics.

    更新日期:2018-06-27
  • Vibronic coupling model to calculate the photoelectron spectrum of phenol
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-26
    M.P. Taylor, G.A. Worth
    更新日期:2018-06-27
  • Initial stage of C60 cation formation in superacids
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-22
    G. Pillet, D. Tristant, M. Berd, W. Bacsa, P. Puech

    While superacids are solvents for individualizing carbon nanotubes, the behavior of insulating C60 is different. The final ionization state depends on the superacid used. With chlorosulfonic acid, chlorination is observed while with fuming sulfuric acid, sulfonation has been reported. Both reactions are fast and it is important to characterize the first step to understand the involved reaction mechanisms. Employing Raman spectroscopy and first-principles calculations, we show that C60+ is present with chlorosulfonic acid and surprisingly C602+ ions are predominantly formed during the first seconds after immersion in fuming sulfuric acid.

    更新日期:2018-06-22
  • From natural biomaterials to environment-friendly and sustainable nonvolatile memory device
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-22
    Xiaojun Wang, Shu Tian, Bai Sun, Xiaoxia Li, Bolin Guo, Yushuang Zeng, Bing Li, Weiting Luo
    更新日期:2018-06-22
  • Chemical identification of the amyloid peptide aggregation-prone Al(III)-peptide complexes by resonance Raman signatures: A computational study
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-19
    Baoling Tian, Changhang Cheng, Tongtao Yue, Na Lin, Hao Ren

    The aggregation of amyloid peptides as fibril-like β-sheet conformers is of vital importance in the development of Alzheimer’s disease. It has been experimentally shown that Al(III) ions are aggregation-prone for amyloid peptides. Recently, it was proposed that Al(III) can directly bond to the peptide backbone and forming a ring structure. This ring structure drastically alters the secondary structure of the amyloid fibrils and induces irreversible denaturation. However, the kinetics and dynamics of Al(III)-peptide binding is still not well understood, which requires the detailed knowledge of the geometric and electronic structures of the binding intermediates and the products. In the present work, based on simple molecular models, we performed ab initio calculations for the spontaneous resonance Raman (RR) spectroscopic signals. The Raman characteristics of the complexes are distinct enough for chemical identification. All these features can be related to the vibronic coupling between the vibrational fingerprints and the specific electronic transitions. The rich structural information contained in the RR signals enables us to identify and characterize the Al(III)-peptide complexes at low concentrations typically in life sciences.

    更新日期:2018-06-20
  • Vibrationally resolved absorption and fluorescence spectra of perylene and N-substituted derivatives from autocorrelation function approaches
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-19
    Tao Xiong, Radosław Włodarczyk, Peter Saalfrank

    Vibrationally resolved absorption and emission (fluorescence) spectra of perylene and its N-derivatives in gas phase and in solution (acetonitrile) were simulated using a time-dependent approach based on correlation functions determined by density functional theory. By systematically varying the number and position of N atoms, it is shown that the presence of nitrogen heteroatoms has a negligible effect on the molecular structure and geometric distortions upon electronic transitions, while spectral properties change: in particular the number of N atoms is important while their position is less decisive. Thus, the N-substitution can be used to fine-tune the optical properties of perylene-based molecules.

    更新日期:2018-06-20
  • Herman-Kluk propagator is free from zero-point energy leakage
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-18
    Max Buchholz, Erika Fallacara, Fabian Gottwald, Michele Ceotto, Frank Grossmann, Sergei D. Ivanov

    Quasiclassical techniques constitute a promising route to approximate quantum dynamics based on classical trajectories starting from a quantum-mechanically correct distribution. One of their main drawbacks is the so-called zero-point energy (ZPE) leakage, that is artificial redistribution of energy from the modes with high frequency and thus high ZPE to those with low frequency and ZPE due to classical equipartition. Here, we show that the elaborate semiclassical formalism based on the Herman-Kluk propagator is free from the ZPE leakage despite utilizing purely classical propagation. We demonstrate this with example applications for two- and three-dimensional anharmonically coupled oscillators. This finding opens the road to correct dynamical simulations of systems with a multitude of degrees of freedom that cannot be treated fully quantum-mechanically due to the exponential increase of the numerical effort.

    更新日期:2018-06-19
  • Effect of Vibrational Pre-Excitation on Sub-Femtosecond Structural Evolution of Water Cation in 2A1 State
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-15
    B. Jayachander Rao, Minhaeng Cho

    We study the effects of vibrational excitation of neutral water molecule on sub-femtosecond nuclear dynamics of the 2A1 electronic state of cationic water and its isotopomers that are induced by high-harmonic generation (HHG) process. Both the photoelectron spectra and the autocorrelation functions of electronically excited states of M2O+ (M = H, D, and T) that are produced by Franck-Condon ionization of vibrationally pre-excited M2O to its 2A1 electronic state are calculated. HHG signals are also calculated from the square of the absolute value of autocorrelation functions. In addition, the ratio of the HHG signal of D2O+ to that of H2O+ and that between T2O+ and H2O+ are calculated with respect to time, for varying initially prepared vibrational state of the corresponding neutral molecule. Vibrational dynamics are notably strong on the 2A1 state of the cationic species, as the initial vibrational quantum number increases. The HHG signal of a heavier isotopomer is larger than that of water when the initial vibrational state is on its ground state. The expectation values of the bond length and bond angle show quasiperiodic oscillations with respect to time, which are ascribed to the observed overall rise in the HHG signals. Exceptionally strong vibrational dynamics observed on the 2A1 state potential energy surface of the cationic water molecule can be attributed to the excitation of water bending mode upon Franck-Condon ionization of the corresponding neutral molecule. Here, the observed peaks in the ratios of the HHG signals are theoretically explained in terms of time-evolving molecular structures at two different turning points of the 2A1 surface. We anticipate that the present computational method of solving time-dependent Schrödinger equation would be of use to provide explanations on both ultrafast and chiroptical HHG spectroscopy of polyatomic molecules with certain handedness.

    更新日期:2018-06-15
  • Theoretical Study of Charge-Transfer Processes at Finite Temperature using a novel Thermal Schrödinger Equation
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-15
    Raffaele Borrelli

    Quantum dynamics of electron transfer (ET) between redox pairs at finite temperature is described using an approach based on Thermo-Field Dynamics theory. This formulation treats temperature effects in the Hilbert space without introducing the Liouville space. The solution of Thermo-Field Dynamics equations with a novel technique for the propagation of Tensor Trains is implemented and discussed. The methodology is applied to the study of the electron-transfer process between the cofactors in the bacterial reaction center, and the results are compared with the second order cumulant approach, showing that the latter can reproduce both short- and long-time dynamics of the electron-transfer process.

    更新日期:2018-06-15
  • Ab Initio Photodynamics of Model EUV Photoresists
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-15
    Jan Chalabala, Ondřej Dvořák, tr Slavíček
    更新日期:2018-06-15
  • Improved Potential Energy Surfaces of Thioanisole and the Effect of Upper Surface Variations on the Product Distribution Upon Photodissociation ☆
    Chem. Phys. (IF 1.707) Pub Date : 2018-06-14
    Yinan Shu, Donald G. Truhlar

    Electronically nonadiabatic photodissociation can be investigated in detail by experiments. This provides an opportunity to validate the current theory of electronically nonadiabatic processes, but is great challenge because the time scale of photodissociation processes can be long compared to the current capability for accurate direct dynamics simulations. To circumvent this difficulty, we have been using analytic diabatic potential energy matrices, such that the simulation time scale can be extended to the nanosecond region without neglecting the effects of external electron correlation. In previous work, we have developed full-dimensional three-state potential energy matrices for thioanisole photodissociation. In the current work, we extend this work in two main ways: (i) we improve the treatment of the initial torsional potential, and (ii) we shift the potential energy surfaces to investigate the quantitative effect on the dissociation lifetimes and product branching ratios of changing the energy and location of the S1–S2 conical intersection.

    更新日期:2018-06-14
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  • Effect of oligomer length on vibrational coupling and energy relaxation in double-stranded DNA
    Chem. Phys. (IF 1.707) Pub Date : 2017-12-19
    Gordon Hithell, Paul M. Donaldson, Gregory M. Greetham, Michael Towrie, Anthony W. Parker, Glenn A. Burley, Neil T. Hunt
    更新日期:2018-06-14
  • Infrared insights into the effect of cholesterol on lipid membranes
    Chem. Phys. (IF 1.707) Pub Date : 2017-12-21
    P. Stevenson, A. Tokmakoff
    更新日期:2018-06-14
  • Photochemical dynamics of a trimethyl-phosphine derivatized [FeFe]-hydrogenase model compound
    Chem. Phys. (IF 1.707) Pub Date : 2017-12-23
    Rachel L. Meyer, Annette D. Zhandosova, Tara M. Biser, Edwin J. Heilweil, Christopher J. Stromberg

    Though there have been many studies on photosensitizers coupled to model complexes of the [FeFe]-hydrogenases, few have looked at how the models react upon exposure to light. To extract photoreaction information, ultrafast time-resolved UV/visible pump, IR probe spectroscopy was performed on Fe2(μ-S2C2H4)(CO)4(PMe3)2 (2b) dissolved in heptane and acetonitrile and the photochemical dynamics were determined. Excitation with 532 and 355 nm light produces bleaches and new absorptions that decay to half their original intensity with time constants of 300 ± 120 ps and 380 ± 210 ps in heptane and acetonitrile, respectively. These features persist to the microsecond timescale. The dynamics of 2b are assigned to formation of an initial set of photoproducts, which were a mixture of excited-state tricarbonyl isomers. These isomers decay into another set of long-lived photoproducts in which approximately half the excited-state tricarbonyl isomers recombine with CO to form another complex mixture of tricarbonyl and tetracarbonyl isomers.

    更新日期:2018-06-14
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  • Direct observation of the change in transient molecular structure of 9,9′-bianthryl using a 10 fs pulse UV laser
    Chem. Phys. (IF 1.707) Pub Date : 2017-12-28
    Sena Hashimoto, Atsushi Yabushita, Takayoshi Kobayashi, Kotaro Okamura, Izumi Iwakura
    更新日期:2018-06-14
  • Direct application of the phase estimation algorithm to find the eigenvalues of the Hamiltonians
    Chem. Phys. (IF 1.707) Pub Date : 2018-01-04
    Ammar Daskin, Sabre Kais

    The eigenvalue of a Hamiltonian, H , can be estimated through the phase estimation algorithm given the matrix exponential of the Hamiltonian, exp ( - i H ) . The difficulty of this exponentiation impedes the applications of the phase estimation algorithm particularly when H is composed of non-commuting terms. In this paper, we present a method to use the Hamiltonian matrix directly in the phase estimation algorithm by using an ancilla based framework: In this framework, we also show how to find the power of the Hamiltonian matrix-which is necessary in the phase estimation algorithm-through the successive applications. This may eliminate the necessity of matrix exponential for the phase estimation algorithm and therefore provide an efficient way to estimate the eigenvalues of particular Hamiltonians. The classical and quantum algorithmic complexities of the framework are analyzed for the Hamiltonians which can be written as a sum of simple unitary matrices and shown that a Hamiltonian of order 2 n written as a sum of L number of simple terms can be used in the phase estimation algorithm with ( n + 1 + logL ) number of qubits and O ( 2 a nL ) number of quantum operations, where a is the number of iterations in the phase estimation. In addition, we use the Hamiltonian of the hydrogen molecule as an example system and present the simulation results for finding its ground state energy.

    更新日期:2018-06-14
  • 更新日期:2018-06-05
  • 更新日期:2018-06-04
  • Impact of the range of the interaction on the quantum dynamics of a bosonic Josephson junction
    Chem. Phys. (IF 1.707) Pub Date : 2018-01-31
    Sudip Kumar Haldar, Ofir E. Alon

    The out-of-equilibrium quantum dynamics of a bosonic Josephson junction (BJJ) with long-range interaction is studied in real space by solving the time-dependent many-body Schrödinger equation numerically accurately using the multiconfigurational time-dependent Hartree method for bosons. Having the many-boson wave-function at hand we can examine the impact of the range of the interaction on the properties of the BJJ dynamics, viz. density oscillations and their collapse, self trapping, depletion and fragmentation, as well as the position variance, both at the mean-field and many-body level. Explicitly, the frequency of the density oscillations and the time required for their collapse, the value of fragmentation at the plateau, the maximal and the minimal values of the position variance in each cycle of oscillation and the overall pace of its growth are key to our study. We find competitive effect between the interaction and the confining trap. The presence of the tail part of the interaction basically enhances the effective repulsion as the range of the interaction is increased starting from a short, finite range. But, as the range becomes comparable with the trap size, the system approaches a situation where all the atoms feel a constant potential and the impact of the tail on the dynamics diminishes. There is an optimal range of the interaction in which physical quantities of the junction are attaining their extreme values.

    更新日期:2018-06-03
  • Time-dependent framework for energy and charge currents in nanoscale systems
    Chem. Phys. (IF 1.707) Pub Date : 2018-01-31
    Thomas Lehmann, Alexander Croy, Rafael Gutiérrez, Gianaurelio Cuniberti

    The calculation of time-dependent charge and energy currents in nanoscale systems is a challenging task. Nevertheless it is crucial for gaining a deep understanding of the relevant processes at the nanoscale. We extend the auxiliary-mode approach for time-dependent charge transport to allow for the calculation of energy currents for arbitrary time dependencies. We apply the approach to two illustrative examples, a single-level system and a benzene ring, demonstrating its usefulness for a wide range of problems beyond simple toy models, such as molecular devices.

    更新日期:2018-06-03
  • 更新日期:2018-06-03
  • Time-resolved infrared studies of the unfolding of a light triggered β-hairpin peptide
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-06
    Michael S. Rampp, Stefan M. Hofmann, Tom Podewin, Anja Hoffmann-Röder, Luis Moroder, Wolfgang Zinth

    The light triggered unfolding reaction of the azobenzene peptide AzoTrpZip2 is investigated from 1 ps to 100 µs. Absorption changes show that the unfolding is a multistep process with the initial breaking of the hydrogen bonds in the vicinity of the AMPP chromophore on the 1 ns time scale followed by the disappearance of the remaining interstrand hydrogen bonds of the native hairpin structure with a 1.9 µs process. Subsequently, the hydrophobic core structure still stabilising a hairpin-like pattern rearranges in a 17 µs process. The strong slowing down of this reaction at lower temperature points to a barrier height in the range of 60 kJ/mol.

    更新日期:2018-06-03
  • Structure of micelles and micro-emulsions probed through the molecular reorientation of water
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-07
    Eliane P. van Dam, Huib J. Bakker

    We study the structural properties of dodecyltrimethylammonium bromide (DTAB) micelles and micro-emulsions by probing the molecular reorientation of water with polarization-resolved infrared pump-probe spectroscopy. For all systems studied, we observe that a fraction of water reorients on a much slower timescale than bulk water. This slow water fraction increases sublinear with increasing DTAB concentration, indicating an increase of the micelle size and enhanced micelle aggregation with concentration. We observe that the addition of oil to the micelle solutions, leading to the formation of a micro-emulsion, does not lead to a significant change of the fraction of slow water, showing that the added oil molecules are well solvated within the core of the micelles, and thus completely shielded from water.

    更新日期:2018-06-03
  • Vibrational studies of saccharide-induced lipid film reorganization at aqueous/air interfaces
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-09
    Katie A. Link, Chia-Yun Hsieh, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang, Robert A. Walker
    更新日期:2018-06-03
  • Coherent dynamics in cavity femtochemistry: Application of the multi-configuration time-dependent Hartree method
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-12
    Oriol Vendrell

    The photochemistry of a molecular ensemble coupled to a resonance cavity and triggered by a femtosecond laser pulse is investigated from a real-time, quantum dynamics perspective with the multi-configuration time-dependent Hartree method. Coherent excitation of a superposition of electronic states in the ensemble leads to superradiant energy transfer to the cavity characterized by quadratic scaling with the number of molecules. Electronic decoherence associated with loss of nuclear wave packet overlap among those states destroys superradiant energy transfer, returning to a linear regime. For equal pump laser conditions, the photoexcitation probability per molecule decreases with increase of the number of molecules inside the cavity. This is caused by a loss of resonance condition of the laser with the bright electronic-photonic states of the coupled cavity-ensemble system. Increase of the laser bandwidth restores the energy transferred per molecule and the trigger probability remains independent of the number of molecules in the cavity.

    更新日期:2018-06-03
  • 更新日期:2018-06-03
  • Vibrational heavy atom effect controls relaxation and spectral diffusion in triphenyl hydride complexes
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-14
    Cynthia G. Pyles, Courtney M. Olson, Aaron M. Massari

    A series of three triphenyl hydride compounds was investigated in a range of solvents by Fourier transform infrared (FTIR), IR pump-probe, and two-dimensional IR (2D-IR) spectroscopies. The mass of the central atom of the three compounds was varied systematically down the group 14 elements of silicon, germanium, and tin. FTIR studies provided evidence that the solvent perturbs the three hydride modes in a similar manner, as indicated by identical solvatochromic and broadening trends. IR pump-probe measurements showed that the vibrational lifetime of the hydride stretch increased when the mass of the central atom increased. Density functional theory calculations asserted that the vibrational modes of the three compounds are nearly identical except for the hydride stretching and wagging modes. Interestingly, frequency-frequency correlation functions obtained from 2D-IR spectra indicated that an increasingly large central atom produces small, but measurable changes in the dynamics of the solvation shell surrounding each compound.

    更新日期:2018-06-03
  • Variance of an anisotropic Bose-Einstein condensate
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-16
    Shachar Klaiman, Raphael Beinke, Lorenz S. Cederbaum, Alexej I. Streltsov, Ofir E. Alon
    更新日期:2018-06-03
  • Supersonic beams of mixed gases: A method for studying cold collisions
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-19
    William E. Perreault, Nandini Mukherjee, Richard N. Zare

    We show that collisions in a single supersonic molecular beam reach characteristic temperatures in the range of a few Kelvin. Experiments have been carried out for mixtures of H2 and HD as well as HD and D2 in a pulsed supersonic expansion. From the measured time-of-flight spectrum, we find that the high velocity edge of the distribution for both species is nearly coincident, but the average speed of the heavier species is slightly greater than the lighter one. By working in the few Kelvin regime, this relatively simple technique reduces the number of partial waves in the collision process, which allows the observation of collision resonances. Additionally, copropagation of scattering partners in a single molecular beam precisely defines the direction of their relative velocity vector, which is essential for the study of stereodynamics.

    更新日期:2018-06-03
  • 更新日期:2018-06-03
  • Molecular dynamics of the two-stage mechanism of cyclopentadiene dimerization: concerted or stepwise?
    Chem. Phys. (IF 1.707) Pub Date : 2018-02-21
    Zhongyue Yang, Luyi Zou, Yanmin Yu, Fengjiao Liu, Xiaofei Dong, K.N. Houk
    更新日期:2018-06-03
  • 更新日期:2018-06-03
  • 更新日期:2018-06-03
  • A thermodynamic-based approach for the resolution and prediction of protein network structures
    Chem. Phys. (IF 1.707) Pub Date : 2018-03-05
    Efrat Flashner-Abramson, Jonathan Abramson, Forest M. White, Nataly Kravchenko-Balasha

    The rapid accumulation of omics data from biological specimens has revolutionized the field of cancer research. The generation of computational techniques attempting to study these masses of data and extract the significant signals is at the forefront. We suggest studying cancer from a thermodynamic-based point of view. We hypothesize that by modelling biological systems based on physico-chemical laws, highly complex systems can be reduced to a few parameters, and their behavior under varying conditions, including response to therapy, can be predicted. Here we validate the predictive power of our thermodynamic-based approach, by uncovering the protein network structure that emerges in MCF10a human mammary cells upon exposure to epidermal growth factor (EGF), and anticipating the consequences of treating the cells with the Src family kinase inhibitor, dasatinib.

    更新日期:2018-06-03
  • Signatures of Anderson localization and delocalized random quantum states
    Chem. Phys. (IF 1.707) Pub Date : 2018-03-06
    Giorgio J. Moro, Giulia Dall'Osto, Barbara Fresch

    We consider the notion of equilibration for an isolated quantum system exhibiting Anderson localization. The system is assumed to be in a pure state, i.e., described by a wave-function undergoing unitary dynamics. We focus on the simplest model of a 1D disordered chain and we analyse both the dynamics of an initially localized state and the dynamics of quantum states drawn at random from the ensemble corresponding to the minimum knowledge about the initial state. While in the former case the site distribution remains confined in a limited portion of the chain, the site distribution of random pure state fluctuates around an equilibrium average that is delocalized over the entire chain. A clear connection between the equilibration observed when the system is initialized in a fully localized state and the amplitude of dynamical fluctuations of a typical random pure state is established.

    更新日期:2018-06-03
  • Electron injection from a carboxylic anchoring dye to TiO2 nanoparticles in aprotic solvents
    Chem. Phys. (IF 1.707) Pub Date : 2018-03-15
    Hui Fang, Yuhao Wu, Danielle L. Kuhn, Zachary Zander, Brendan G. DeLacy, Yi Rao, Hai-Lung Dai
    更新日期:2018-06-03
  • Theoretical investigation on vibrational frequency fluctuations of SCN-derivatized vibrational probe molecule in water
    Chem. Phys. (IF 1.707) Pub Date : 2018-03-15
    Masaki Okuda, Masahiro Higashi, Kaoru Ohta, Shinji Saito, Keisuke Tominaga
    更新日期:2018-06-03
  • A local instantaneous surface method for extracting membrane elastic moduli from simulation: Comparison with other strategies
    Chem. Phys. (IF 1.707) Pub Date : 2018-03-16
    Christoph Allolio, Amir Haluts, Daniel Harries

    Advances over the past decade have made it possible to extract elastic constants of lipid assemblies from molecular dynamics simulations. We summarize existing strategies for obtaining membrane elastic moduli and clarify the differences in the underlying approaches. We analyze these strategies in depth, including several important advantages and limitations. By addressing these limitations, we obtain a newly formulated spatially local methodology for extracting bending and tilt moduli: The Real Space Instantaneous Surface Method (ReSIS). With its freely available implementation, this method is designed for highly dynamic systems with arbitrary interface geometries. We demonstrate how the method provides consistent results for membranes of arbitrary size. In addition, we describe alternative implementations of various Fourier-space methods, and use these to compare the results from the different available methods and from published computational data. We specifically focus on the tilt modulus, where very large differences between Fourier and real-space based methods are observed, including those derived using ReSIS. These discrepancies are likely due to the known difference between model moduli and thermodynamic moduli that are derived from the corresponding response functions. In addition, we reexamine the issue of angular degeneracy and its effect on conformational ensembles. Finally, a van ’t Hoff analysis of the tilt and bending moduli reveals that both modes act as entropic springs and that enthalpy favors nonzero tilt, perhaps heralding the spontaneous lipid chain tilt of the gel phase at lower temperatures.

    更新日期:2018-06-03
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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