Chemical Physics Letters (v.471, #1-3)
Editorial Board (IFC).
Analysing the chromium–chromium multiple bonds using multiconfigurational quantum chemistry by Marcin Brynda; Laura Gagliardi; Björn O. Roos (1-10).
Multiconfigurational quantum chemistry study of Cr–Cr multiple bonds.This Letter discusses the nature of the chemical bond between two chromium atoms in different di-chromium complexes with the metal atoms in different oxidation states. Starting with the Cr diatom, with its formally sextuple bond and oxidation number zero, we proceed to analyse the bonding in some Cr(I)–Cr(I) XCrCrX complexes with X varying from F, to Phenyl, and Aryl. The bond distance in these complexes varies over a large range: 1.65–1.83 Å and we suggest explanations for these variations. A number of di-chromium complexes with bond distances around or shorter than 1.80 Å have recently been synthesized and we study one of these complexes, Cr2(diazadiene)2 and show how the Cr–Cr bond order is related to the oxidation number and the ligand bonding, factors that are all involved in the determination of the short Cr–Cr bond length: 1.80 Å. The discussion is based on the use of multiconfigurational wave functions, which give a qualitatively correct description of the electronic structure in these multiply bonded systems.
In situ growth of SnO2 nanowires on the surface of Au-coated Sn grains using water-assisted chemical vapor deposition by Wenyan Yin; Bingqing Wei; Changwen Hu (11-16).
SnO2 nanowires have been directly synthesized on the surface of Au-coated Sn grains using a water-assisted chemical vapor deposition method.SnO2 nanowires (NWs) have been directly synthesized in high-yield on the surface of Au-coated Sn grains using a water-assisted chemical vapor deposition (CVD) method. The Au-coated Sn grains served themselves as both the Sn source, which reacted with H2O vapor at 700–800 °C under the flow of high purity N2 carrier, and the substrate for the growth of the SnO2 NWs. The synthesized SnO2 NWs were systematically studied using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The single-crystalline SnO2 NWs are about 100–150 μm in length and 16–60 nm in diameter, which can be tuned by simply adjusting the CVD temperature. A possible formation mechanism of SnO2 NWs was proposed and discussed. Gas sensors based on SnO2 NWs prepared at 800 °C exhibited excellent sensing performance, characterized with excellent selectivity and fast response time to ethanol vapor and H2S gas operating at 320 °C.
Carbohydrate–aromatic interactions: A computational and IR spectroscopic investigation of the complex, methyl α-l-fucopyranoside · toluene, isolated in the gas phase by Zheng Su; Emilio J. Cocinero; E. Cristina Stanca-Kaposta; Benjamin G. Davis; John P. Simons (17-21).
Modelling protein–sugar interactions: an IR and computational investigation of a stacked molecular complex.A carbohydrate–aromatic complex, methyl α-l-fucopyranoside · toluene, which provides a model for probing the physical basis of carbohydrate–protein ‘stacking’ interactions, has been created in a molecular beam and probed through IR ion dip spectroscopy in the CH and OH regions. The results are interpreted in the light of DFT calculations using the MO5-2X functional. They indicate the creation of stacked structures with the aromatic molecule bonded either to the upper or to the lower face of the pyranoside ring, through CH3,4–π (upper) or CH1–π (lower) interactions leading to binding energies ⩽18 kJ mol−1.
Ab-initio calculation of the ground and excited states of MgH using a pseudopotential approach by J.-M. Mestdagh; P. de Pujo; B. Soep; F. Spiegelman (22-28).
Ground and excited states of MgH using a pseudopotential approach.The electronic structure of the MgH molecule is investigated using a pseudopotential description of the Mg 2 + core, complemented by a core polarization operator. The electronic problem is treated by the Internally Contracted Multi-Reference Configuration Interaction method (IC-MRCI). The potential energy curves and the molecular constants are calculated for all MgH molecular states dissociating up to the excited atomic configurations Mg(3s3d1D) + H(1s2S). A good agreement with the available experimental data is found. These calculations help to clarify the very complicated spectroscopy of MgH in the 35 000–46 000 cm - 1 excitation range, where many states correlated with the 3s3p, 3s4s and 3s3d atomic configurations cross one another. For instance, the predissociation mechanism of the B 2 Σ + state is enlighten. Both the doublet and quartet systems are documented.
Excitation spectra of CdRg (Rg = He, Ne, Xe) complexes recorded at the D 1 Σ 0 + ← X 1 Σ 0 + transition: From the heaviest CdXe to the lightest CdHe by M. Strojecki; M. Krośnicki; M. Łukomski; J. Koperski (29-35).
Analysis and simulation of the free ← bound and bound ← bound profiles recorded for the first-time in excitation spectra using the D 1 Σ 0 + ← X 1 Σ 0 + transition yield information on the D 1 Σ 0 + -state potential of the CdHe, CdNe and CdXe complexes.Laser-induced fluorescence excitation spectra of CdRg (Rg = He, Ne, Xe) complexes were recorded at the D 1 Σ 0 + ← X 1 Σ 0 + bound ← bound and free ← bound transitions. In case of CdXe, analysis of the recorded profiles resulted in determination of the D 1 Σ 0 + -state potential energy curve and ground-state dissociation energy. In case of CdHe and CdNe, analysis of the free ← bound profiles provided a repulsive part of the D 1 Σ 0 + -state potential. Valence ab initio calculations of the ground- and excited-state potentials and electronic transition dipole moments of the studied transition were performed taking scalar-relativistic and spin-orbit effects into account. The results were supplemented with those for CdAr and CdKr of our earlier study.
Hydrogen bonding interaction in complexes of hydronium ion with selective chemical species by Ravi Joshi; Tapan K. Ghanty; Sergej Naumov; Tulsi Mukherjee (36-40).
The order of binding energies of (H3O··· AB)+ systems as calculated with UCCSD(T)/aug-cc-pVTZ method has been found to follow an order: HCN > H2 O > HOO > OH > SH > HF > HBr > HCl > ON > NO.The structure and hydrogen bonding in dimer cation systems of H3O+ with some chemical species have been studied using DFT/B3LYP and MP2 with 6-311++G(d,p) basis set, and CCSD/aug-cc-pVTZ methods. The order of binding energies of the studied system, (H3O⋯AB)+, as calculated with UCCSD(T)/aug-cc-pVTZ method follow an order: HCN > H2 O > HOO > OH > SH > HF > HBr > HCl > ON > NO. The structure of (H3O⋯AB)+ can be described as a hydrogen-bonded complex of H3O+ with AB in which the hydrogen atom from H3O+ makes a hydrogen bond with A-atom of AB species.
Effect of the vibrational excitation on the non-radiative deactivation rate of the S1 state of p-cresol(NH3) complex by A.N. Oldani; M. Mobbili; E. Marceca; J.C. Ferrero; G.A. Pino (41-44).
The CH3 group in p-cresol introduces low frequency modes and thus an increased density of states at low values of energy that facilitates the coupling of the intermolecular modes with those of the p-cresol moiety.The effect of the CH3 group on the lifetime of the S1 state of the p-cresol(NH3) complex was investigated by means of REMPI, LIF, DF spectroscopy and ab initio calculations.At variance with PhOH(NH3) for which vibrational-mode specificity was reported, the lifetime of the S1 state of the p-cresol(NH3) complex decreases monotonically upon vibrational excitation indicating that randomization of energy takes place at low excitation energy. This result is analyzed as the consequence of a stronger coupling of the complex intermolecular modes with those of the CH3 group.
Observation of collision-induced near-IR emission of singlet oxygen O2 a1Δg generated by visible light excitation of gaseous O2 dimol by Eiji Furui; Nobuyuki Akai; Akira Ida; Akio Kawai; Kazuhiko Shibuya (45-49).
The dimol absorption of O2 at 630 nm was performed to selectively generate singlet oxygen O2 a1Δg in the gas phase.The dimol absorption of O2 at 630 nm was performed to generate O2 a1Δg in the gas phase. The pure collision-induced phosphorescence spectrum was recorded around 1260 nm at the O2 pressure of 130 atm. The excitation spectrum, recorded by measuring the near-IR emission intensity, had the same spectral shape as that of the dimol absorption spectrum in 620–640 nm. The quadratic pressure dependence of the phosphorescence intensity evidenced that the emission was induced by collision. The self-quenching rate constant of O2 a1Δg has been estimated to be (1.7 ± 0.2) × 10−18 cm3 molecule−1 s−1.
Infrared spectroscopy for acetone and its dimer based on photoionization detection with tunable coherent vacuum-ultraviolet light by Yoshiyuki Matsuda; Keisuke Ohta; Naohiko Mikami; Asuka Fujii (50-53).
Infrared spectroscopy based on VUV photoionization detection is carried out for acetone and its dimer with tunable coherent VUV light.Infrared (IR) spectroscopy based on vacuum-ultraviolet (VUV) one-photon ionization detection is carried out for bare acetone and its dimer by use of tunable coherent VUV light. This is the first application of tunable VUV light to IR spectroscopy of a size-selected cluster, which has no suitable chromophore for conventional detection schemes. The advantage of this spectroscopic scheme is demonstrated. The observed IR spectrum of acetone dimer indicates formation of a C2h symmetric structure, where the acetone molecules stack with an antiparallel orientation of the carbonyl groups.
A new ab initio potential energy surface for the Ne–H2 interaction by François Lique (54-58).
Contour plot of the analytical ground potential energy surface of the NeH2 system, as a function of Jacobi coordinates R and θ, obtained from ab initio calculations at the single and double excitation coupled-cluster method with noniterative perturbational treatment of triple excitation [CCSD(T)]. The H2 bond length is held fixed to 1.44 bohr.A new accurate three-dimensional potential energy surface for the Ne–H2 system, which explicitly takes into account the r-dependence of the H2 vibration, was determined from ab initio calculations. It was obtained with the single and double excitation coupled-cluster method with noniterative perturbational treatment of triple excitation [CCSD(T)]. Calculations was been performed using the augmented correlation-consistent polarized quintuple zeta basis set (aug-cc-pV5Z) for the three atoms.We checked the accuracy of the present ab initio calculations. We have determined, using the new Ne–H2 potential energy surface, differential cross-sections for the rotational excitation of the H2 and D2 molecules in collision with Ne and we have compared them with experimental results of Faubel et al. [M. Faubel, F.A. Gianturco, F. Ragnetti, L.Y. Rusin, F. Sondermann, U. Tappe, J.P. Toennies, J. Chem. Phys. 101 (1994) 8800]. The overall agreement confirms that the new potential energy surface can be used for the simulation of molecular collisions and/or molecular spectroscopy of the van der Waals complex Ne–H2.
State-to-state quasi-classical trajectory study of the F + CH2D2 reaction by Joaquín Espinosa-García (59-64).
State-to-state quasi-classical trajectory study of the F + CH2D2 gas-phase reaction.The reaction of fluorine atoms with bideuterated methane can evolve along two paths, D- and H-abstraction. On an analytical potential energy surface (PES-2006) recently developed by our research group, quasi-classical trajectory (QCT) calculations were performed at different collision energies. The dynamics properties of the two paths – vibrational and rotational distributions, product energy partitioning, excitation functions and scattering distributions – are in general similar, suggesting the idea of an almost similar importance of the two mechanisms, with the H-abstraction being slightly favoured. Comparison with the scarce experimental information shows reasonable agreement, and the differences could be due to deficiencies of the PES, but also to the known limitations of the QCT method.
Quasi-classical determination of integral cross-sections and rate constants for the N + OH → NO + H reaction by M. Jorfi; P. Honvault; P. Halvick (65-70).
Theoretical and experimental rate constant (in cm 3 molecule - 1 s - 1 ) as a function of the temperature for the N + OH → NO + H . The k 00 rate constant for the N + OH ( v = 0 , j = 0 ) → NO + H reaction, obtained using our QCT method, is also plotted for comparisonQuasi-classical trajectory (QCT) calculations have been carried out for the N + OH → NO + H reaction on an ab initio global potential energy surface for the ground electronic state, X 3 A ″ . Cross-sections, computed for collision energies between 0.001 and 1 eV, show no energy threshold and decrease with the increasing collision energy. Rate constants have been calculated in the 5–500 K temperature range. The thermal rate constant is in good agreement with previous theoretical results over a wide range of temperatures, and with the experimental data for temperatures above 300 K. Cross-sections and rate constants are found to be dependent on the initial rotation.
Reorientation of HDO in liquid H2O at different temperatures: Comparison of first and second order correlation functions by K.J. Tielrooij; C. Petersen; Y.L.A. Rezus; H.J. Bakker (71-74).
The reorientation of water molecules changes from 4.8 ± 0.3 ps at 1 °C to 0.97 ± 0.05 ps at 70 °C. This acceleration can be explained from the overall weakening of the hydrogen bonds.We study the temperature dependence of the molecular reorientation of HDO molecules in H2O with polarization-resolved femtosecond mid-infrared pump–probe spectroscopy. With this technique we measure the decay time of the second order correlation function of the molecular reorientation. We find that the reorientation time changes from 4.8 ± 0.3 ps at 1 °C to 0.97 ± 0.05 ps at 70 °C. We compare the measurements with literature results of Terahertz time domain spectroscopy, where the Debye reorientation time is measured. From this comparison we obtain the ratio between the Debye reorientation time and the first order single molecule reorientation time.
Ti 3p electrons: Core or valence? by N. Aaron Deskins (75-79).
Density functional modeling of Au adsorption over the TiO2 (1 1 0) surface is used to evaluate the role of Ti semicore 3p electrons.The debate over whether Ti 3p electrons should be treated as core or valence electrons when using pseudopotential-based density functional theory is addressed. Two pseudopotentials that treat the 3p electrons either as core or valence are compared by modeling bulk TiO2 and Ti, TiO2 surface adsorption and reduction, as well as TiCl x reactions. The present study shows that the 3p electrons can often be treated as core states, but frozen 3p electrons may be unsuitable for processes involving large electronic changes (for example charge transfer or chemical bonding).
Characterization of local structures in amorphous and crystalline tris(8-hydroxyquinoline) aluminum(III) (Alq3) by solid-state 27Al MQMAS NMR spectroscopy by Yusuke Nishiyama; Tatsuya Fukushima; Kousuke Takami; Yasunari Kusaka; Toshio Yamazaki; Hironori Kaji (80-84).
27Al NMR spectra show two components in α-Alq3 and the amount of the facial isomer in amorphous Alq3.The local structure of tris(8-hydroxyquinoline) aluminum(III) (Alq3) in three different crystalline polymorphs, α-, γ-, and δ-Alq3, and amorphous Alq3, are investigated by 27Al NMR experiments, which include two-dimensional multi-quantum magic-angle spinning (MQMAS) experiments and one-dimensional variable B 0 field MAS experiments. The quadrupolar and chemical shift parameters of these Alq3 samples are determined, including the distributions. These parameters reflect the local structure of respective samples and it is found that the γ- and δ-Alq3 consist of the facial isomer with well-defined crystal structure, whereas the α- and amorphous Alq3 consist of the meridional isomer with distributions of quadrupolar coupling constants. It is also found that two distinct components exist in α-Alq3.
Broadband dielectric response of dichloromethane by Johannes Hunger; Alexander Stoppa; Andreas Thoman; Markus Walther; Richard Buchner (85-91).
Dynamics of dichloromethane are dominated by isotropic rotational diffusion in the GHz region and two librational modes at THz frequencies.A systematic study of the dielectric response of dichloromethane over a broad frequency range ( 8.5 ⩽ ν / GHz ⩽ 1000 ; ⩽ 4.3 THz at 25 °C) at temperatures from 5 to 35 °C is reported. The spectra are best described by a superposition of three contributions. The dominating loss peak at ∼ 70 GHz , fitted by a modified Debye equation accounting for inertial rise, represents the rotational diffusion of molecular dipoles. Additionally, two libration modes contribute, which are described by damped harmonic oscillators of resonance frequencies ∼ 0.9 THz and ∼ 2.1 THz . While the latter modes reflect the anisotropy of the dichloromethane molecule, the diffusive reorientation at long times appears to be rather isotropic.
Influence of protonation upon the conformations of bipiperidine, bimorpholine, and their derivatives by Merle Uudsemaa; Marju Laars; Kadri Kriis; Toomas Tamm; Margus Lopp; Tõnis Kanger (92-96).
Intramolecular hydrogen bonding determines the most stable conformations of protonated N-isopropyl-bipiperidine (left) and N-isopropyl-bimorpholine (right).Bimorpholine and bipiperidine are efficient organocatalysts. Stereoselectivity of reactions catalysed by bimorpholine and bipiperidine strongly depend on their protonation – only the protonated form of the catalyst leads to stereoselective reactions. In this study the conformations of these compounds, as well as some reaction intermediates, are investigated computationally. Significant changes in the conformations are observed when the compounds are protonated, caused by intramolecular hydrogen bonding.
Selective interaction of a soluble pentacene derivative with metallic single-walled carbon nanotubes by Cai-Hong Liu; Yi-Yang Liu; Yong-Hui Zhang; Rui-Rui Wei; Bing-Rui Li; Hao-Li Zhang; Yong Chen (97-102).
Extraction of metallic single-walled carbon nanotubes has been accomplished through noncovalent complexation of nanotubes with a soluble pentacene derivative.We report a soluble pentacene derivative, 6,13-bis(2-(trimethylsilyl)ethynyl)pentacene, can be used for efficient extraction of metallic single-walled carbon nanotubes (SWCNTs), which is proven by resonance Raman spectroscopy (RRS), Vis–NIR absorption spectroscopy and conductivity measurements. RRS studies reveal that the separation is solvent-dependent and is more efficient for small diameter tubes. Theoretical simulation suggests that the adsorption of pentacene on (7, 7) metallic SWCNT is about 34% more favorable than that on (13, 0) semiconducting SWCNT. This work provides a new direction in seeking reagents to facilitate high efficiency and nondestructive separation of metallic and semiconducting SWCNTs.
Highly aligned carbon nanotube/polymer composites with much improved electrical conductivities by Huisheng Peng; Xuemei Sun (103-105).
Highly aligned carbon nanotube/polymer composites with much improved conductivities have been synthesized.Carbon nanotube (CNT)/polymer composites are generally synthesized by coating CNT/polymer mixture solutions into films or powders. A main challenge is that CNTs are randomly dispersed in derived composites, which results in extremely low electrical conductivities. Here we report the synthesis of highly aligned CNT/polymer composites with much improved conductivities by incorporating polymers into aligned CNT arrays. The key point in this work is to grow dense and robust CNT arrays through a chemical vapor deposition process.
Frequency-controllable electric field distribution in colloidal crystals by L.F. Zhang; J.P. Huang; K.W. Yu (106-110).
We convincingly reveal that electric field distributions in colloidal crystals are controllable by tuning the frequency of an incident light.The study of electric field distributions in graded systems is important due to various applications. We establish an analytical method based on the Maxwell equations, to investigate electric field distributions in graded multilayered colloidal crystals. This analytical method agrees very well with an existing numerical method. It convincingly explains and confirms the fact that the peak of electric field distributions is controllable to appear in a specific layer, by tuning the angular frequency of an incident light. Also, this method offers a more convenient way to the understanding of electric field distributions in colloidal crystals.
Theoretical investigation on the polarizability and second hyperpolarizability of polysilole by Benoît Champagne; Milena Spassova (111-115).
Small bond length alternation along the conjugated backbone confers on polysilole chains substantial second hyperpolarizability per unit cell.The polarizability and second hyperpolarizability of polysilole chains containing 2–9 silole units have been calculated ab initio. The MP2/6-31G∗ longitudinal polarizability per silole unit converges towards 324 au, which is at least of semi-quantitative accuracy because basis set and electron correlation effects compensate each other. On the other hand, the second hyperpolarizability per silole unit does not show any sign of leveling off, demonstrating substantial electron delocalization effects associated with a small bond length alternation. These second hyperpolarizabilities are amongst the largest values reported so far, though they remain a factor of 2–3 smaller than in polybutatriene.
Heterofullerene molecules C58X (X = S, Se, Te): A DFT study by Feng-Ling Liu (116-121).
Density functional calculations at the B3LYP/6–31G∗ level of theory have been employed to heterofullerenes C58X (X = S, Se, Te).The novel heterofullerenes C58X (X = S, Se, Te) have been reported here. They all have odd number of atoms assembling the heterofullerene-cage. Density functional calculations and minimization techniques have been employed to characterize the structural and electronic properties of them. Vibrational frequencies of them have been calculated at the B3LYP/6-31G∗ level of theory. The absence of imaginary vibrational frequency confirms that they all correspond to true minima on potential energy hypersurface. Their heats of formation were estimated. According to the HOMO–LUMO gaps and heats of formation, they are all less stable than C60 and the stable rank of them is C58S < C58Se < C58Te. We proposed their prepared route here.
An effective sonication-assisted reduction approach to synthesize highly dispersed Co nanoparticles on SiO2 by Wallace Tse Loong Lim; Ziyi Zhong; Armando Borgna (122-127).
A simple sonication-assisted reduction method allows for the synthesis of highly dispersed and uniform Co nanoparticles on SiO2.A sonication-assisted method to synthesize supported Co/SiO2 nanoparticles was developed using NaBH4 as reducing agent. Co nanoparticles with an average size of 2.4 nm were obtained. Further fine-tuning of the particle size was achieved by adding stabilizer. TEM and XPS confirmed that the dispersion was significantly improved by using sonication. After calcination at 400 oC or 600 oC for 2 h, the size of the Co3O4 nanoparticles was increased to ca. 8 and 11 nm, respectively. Traces of Co2SiO4, B2O3 and Co(B4O7) were also detected after calcination at high temperatures. This method provides a new approach to the controlled synthesis of supported transition metal nanoparticles.
Interaction and photobinding between 8-methoxypsoralen and thymine by Salama Omar; Leif A. Eriksson (128-132).
The photochemical [2+2] cycloadditions between 8-methoxypsoralen and thymine are investigated computationally.The intercalation and photobinding of 8-methoxypsoralen with thymine in DNA is studied by computational chemistry techniques. Photochemical [2+2] cycloadditions at the S1 surface display barriers of approximately 20 kcal/mol. The lowest lying excited surface has a defined potential well at the ground state TS, enabling for efficient decay. Avoided crossings between the S1 and S2 surfaces are also observed, which may influence the photochemical reactivity. The further reactions leading to crosslink formation from furan monoadducts but not from pyrone ones are fully explained by the excitation energies of the monoadducts, whereas the predominance of furan over pyrone monoadduct formation is not explained looking at the excitation energy surfaces alone.
DFT calculation of pKa’s for dimethoxypyrimidinylsalicylic based herbicides by Eduardo J. Delgado (133-135).
The acid-dissociation constants, pKa, of dimethoxypyrimidinylsalicylic derived herbicides are calculated by DFT methods.Dimethoxypyrimidinylsalicylic derived compounds show potent herbicidal activity as a result of the inhibition of acetohydroxyacid synthase, the first common enzyme in the biosynthetic pathway of the branched-chain aminoacids (valine, leucine and isoleucine) in plants, bacteria and fungi. Despite its practical importance, this family of compounds have been poorly characterized from a physico-chemical point of view. Thus for instance, their pKa’s have not been reported earlier neither experimentally nor theoretically. In this study, the acid-dissociation constants of 39 dimethoxypyrimidinylsalicylic derived herbicides are calculated by DFT methods at B3LYP/6-31G(d,p) level of theory. The calculated values are validated by two checking tests based on the Hammett equation.
Is the LEPS potential accurate enough to investigate the dissociation of diatomic molecules on surfaces? by L. Martin-Gondre; C. Crespos; P. Larregaray; J.C. Rayez; B. van Ootegem; D. Conte (136-142).
We propose an improved version of the standard periodic LEPS potential energy surface for the study of diatom-surface reactions.Potential energy surface accuracy is one key issue within the framework of dynamics simulation of gas-surface reactions. Regarding dissociative adsorption of diatomic molecules, the analytical periodic LEPS function hardly reproduces all the intricate structures of the diatom-surface interaction. In this work, we propose an extended version of the standard periodic LEPS including: (i) the implementation of surface-site-dependent Sato parameters, (ii) the addition of Gaussian functions representing entrance channel barriers. This flexible periodic LEPS potential is shown to lead to reliable predictions of the N 2 dissociative adsorption probability on W(1 0 0).
First principle simulation of vibrationally resolved A 2 B 1 ← X ˜ 2 A 1 electronic transition of phenyl radical by Malgorzata Biczysko; Julien Bloino; Vincenzo Barone (143-147).
First principles, full-dimensional simulation of vibrationally resolved electronic spectrum of phenyl radical.The A 2 B 1 ← X ˜ 2 A 1 electronic transition of phenyl radical has been studied by a recently introduced procedure to compute vibrationally resolved electronic spectra from first principles. Structural and vibrational properties have been obtained with the B3LYP/TD-B3LYP//N07D model, designed for computational studies of free radicals. The Franck–Condon Herzberg–Teller (FC-HT) spectra computed taking into account changes in structures, normal modes, and vibrational frequencies between both electronic states closely resemble their experimental counterpart. It is shown that full-dimensional vibronic models are necessary to reproduce correctly the spectrum shape and should be fully exploited prior to analyze the possible role of nonadiabatic effects.
Modelling the polarizability of the dihydrogen–argon pair by Tadeusz Bancewicz; George Maroulis (148-152).
The system of the Cartesian axes defining the angle 〈theta〉 and the relative intermolecular separation R used in our computations.The collision-induced (CI) pair polarizability of dihydrogen–argon ( H 2 – Ar ) pair has been studied using quantum-chemical and analytical methods. We have proposed a procedure to determine the rotationally adapted (symmetry adapted) components of the CI polarizability tensor. The corresponding irreducible spherical symmetry adapted components are computed for the H 2 – Ar pair. We have analyzed the dipole-induced dipole (DID) model pair polarizability tensor for H 2 – Ar . Good agreement between the DID allowed rotationally adapted CI H 2 – Ar polarizability components and those computed by quantum-chemical methods is found.
Evaluation of instrument response functions for lifetime imaging detectors using quenched Rose Bengal solutions by Mariusz Szabelski; Rafal Luchowski; Zygmunt Gryczynski; Peter Kapusta; Uwe Ortmann; Ignacy Gryczynski (153-159).
In this work we present an ultra-short fluorescence standard in the orange-red region which has a lifetime of 16 ps.Instrument response functions (IRF) in time-domain fluorescence are usually recorded as reflected or scattered excitation light, which is at shorter wavelengths than the observed fluorescence emission. However, its often more appropriate to measure the IRF in the emission spectral region. In this work we show that Rose Bengal water solutions quenched by potassium iodide can be used to measure instrument response functions of single photon detectors in the orange-red wavelength region. We used the quenched RB emission as a reference in time-domain measurements with common detectors and we got practically the same results as with scattering.
Quasi-classical trajectory study of the reaction H + FO → OH + F by Juan Zhao; Yan Xu; Daguang Yue; Qingtian Meng (160-162).
QCT calculations are carried out for the reaction H + FO(0, 0) → OH + F on the PES of the ground 3A″ triplet state.Quasi-classical trajectory (QCT) calculations are carried out for the reaction H + FO(0, 0) → OH + F on the adiabatic potential energy surface (PES) of the ground 3A″ triplet state [S. Gómez-Carrasco, L. González-Sánchez, A. Aguado, M. Paniagua, O. Roncero, M.L. Hernández, J.M. Alvarino, Chem. Phys. Lett. 383 (2004) 25]. The reaction probability for total angular momentum j = 0 has been calculated, and the integral cross sections as a function of collision energy have been presented. The calculated results with QCT are found to be well consistent with the new quantum mechanical wave packet results calculated by Chu et al. The product rotational alignments have also been calculated and the 〈 P 2 ( j ′ · k ) 〉 values are almost invariant with collision energies.
Polaron transport between DNA segments: annihilating and creating by Guiqing Zhang; Peng Cui; Jian Wu; Chengbu Liu (163-167).
Coherent vibrations of the lattices and the two couplings make the polaron get through wide potential barriers. The charge density |ψn |2 transfers along the chain of A30T40G30 from 0 to 3.0 ps.Segments of the DNA are calculated with the Peyrard–Bishop–Holstein model. The results show that the two controversial charge transport mechanisms, hopping and tunneling, are not consummate to depict its behaviors along the DNA chains composed of R n R m ′ R p ″ , in which the polaron will annihilate gradually and meanwhile new one will be created at some new ones in the presence of an electric field. We speculate the phenomenon can be explained by the collective vibration of the lattices and the two intensity couplings: one is between lattices and a charge; the other is hydrogen bond interaction between complementary bases.
Electrophilicity of quinones and its relationship with hydride affinity by Paola R. Campodónico; Arie Aizman; Renato Contreras (168-173).
The electrophilicity index assesses well the hydride affinity (HA) order of quinones. Comparisons with predicted HA values for a larger data base suggest that both the electrophilicity index and the HA are tightly related quantities. These results open the possibility of predicting HA for quinones not evaluated experimentally up to date.In this Letter we show that the electrophilicity index assesses well the hydride affinity (HA) order of quinones established for a limited number of cases experimentally observed. Further comparisons with predicted HA values for a larger data base suggest that both the electrophilicity index and HA are tightly related quantities. Furthermore, electrophilic activation/deactivation patterns induced by electron-withdrawing and electron-donating groups may be consistently accounted for by the model. These results open the possibility of predicting HA for quinones not evaluated experimentally up to date.
Bond metallicity of materials from real space charge density distributions by S. Jenkins; P.W. Ayers; S.R. Kirk; P. Mori-Sánchez; A. Martín Pendás (174-177).
A real space local measure of metallicity is linked with existing global metallicity measures and a transferability rule is devised.Within the framework of the theory of atoms in molecules, AIM, it was recently proposed that the metallicity of a bond could be determined from the properties of the electron density at the bond critical point using the ratio ξJ ( r bcp ) = ρ( r bcp )/∇2 ρ( r bcp ). In this study we have mined results published using AIM and considered three different local measures of the bond metallicity: the original metallicity definition ξJ ( r bcp ), a dimensionless metallicity indicator, ξm ( r bcp ), and the value of Bohm’s quantum potential at the bond critical point. A global measure of metallicity, the planarity index f, has also been examined. We focus this study on a broad range of elements, ions and compounds of the form of the later is Mp Xq , where 1 ⩽ p ⩽ 2 and 1 ⩽ q ⩽ 4. A pressure induced non-metallic–metallic phase transitionbonds of the Ge3N4 for the β- and γ-crystals is observed. The various metallicity measures agree well with experimental observations and are observed to give qualitatively similar results.