Probing the ultrafast photoelectron spectra of Br2 molecule

The time‐dependent‐wave‐packet method is applied to study the ionization of Br₂ molecule with four ionization processes. The ground state absorption makes the photoelectron to be left in the three final ionic states: Br (X²∑), Br (A²∏_u), and Br (B²∑), and each population of these ionic states is related with the laser intensities. The information of the dissociation can be got by analyzing the photoelectron features of the transient wave packet, which also suggests that an ionization process occurs during the dissociation, and the Br atoms that mainly resulted from the dissociation of Br₂ (C¹∏_u) are ionized at later time delays as the dissociation is nearly complete. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

The natural abundance of 15N in plant and soil‐available N indicates a shift of main plant N resources to NO from NH along the N leaching gradient

To investigate which of ammonium (NH) or nitrate (NO) is used by plants at gradient sites with different nitrogen (N) availability, we measured the natural abundance of ¹⁵N in foliage and soil extractable N. Hinoki cypress (Chamaecyparis obtusa Endlicher) planted broadly in Japan was selected for use in this study. We estimated the source proportion of foliar N (NH vs. NO) quantitatively using mass balance equations. The results showed that C. obtusa used mainly NH in N‐limited forests, although the dependence of C. obtusa on NO was greater in other NO‐rich forests. We regarded dissolved organic N (DON) as a potential N source because a previous study demonstrated that C. obtusa can take up glycine. Thus we added DON to our mass balance equations and calculated the source proportion using an isotope‐mixing model (IsoSource model). The results still showed a positive correlation between the calculated plant N proportion of NO and the NO pool size in the soil, indicating that high NO availability increases the reliance of C. obtusa on NO. Our data suggest the shift of the N source for C. obtusa from NH to NO according to the relative availability of NO. They also show the potential of the foliar δ¹⁵N of C. obtusa as an indicator of the N status in forest ecosystems with the help of the δ¹⁵N values of soil inorganic and organic N. Copyright © 2010 John Wiley & Sons, Ltd.     

Bound‐states of diatomic molecules in the Dirac equation with the q‐deformed Morse potential

We present the solutions of the ro‐vibrational motion of a diatomic molecule with a spatially dependent mass by solving the Dirac equation with position‐dependent mass for repulsive vector $V(r)$ and attractive scalar $S(r)$ q‐deformed Morse potential for any $\kappa$ value, within the framework of Pekeris approximation of the spin‐orbitcoupling term. The relativistic energy spectra are obtained using theNikiforov‐Uvarov method and the two‐component spinor wavefunctions are obtained in terms of the Laguerre polynomials. It is found that there exist only negative energy states for bound states, and the energy values for a fixed value of $n_r$ increase with decrease in $\kappa$ . © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

A method to calculate the one‐electron reduction potentials for nitroaromatic compounds based on gas‐phase quantum mechanics

Nitroaromatic compounds (NACs) are widespread environmental contaminants, and the one‐electron reduction potential (E) is an important parameter used in modeling their environmental fate. We have identified a method that is both accurate and efficient to predict E values for NACs, using gas‐phase quantum mechanics (QM) calculations combined with empirical correlations. First, the adiabatic electron affinity (EA) at 0 K is calculated using the B98/MG3S method, and the predictions are scaled by a factor of 0.802 to account for systematic errors in the density functional calculations. Second, the E values are predicted from a linear correlation between E and EA. Using this method, E values were predicted with a mean absolute deviation from measured values of 0.021 V for the 14 NACs used to obtain the correlation and 0.029 V for six additional NACs. This represents a substantial improvement in accuracy over predictions by other QM methods, which are affected by large errors in solvation or aqueous‐phase calculations for some compounds. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010.     

New simple method of measuring the surface glass transition temperature of polymers

A lap‐shear joint mechanical testing method has been probed to measure the surface glass transition temperature (T) of the thick bulk films of high‐molecular‐weight polymers. As T, the temperature transition “occurrence of autoadhesion–nonoccurrence of autoadhesion” has been proposed. The influence of chain flexibility, of molecular architecture, of polymer morphology, and of chain ends concentration on the T has been investigated. The correlation between the reduction in T with respect to the glass transition temperature of the bulk (T) and the intensity of the intermolecular interaction in the polymer bulk in amorphous polymers has been found. The effect of surface roughness on T has been discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2012–2021, 2010     

Mechanistic investigation of vibrational fine structure in e‐H2 scattering using local complex potential‐based time dependent wave packet approach

The structural features of vibrational excitation cross‐sections in resonant e‐H₂ scattering have been investigated using a time dependent wave packet approach and a local complex potential to describe the ²Σ H anion. An analysis of the partial contributions to the vibrational excitation cross‐sections reveals that all features of the excitation profile result from simple interference between bound vibrational levels of H₂ and H. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Theoretical study of one‐electron bonds in a series of high‐spin lithium–beryllium–hydrogen clusters: “Valence shell single‐electron repulsion” rule and electron localization function analysis

A series of high‐spin clusters containing Li, H, and Be in which the valence shell molecular orbitals (MOs) are occupied by a single electron has been characterized using ab initio and density functional theory (DFT) calculations. A first type (⁵Li₂, ⁿ⁺¹LiH_n+ (n = 2–5), ⁸Li₂H) possesses only one electron pair in the lowest MO, with bond energies of ～3 kcal/mol. In a second type, all the MOs are singly occupied, which results in highly excited species that nevertheless constitute a marked minimum on their potential energy surface (PES). Thus, it is possible to design a larger panel of structures (⁸LiBe, ⁷Li₂, ⁸Li, ⁴LiH⁺, ⁶BeH, ⁿ⁺³LiH (n = 3, 4), ⁿ⁺²LiH (n = 4–6), ⁸Li₂H, ⁹Li₂H, ²²Li₃Be₃ and ²²Li₆H), single‐electron equivalent to doublet “classical” molecules ranging from CO to C₆H₆. The geometrical structure is studied in relation to the valence shell single‐electron repulsion (VSEPR) theory and the electron localization function (ELF) is analyzed, revealing a striking similarity with the corresponding structure having paired electrons. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Structure and dissociation energy of weakly bound H (n = 5−8) complexes

The geometrical parameters, vibrational frequencies, and dissociation energies for H (n = 5–8) clusters have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The highest level of theory employed in this study is TZ2P CCSD(T). The C₁ structure of H is predicted to be a global minimum, while the C_s structure of H is calculated to be a transition state. Harmonic vibrational frequencies are also determined at the DZP and TZ2P CCSD levels of theory. The dissociation energies, D_e, for H (n = 5–8) have been predicted using energy differences at each optimized geometry, and zero‐point vibrational energies (ZPVEs) are considered to compare with experimental values. The dissociation energies (D_o) have been predicted to be 1.69, 1.65, 1.65, and 1.46 kcal · mol for H, H, H (C₁ symmetry) and H, respectively, at the TZ2P CCSD(T) level of theory. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Determination of relative sensitivity factors during secondary ion sputtering of silicate glasses by Au+, Au and Au ions

In recent years, Au‐cluster ions have been successfully used for organic analysis in secondary ion mass spectrometry. Cluster ions, such as Au and Au, can produce secondary ion yield enhancements of up to a factor of 300 for high mass organic molecules with minimal sample damage. In this study, the potential for using Au⁺, Au and Au primary ions for the analysis of inorganic samples is investigated by analyzing a range of silicate glass standards. Practical secondary ion yields for both Au and Au ions are enhanced relative to those for Au⁺, consistent with their increased sputter rates. No elevation in ionization efficiency was found for the cluster primary ions. Relative sensitivity factors for major and trace elements in the standards showed no improvement in quantification with Au and Au ions over the use of Au⁺ ions. Higher achievable primary ion currents for Au⁺ ions than for Au and Au allow for more precise analyses of elemental abundances within inorganic samples, making them the preferred choice, in contrast to the choice of Au and Au for the analysis of organic samples. The use of delayed secondary ion extraction can also boost secondary ion signals, although there is a loss of overall sensitivity. Copyright © 2009 John Wiley & Sons, Ltd.     

Autocatalytic oxidation of β‐alanine by peroxomonosulfate in the presence of copper(II) ion

Kinetics and mechanism of oxidation of β‐alanine by peroxomonosulfate (PMS) in the presence of Cu(II) ion at pH 4.2 (acetic acid/sodium acetate) has been studied. Autocatalysis was observed only in the presence of copper(II) ion, and this was explained due to the formation of hydroperoxide intermediate. The rate constant for the catalyzed (k) and uncatalyzed (k) reaction has been calculated. The kinetic data obtained reveal that both the reactions are first order with respect to [PMS]. k values initially increase with the increase in [β‐alanine] and reach a limiting value, but k values decrease with the increase in [β‐alanine]. k values increase linearly with the increase in [Cu(II)], whereas k values increase with [Cu(II)]². Furthermore, k values are independent of [acetate], but k values decrease with the increase in acetate. A suitable mechanism has been proposed to explain the experimental observation. The reaction has been studied at different temperatures, and the activation parameters are calculated. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 40: 44–49, 2008     

Experimental and theoretical investigation on binary anionic clusters of AlmBi

Al_mBi (m = 1–12; n = 1–4) binary cluster anions are generated by laser ablation of a sample composed of Al and Bi, and studied by reflectron time‐of‐flight mass spectrometry (RTOF‐MS) in the gas phase. Some clusters with magic numbers are present in the mass spectrum. The structures of Al_mBi (m + n ≤7) clusters are investigated with the density functional theory (DFT) method and the most likely structures are obtained. The calculations of the binding energy (BE), energy gain (Δ) and HOMO‐LUMO gaps confirm that the Al₂Bi cluster has a very stable structure, which agrees well with the experimental results. It is further established that Al₂Bi can be considered as a gas‐phase Zintl analogue that follows Wade's rules and is the analogue of Ga₂Bi and Sn Zintl ions. Copyright © 2009 John Wiley & Sons, Ltd.     

Solvation Chemistry of DL‐Nor‐Valine in Aqueous Mixture of Dipolar Aprotic N,N‐Dimethyl Formamide

In this article, we reported the solubilities of the amino acid DL‐nor‐valine (VAL) at five equidistant temeratures i.e. from 15 to 35 °C in aqueous mixtures of N,N‐dimethyl formamide (DMF). The Standard free energies (ΔG (i)) and entropies (ΔS (i)) of transfer of VAL from water to aqueous mixture of cationophilic dipolar aprotic DMF have been evaluated at 25 °C. The transfer of Gibbs energies (ΔG (i)) and entropies (TΔS (i)) due to the chemical effects have been obtained after elimination of cavity effect, estimated by the scaled particle theory and dipole‐dipole interaction effects, computed by the used of Keesom‐orientation expression. The chemical contribution of transfer energetics of DL‐nor‐valine (VAL) are mainly guided by the composite effects of increased dispersion interaction, basicity effect and decreased acidity, hydrogen bonding effects, hydrophilic hydration and hydrophobic hydration of aqueous DMF mixtures as compared to that of reference solvent, water.     

Maximum carbonyl‐coordination number of scandium Computational study of Sc(CO)n (n = 1–7), Sc(CO)7− and Sc(CO)63−

Understanding the maximum bonding ability is very important with the potential both to design new compounds and to broaden chemists' imagination. While the coordination ability of the late transition metals has been richly understood, that of scandium is very poor. In this work, a detailed computational study on the equilibrium geometries, stability and vibrational frequencies of a series of Sc(CO)_n (n = 1–7), Sc(CO) and Sc(CO) is reported using density functional theory functionals and the coupled cluster (single‐point) method with 6‐311+G(3df) basis set. It was shown that the obtained sequential and average CO binding energies of Sc(CO)_n (n = 4–7), Sc(CO) and Sc(CO) are comparable to those of the experimentally known species, i.e., smaller Sc‐carbonyls (n ≤3) and the analog Ti(CO)₇⁺. Thus, the studied high scandium carbonyls could all be experimentally accessible. In addition, the studied Sc(CO)_n generally favor the low‐spin ground state (doublet) structures except ScCO and Sc(CO)₃ that are in the quartet states. The previously uncertain spectrum bands were assigned to Sc(CO)₄ and Sc(CO)₅ in this work. In all, the appreciable stability suggested that the last 18‐electron first‐row transition metal carbonyls, that is, Sc(CO) and Sc(CO), could be accessible in experiment. © 2013 Wiley Periodicals, Inc.     

The adsorption of CO2, H2CO3, HCO3− and CO32− on Cu2O (111) surface: First‐principles study

The adsorption of CO₂, and its derivatives, H₂CO₃, HCO, and CO, on Cu₂O (111) surface has been investigated by first‐principles calculations based on the density functional theory at B3LYP hybrid functional level. The Cu₂O (111) surface has been modeled using an embedded cluster method,in which the quantum clusters plus some ab initio ion model potentials were inserted in an array of point charges. On the surface, H₂CO₃ was dissociated into an H⁺ and an HCO ion. Among the CO₂ species, HCO was the only activated species on the surface. The results suggest that the reduction of CO₂ on Cu₂O (111) surface can start from the form of HCO. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A fragmentation study of dihydroquercetin using triple quadrupole mass spectrometry and its application for identification of dihydroflavonols in Citrus juices

A mass spectrometric method using electrospray ionization with triple quadrupole and quadrupole time‐of‐flight hybrid (Q‐Tof) mass spectrometry has been applied to the structural characterization of dihydroflavonols. This family of compounds has been studied by liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the first time in this work. A comprehensive study of the product ion MS spectra of the [M+H]⁺ ion of a commercially available standard has been performed. The most useful fragmentations in terms of structural identification are those that involve cleavage of the C‐ring, resulting in diagnostic ions of dihydroflavonol family: ^1,3A, ^1,2B, ^1,2B‐CO, ^0,2A, ^0,2A‐H₂O, ^0,2A‐CO, and ^0,2A‐H₂O‐CO, that allow the characterization of the substituents in the A‐ and B‐rings. In addition to those ions, other product ions due to losses of H₂O and CO molecules from the Y ion were observed. Their fragmentation mechanisms and ion structures have been proposed. The established fragmentation patterns have been used to successfully identity three dihydroflavonols found in tangerine juices for the first time. Copyright © 2009 John Wiley & Sons, Ltd.     

Theoretical study of spectroscopic constants and molecular properties of rare‐gas diatomic cations

Ab initio and density functional methods are applied to study the spectroscopic constants and molecular properties of the diatomic cations He, Ne, Ar, HeNe⁺, and HeAr⁺. Among these cations, HeAr⁺ is found to be weakly bound and its spectroscopic constants are calculated using the Lennard‐Jones potential. The other molecules that are strongly bound obey Morse potential, and their spectroscopic constants are calculated accordingly. The calculated spectroscopic constants agree very well with the theoretical and experimental values wherever available. Most of the spectroscopic constants and molecular properties are reported for the first time. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Spin probe mobility in relation to free volume and relaxation dynamics of glass‐formers: A series of spin probes in poly(isobutylene)

We present the dynamics of a series of three paramagnetic molecules of different volume, mass, and shape in amorphous glass‐forming polymer poly(isobutylene) (PIB) as investigated by means of electron spin resonance (ESR) technique. The reorientation behavior of spin probes is related to the ortho‐positronium (o‐Ps) annihilation in PIB from positron annihilation lifetime spectroscopy (PALS) and the extracted free volume information. It is also related to the dynamic data of PIB from broadband dielectric spectroscopy (BDS), neutron scattering (NS), and nuclear magnetic resonance (NMR) spectroscopy from literature. In the case of the smallest spin probe, 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO), a discontinuous course of the spectral parameter 2A_zz′ versus T dependence was observed and the subsequent phenomenological model‐free analyses of the spectral parameter, 2A_zz′ versus T, as well as of the correlation time, τ_c, versus 1/T plots provided the characteristic ESR temperatures ( , T_50G, ) and (T, T, T). These characteristic ESR temperatures were found to be consistent with the characteristic PALS temperatures: T, T = T from temperature dependences of the mean o‐Ps lifetime, τ₃, or the width of o‐Ps lifetime distribution, σ₃, respectively. In addition, the relationships between the spin probe size, V, and the free volume hole size distributions g_n(V_h) at the characteristic ESR temperatures indicate the significant influence of the free volume fluctuation at the crossover from slow to rapid regime as well as within the rapid motional regime. On the other hand, the two larger spin probes exhibit a rather continuous 2A_zz′–T plots with the respective T_50G's lying in the vicinity of T independently of their volume, mass and shape, suggesting the common origin of underlying process controlling this T_50G transition. Finally, these mutual PALS and ESR findings were compared with the known dynamic behavior of PIB which suggest that the dynamics of the TEMPO and the larger spin probes are related to free volume fluctuation associated with primary α ‐ and secondary β processes, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1058–1068, 2009     

Preparation of exfoliated polyacrylic clay nanocomposites with high loading: An investigation into the intercalation of ammonium‐terminated polyacrylic acid and polyacrylates

Low‐molecular‐weight polyacrylic acid with amine chain end used as a macromolecular intercalating agent was synthesized by radical polymerization using 2‐aminoethanethiol hydrochloride as chain transfer agent. Three polyacrylates (sodium polyacrylate‐t‐NH, calcium polyacrylate‐t‐NH, and zinc polyacrylate‐t‐NH) were prepared by neutralization from this polyacrylic acid using sodium hydroxide, zinc oxide, and calcium hydroxide as alkalies. The intercalation of ammonium‐terminated polyacrylic acid and polyacrylate was investigated by viscosity measurement, XRD, and TEM. Using this ammonium‐terminated polyacrylic acid as the intercalating agent, exfoliated polyacrylic acid/clay and polyacrylate/clay composites with a clay loading of ～30 and 20 wt %, respectively, were prepared through the evaporation of solvent from their clay suspensions. The thermal degradation of polyacrylic acid/clay and polyacrylate/clay composites was also studied by TGA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2335–2340, 2008     

Stable complex C2H4Al4Li3− and its similarity with bicyclo[2.2.0]hex‐2‐ene: A DFT study

We propose that complexation of all metal antiaromatic Al₄Li with C₂H₄ may lead to stable C₂H₄Al₄Li species [II(b)]. Complexation leads to the electron transfer from Al₄Li moiety to C₂H₄ and development of aromatic character in the Al₄ ring. Our proposed compound C₂H₄Al₄Li [II(b)] is very similar to the existing organic compound bicyclo[2.2.0]hex‐2‐ene [I(b)]. The complex C₂H₄Al₄Li [II(b)] can be imagined as an analogue of bicyclo[2.2.0]hex‐2‐ene [I(b)] achieved by a simple replacement of C₄H₄ in the later with π‐isoelectronic Al₄Li moiety in the former. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Laser ablation of ternary As‐S‐Se glasses and time‐of‐flight mass spectrometric study

Ternary chalcogenide As‐S‐Se glasses, important for optics, computers, material science and technological applications, are often made by pulsed laser deposition (PLD) technology but the plasma composition formed during the process is mostly unknown. Therefore, the formation of clusters in a plasma plume from different glasses was followed by laser desorption ionization (LDI) or laser ablation (LA) time‐of‐flight mass spectrometry (TOF MS) in positive and negative ion modes. The LA of glasses of different composition leads to the formation of a number of binary As_pS_q, As_pSe_r and ternary As_pS_qSe_r singly charged clusters. Series of clusters with the ratio As:chalcogen = 3:3 (As₃S, As₃S₂Se⁺, As₃SSe), 3:4 (As₃S, As₃S₃Se⁺, As₃S₂Se, As₃SSe, As₃Se), 3:1 (As₃S⁺, As₃Se⁺), and 3:2 (As₃S, As₃SSe⁺, As₃Se), formed from both bulk and PLD‐deposited nano‐layer glass, were detected. The stoichiometry of the As_pS_qSe_r clusters was determined via isotopic envelope analysis and computer modeling. The structure of the clusters is discussed. Copyright © 2009 John Wiley & Sons, Ltd.