Chemical Physics Letters (v.421, #4-6)

Coronavirus phylogeny based on triplets of nucleic acids bases by Bo Liao; Yanshu Liu; Renfa Li; Wen Zhu (313-318).
We considered the fully overlapping triplets of nucleotide bases and proposed a 2D graphical representation of protein sequences consisting of 20 amino acids and a stop code. Based on this 2D graphical representation, we outlined a new approach to analyze the phylogenetic relationships of coronaviruses by constructing a covariance matrix. The evolutionary distances are obtained through measuring the differences among the two-dimensional curves.

Theoretical study of sila-adamantane by Fabio Pichierri (319-323).
Density functional theory calculations have been carried out to characterize the ground-state electronic structure of the recently synthesized sila-adamantane cluster, Si14C24H72, which represents the smallest repeat unit of bulk silicon lattice [J. Fischer et al., Science 310 (2005) 825]. The computed HOMO–LUMO gap (∼4.5 eV) and ionization potential (∼6.4 eV) along with a negative value of the electron affinity indicate that the cluster is exceptionally stable against both oxidation and reduction. The chemical functionalization of this cluster (with –OH groups) and the encapsulation of small ions (Li+, Na+, and F) into its Si10 cage have also been computationally explored.

Electronic quenching of OH A2Σ+ radicals in collisions with molecular hydrogen by Ilana B. Pollack; Yuxiu Lei; Thomas A. Stephenson; Marsha I. Lester (324-328).
Collisional quenching of electronically excited OH A2Σ+ radicals by molecular hydrogen introduces nonradiative pathways that rapidly remove OH population from the excited state, and result in a significantly decreased fluorescence lifetime. One of these pathways is shown to lead to ground state OH X2Π products with ∼1 eV of internal excitation in both highly excited rotational levels of v  = 1 and the lowest rotational levels of v  = 2. This highly nonstatistical OH X2Π product distribution reflects the passage of the HO–H2 system through the conical intersection regions that couple the ground and excited state surfaces.

Vibrational relaxation of pure liquid water by Jörg Lindner; Peter Vöhringer; Maxim S. Pshenichnikov; Dan Cringus; Douwe A. Wiersma; Maxim Mostovoy (329-333).
Multicolor infrared ultrafast spectroscopy is applied to investigate the vibrational relaxation dynamics in liquid water at room temperature. In a sequence of experiments, both the stretching and the bending mode are photoexcited and probed. A unified model, capable of the reproduction of as much as 150 transients, yielded cross-sections and relaxation times for the stretching and bending modes. It is further demonstrated, that the energy from the initially excited stretching vibration is partitioned to the bending modes of approximately two water molecules.

1-NH proton of biotin is not always more active than 3-NH proton by Lei Zhang; Haoran Li; Xingbang Hu; Shijun Han (334-337).
Activity differences of the two amide protons of biotin were revisited via perspective from proton transfer in the gas phase, employing the B3LYP/6-31G methods. Our results reveal that for different conformation of biotin, the activity of the two amide is different: the 3-NH proton was more active than that of 1-NH for extended biotin, while less active for folded conformation, which indicated that the 1-NH proton of biotin is not always more active than the 3-NH proton. The results here may be helpful for realizing the mechanisms of activity differences of the two NH protons in solution.

Quantum teleportation in one-dimensional quantum dots system by Hefeng Wang; Sabre Kais (338-342).
We present a model of quantum teleportation protocol based on one-dimensional quantum dots system. Three quantum dots with three electrons are used to perform teleportation, the unknown qubit is encoded using one electron spin on quantum dot A, the other two dots B and C are coupled to form a mixed space-spin entangled state. By choosing the Hamiltonian for the mixed space-spin entangled system, we can filter the space (spin) entanglement to obtain pure spin (space) entanglement and after a Bell measurement, the unknown qubit is transferred to quantum dot B. Selecting an appropriate Hamiltonian for the quantum gate allows the spin-based information to be transformed into a charge-based information. The possibility of generalizing this model to N-electrons is discussed.

Contact angles of water and formamide droplets on a well-formed Sr5Cl(PO4)3 crystal with an aspect ratio of 3.2 were observed. The specific surface free energies of the ( 1 0 1 ¯ 0 ) and ( 1 0 1 ¯ 1 ) faces, calculated using the approximation of Fowkes, are 35 ± 2 and 61 ± 1 mN/m, respectively. The stability of the ( 1 0 1 ¯ 0 ) face corresponds to the morphology of this crystal, which tends to elongate in the 〈0 0 0 1〉 direction. The wide distribution of the measured contact angles is ascribed to the variation in the steps on the surface. An ideal flat surface without step should have uniform specific surface free energy, estimated to be γ ter  ⩽ 26 and ⩽50 mN/m for the ( 1 0 1 ¯ 0 ) and ( 1 0 1 ¯ 1 ) faces, respectively.

Laser burning of a gap in the spectrum of plasmon resonance of gold nanoparticles by P.V. Kazakevich; A.V. Simakin; G.A. Shafeev (348-350).
The effect of selective burning of a stationary gap in the spectrum of plasmon resonance of gold nanorods in the vicinity of laser wavelength is experimentally found. Formation of the gap is ascribed to the decrease of concentration of nanorods with certain aspect ratios that are in resonance with laser radiation.

We have observed emission from singlet and triplet exciplexes in electron donor (D)–acceptor (A) organic electroluminescent systems. The exciplex singlet-to-triplet fraction appears to be a function of electronic properties of the (D–A) complex molecular components and applied electric field. The fluorescence from exciplex singlets could be eliminated using a heavy atom (Gd)-substituted acceptor molecule allowing the efficient intersystem crossing of singlet into triplet exciplex states. By this a pure exciplex electrophosphorescent diode has been realized. These findings are of importance for the understanding of the exciplex formation mechanism and, thus, for material choice in device applications.

Quantitative cross-polarization NMR spectroscopy in uniformly 13C-labeled solids by Guangjin Hou; Feng Deng; Shangwu Ding; Riqiang Fu; Jun Yang; Chaohui Ye (356-360).
A novel QUantitative Cross Polarization (QUCP) scheme is proposed, which can be applicable for quantitative measurement of cross-polarization magic angle spinning (CP/MAS) spectroscopy in solid-state NMR. In this QUCP experiment, the combination of CP and broadband homonuclear recoupling technique (DARR) ‘homogenizes’ the non-uniform CP-prepared polarizations of dilute spins so that quantitative CP/MAS spectra can be obtained. Not only are all magnetizations enhanced uniformly by QUCP scheme, but also is the experimental time reduced greatly. In addition, the uniform enhancement is independent of the experimental parameters of cross-polarization. The present scheme is applicable for systems containing carbonyl, aromatic, and aliphatic carbons or some of these groups.

Structure and characterisation of [Pt(Me2pipdt)2][Pt(mnt)2]2 and its unusual magnetic properties associated with a non-regular one-dimensional [Pt(mnt)2] stack by Francesco Bigoli; Paola Deplano; Maria Laura Mercuri; Luciano Marchiò; Luca Pilia; Angela Serpe; Giorgio Concas; Francesco Congiu; Samuele Sanna (361-366).
For electro-oxidation of [Pt(Me2pipdt)2][Pt(mnt)2] (Me2pipdt= N,N′-dimethyl-piperazine-2,3-dithione; mnt = maleonitrile-2,3-dithiolate) (1a) the novel salt [Pt(Me2pipdt)2][Pt(mnt)2]2 (2a) has been prepared and characterised. 2a exhibits segregated chains of anionic and cationic complexes. The anions generate a non-regular stack with the separation between the planes of 3.558(5) Å [3.60(1) Å is the Pt⋯C=C(mid point) separation] and 3.643(5) Å [3.980(3) Å is the separation between Pt and S-atoms]. The cations are perpendicular to the anions and interposed between those stacks in a ribbon fashion. Magnetic measurements show the presence of a magnetic transition between the behaviour of an antiferromagnetic alternating-exchange chain and the behaviour of a set of antiferromagnetic dimers.

Thermosensitive aqueous solutions of polyvinylacetone by Wei-Tai Wu; Yusong Wang; Lei Shi; Qingren Zhu; Wenmin Pang; Guoyong Xu; Fei Lu (367-372).
The dimethylketals of poly(vinyl alcohol), termed polyvinylacetone (PVKA), of moderate ketalization degree in the range from 0.28 to 0.6 exhibited temperature-induced phase transition in aqueous solution, as revealed by cloud point measurements and electron micrographs, which was then further investigated on molecular level using solution-state 1H NMR measurements. The present phase transition is caused by the amphiphilic characteristics in the polymer chain. Moreover, this finding could be further applied as a novel strategy in the syntheses of thermosensitive polymer by the hydrophobic functionalities of linear polyol.

The novel immobilization technique using a poly(amino acid) multilayer was designed for the SPR sensing platform. These poly(amino acid) multilayer was confirmed as a relatively hydrophilic surface with little tendency for nonspecific adsorption of biomolecules and a flat surface that the biomolecular interactions can occur uniformly on the sensing surface. The poly(amino acid) multilayer functionalized with biotin was investigated to control the surface density and to estimate the optimum space between ligands for effective SPR sensing. This multilayer study demonstrates the importance of surface density which is significantly sensitive for fabrication of surface functional group in the monitoring of kinetic phenomena.

The electronic spectroscopy of transition metal carbonyls: The tough case of Cr(CO)6 by Nadia Ben Amor; Sebastien Villaume; Daniel Maynau; Chantal Daniel (378-382).
The electronic spectroscopy of Cr(CO)6, representative molecule for transition metal carbonyls is revisited by various quantum chemical methods from self consistent size consistent single double configuration interaction, equation of motion coupled cluster single double, multi state complete active space second-order perturbation, MS-CASPT2, and time-dependent density functional theory (TD-DFT). Comparison is done with previous CASPT2 and TD-DFT studies. Compared to experiment, most methods (except MS-CASPT2) do not give completely satisfactory quantitative results, which emphasizes the difficulty to perform highly accurate spectroscopy calculations. However, the results allow to clearly assign the nature of the different states, compared to experiment.

We investigate the performance for nuclear magnetic constant calculations for a selective set of density functional methods (B3LYP, PBE0, BLYP, PBEPBE, OLYP and OPBE). The testing set includes the 13C, 15N, 17O and 19F magnetic shieldings and chemical shifts of 23 molecules with 64 comparisons altogether. The results are compared and contrasted to the experimental gas phase data. We find that the OPBE exchange-correlation functional performs remarkably well for the whole set of the testing system, rendering OPBE the best GGA (generalized gradient approximation) functional, determined from energy criteria, for the prediction of nuclear magnetic constants.

The intermolecular potential of NO(A2Σ)–Ne: An ab initio study by Pedro Pajón-Suárez; Germán Rojas-Lorenzo; Jesús Rubayo-Soneira; Ramón Hernández-Lamoneda (389-394).
The intermolecular potential of the first Rydberg state of the NO–Ne system has been calculated using highly accurate ab initio calculations. The interaction is repulsive with extremely shallow van der Waals well depths (D e  < 4 cm−1) and long equilibrium intermolecular distances (R e  ∼ 6.5 Å ). In this region the potential is nearly isotropic but for shorter distances anisotropic terms become dominant favoring the linear approach of the neon atom to the nitrogen side of NO. An analytical representation has been constructed which should be useful for dynamical studies. Strong induced dipole effects are predicted for this system.

Comparison of p-type and n-type organic field-effect transistors using nickel coordination compounds by Tomohiro Taguchi; Hiroshi Wada; Takuya Kambayashi; Bunpei Noda; Masanao Goto; Takehiko Mori; Ken Ishikawa; Hideo Takezoe (395-398).
Organic field-effect transistors (OFETs) using metal complexes, bis(4-methyl-1,2-phenylenediamino) nickel (1) and bis(dithiobenzyl) nickel (2) were fabricated, and the transistor characteristics were measured in air and under vacuum. Compound 1 is a strong donor and oxidized at the redox potential of 0 V, while 2 is an acceptor and reduced to an anion around the same redox potential. Compound 1 shows p-type characteristics, whereas 2 exhibits n-type characteristics. Atmospheric oxygen increases both the ‘on’ and ‘off’ currents in p-type transistors of 1. The n-type characteristics of 2 are maintained in a few minutes in air, but degenerated in a few hours.

Synthesis of horizontally-aligned single-walled carbon nanotubes with controllable density on sapphire surface and polarized Raman spectroscopy by Hiroki Ago; Naoyasu Uehara; Ken-ichi Ikeda; Ryota Ohdo; Kazuhiro Nakamura; Masaharu Tsuji (399-403).
We report on the facile synthesis of aligned single-walled carbon nanotube (SWNT) arrays with controllable density on A-face sapphire substrates and the measurement of their polarized Raman spectra. The catalyst was prepared by simply dipping the sapphire substrate into a mixed solution of iron nitrate and molybdenum acetate, where Mo improved the nanotube yield as well as reproducibility. The angle dependence of the Raman spectra measured for the high-density nanotube array indicated the growth of SWNTs aligned mainly in the [ 1 1 ¯ 0 0 ] direction and two other directions. This suggests multiple mechanisms for the alignment, such as the pseudo one-dimensional Al arrangement and the presence of shallow grooves.

Electron-stimulated desorption of H, O and OH from thin films of sodium dihydrogenphosphate has been investigated in the range 0–19 eV. The yield functions exhibit a single broad peak with maxima at 8.8 ± 0.3 eV, 8.0 ± 0.3 eV, and 7.3 ± 0.3 eV, respectively, and a continuous rise above 15 eV. The structure is attributed to dissociative electron attachment causing scission of the O–H, P=O and P–O bonds, which is accompanied by the corresponding formation of the stable anions H, O and OH. From measurements of the time dependence of the anion signals, the effective cross-sections to damage the film near each peak energy are found to be 1.9, 1.7 and 0.9 × 10−15  cm2, respectively. The present results confirm previous conclusions on DNA damage induced by low energy electrons.

Thermodynamic properties of benzene adsorbed in activated carbons and multi-walled carbon nanotubes by Piotr A. Gauden; Artur P. Terzyk; Gerhard Rychlicki; Piotr Kowalczyk; Katarzyna Lota; Encarnacion Raymundo-Pinero; Elzbieta Frackowiak; François Béguin (409-414).
The efficiency of multi-walled carbon nanotubes (MWNTs) and traditional activated carbons for benzene adsorption is studied. Benzene adsorption isotherms and the related values of the calorimetric adsorption enthalpy at 298 K are used to calculate the entropy and the state of the adsorbed molecules. The analysis of the experimental data leads to the conclusion that both thermodynamic functions are related to the kind of porosity present in the studied materials. Our results also show that in the case of MWNTs the adsorption between the tubes is a very important effect which determines the mechanism of this process.

Accurate rate constant and quantum effects for N(2D) + H2 reaction by António J.C. Varandas; Tian-Shu Chu; Ke-Li Han; Pedro J.S.B. Caridade (415-420).
We report accurate close coupling quantum wave packet calculations of the rate constant for the reaction N(2D) + H2  → NH + H using a recently reported single-sheeted double many-body expansion potential energy surface for NH2(12A″) that has been calibrated from high level ab initio MRCI energies. Results from quasi-classical trajectories run on the same potential energy surface are also given, and used to rationalize the quantum ones. The calculated rotationally averaged rate constant is found to be in good agreement with experimental data. A comparison with other theoretical results is also presented.

High-resolution infrared spectra of Ne–12C18O2 and Xe–12C18O2 have been observed in the ν 3 band (2314 cm−1) region of 12C18O2 by diode laser absorption spectroscopy of a pulsed molecular beam. The vibrational band origins and rotational constants for these complexes are obtained. The observed shifts of the ν 3 band origin for Rg–CO2 (Rg = Ne, Ar, Kr, Xe) with respect to that of CO2 exhibit a systematic 16O–18O isotope effect excepting a significant deviation for Ne–CO2 from a regular trend. This apparent anomaly is interpreted in terms of a change in the intramolecular potential function of CO2 caused by complex formation.

Quantum calculations are performed for an anion water cluster representing the first hydration shell of the solvated electron in solution. The absorption spectra from the ground state, the instant excited states and the relaxed excited states are calculated including CI-SD interactions. Analytic expressions for the nonadiabatic relaxation are presented. It is shown that the 50 fs dynamics recently observed after s → p excitation is best accounted for if it is identified with the internal conversion, preceded by an adiabatic relaxation within the excited p state. In addition, transient absorptions found in the infrared are qualitatively reproduced by these calculations.

Molecular oxygen adsorption on electropositive nano gold tips by F. Tielens; J. Andrés; T.-D. Chau; T. Visart de Bocarmé; N. Kruse; P. Geerlings (433-438).
The effect of atom coordination and influence of an external electrostatic field on binding and dissociation energies of molecular oxygen on a nano modified Au surfaces are investigated. Weak O and O2 adsorption are found in our models. A considerable decrease of the dissociation energy of O2 was found when adsorbed on small gold clusters or gold pyramids. It is concluded that in the presence of an electric field no dissociation of O2 will occur in our model. This result is in agreement with field ion microscopy (FIM) and field electron microscopy (FEM) experiments, where no dissociation of O2 is encountered.

The stopping power of electrons in methane based tissue equivalent materials is reported in this study for incident energies from 10 to 10 000 eV. These results have been obtained from the calculated integral inelastic cross-sections in combination with an average excitation energy derived from the experimental energy loss spectra. The reliability of the present calculated cross-section data has been checked by comparison with the electron scattering total cross-sections measured in a transmission beam experiment. Some discrepancies, on the order of 25%, with the calculated stopping powers available in the literature are discussed.

Stability and properties of planar carbon clusters by Shu-hong Xu; Ming-yu Zhang; Yuan-yuan Zhao; Bao-guo Chen; Jian Zhang; Chia-Chung Sun (444-447).
A series of annular structures of C n (3 ⩽  n  ⩽ 31) are optimized at DFT/B3LYP/6-31G theoretical level. The calculated results show that odd structures and even structures have different bonding characters and properties. NBO analyses indict that C6, C10, C14, C18, C22, C26 and C30 molecules have two big delocalized π-bonding and C8, C12, C16, C20, C24 and C28 molecules have only one big delocalized π-bonding. C4 has aromaticity for it has different conformation which makes it have special bonding character. In addition, linear C n structures are calculated to further investigate the nature of annular C n structures.

O2 adsorption on small neutral, anionic and cationic silver clusters Ag n (n  = 1–7) has been studied by using the PW91PW91 density functional method. The adsorption energies of O2 on the anionic and neutral clusters have an odd–even alternation pattern clearly, and our calculations give the same adsorption behavior of O2 on silver cluster anions as the experimental measurements. The adsorption energies on the cationic clusters, instead, are generally smaller than those on the anionic and neutral clusters, and reach a local maximum at Ag 4 O 2 + . Natural bond orbital analyses show that electrons mostly transfer from silver atoms to molecular O2 except for the smallest silver cluster cations (n  = 1–3).

Ab initio study of the H + ClONO2 reaction by Xiaofang Chen; Xin Zhang; Keli Han; António J.C. Varandas (453-459).
The mechanism of the H + ClONO2 reaction is examined by performing QCISD calculations at geometries optimized at the MP2 level. Each of the six reaction channels involves stereoisomeric transition states that have identical energy barriers. The lowest energy barrier is 24.2 kcal mol−1 for the indirect metathetical pathway leading to OH +  cis-ClONO, being the corresponding rate constant calculated employing TST theory. The NO2-elimination channel and the indirect metathetical pathway leading to OH +  trans-ClONO should compete with each other as they have barriers of 24.8 and 25.1 kcal mol−1. For Cl-substitution, Cl-abstraction, and N-attack, the barriers are 27.4, 35.1, and 41.3 kcal mol−1.

The bond polarizabilities of 2-aminopyridine are obtained from the Raman intensities by an algorithm proposed by Wu et al. [B. Tian, G. Wu, G. Liu, J. Chem. Phys. 87 (1987) 7300]. Their contrast to the bond electron densities by RHF/6-31G shows clues to the electronic structures of its Raman excited virtual states. The differentiations by 514.5 and 632.8 nm excitations are stressed to show the flowing out of the electronic charges from the C–C bonds to the C–N bonds and toward the peripheral C–H and N–H bonds in the virtual states.

Linear free-energy relationship by O.A. Khakhel’ (464-468).
It is shown that a nature of the LFER phenomenon is related to phase volumes of the system’s states, for which a difference of free energy is determined. An invariability of these volumes is the single factor generating the LFER phenomenon. As an example, the LFER manifestations for an intramolecular excimer formation with 1,3-di(1pyrenyl)propane in various solvents are analyzed.

Control the chirality of carbon nanotubes by epitaxial growth by Stephanie Reich; Lan Li; John Robertson (469-472).
We propose an idea for the chirality-selective growth of nanotubes by controlling the type of caps that form on the catalyst at the nucleation stage. Particular caps could be favored by their epitaxial relationship to the solid catalyst surface and the corresponding tubes grow preferentially. We show by ab initio calculations that lattice-matched caps and tubes are more stable next to a Ni surface than non-lattice-matched structures. This explains the dominance of certain chiralities in samples grown by low-temperature chemical vapor deposition.

Using the scanning tunneling microscope (STM) at 5 K, we have observed spontaneous formation of clusters between CO molecules adsorbed on the Au(1 1 1) surface. In all the (CO) n clusters (n  = 2–5), the CO molecules are bonded to the nearest-neighbor gold atoms in characteristic arrangements. The CO dimer was found to exhibit an unusual tip-induced motion, where one molecule orbits around its neighbor. The clusters could be translated and manipulated without decomposition using the STM tip. These results demonstrate that the interaction between CO molecules bonded in particular cluster geometries to the nearest-neighbor Au atoms is attractive rather than repulsive as commonly assumed.

The orientation of bistable molecules incorporated in a polymer host is addressed and studied by means of all-optical poling. Molecular reorientation between two stable molecular forms is assigned as the origin of the optically induced second-order nonlinear optical susceptibility. We found a new non-photochromic photo-induced reaction scheme by which efficient all-optical poling is achieved.

Hybrid-density functional study of magnetism and ligand control in Ni9 complexes by Mitsuo Shoji; Kenichi Koizumi; Tomohiro Hamamoto; Yasutaka Kitagawa; Shusuke Yamanaka; Mitsutaka Okumura; Kizashi Yamaguchi (483-487).
Strong influences of bridging ligands L on the magnetism of two Ni9 complexes, Ni9L2(O2CMe)8 {(2-py)2CO2}4 (L=OH 1 and N 3 - 2) are demonstrated by magnetic interactions. Effective exchange integrals J for 1 and 2 are determined non-empirically using UB3LYP and UBLYP. The calculated magnetic susceptibility for 1 is wholly consistent with the experimental values. Although the ground spin state of 2 obtained using the calculated J values agrees with the experimental S  = 9 state, fitting of the J values to the experimental magnetic susceptibility curve indicates weak antiferromagnetic interactions via the azido ligands.

The IR active cis-bending vibrations of the linear carbon chains C2n (n  = 2–5) in their 3 Σ g - electronic ground states have been studied by means of coupled cluster calculations with large basis sets. All four molecules investigated have rather steep and almost quadratic cis-bending potentials and are thus likely to behave like fairly normal semi-rigid molecules. Harmonic cis-bending vibrational wavenumbers and the corresponding absolute IR intensities were calculated for all four species. Very good agreement with argon matrix IR spectroscopy is obtained for linear C4 and the present calculations support the assignment of an astronomical feature at 57.5 μm (174 cm−1) to this molecule.

Dielectric properties of oil–water complexes using terahertz transmission spectroscopy by Stefan Gorenflo; Ulrike Tauer; Iliyana Hinkov; Armin Lambrecht; Richard Buchner; Hanspeter Helm (494-498).
Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the water content in synthetic oils. For this purpose, water was added to polyglycol oils, which are able to dissolve a certain percentage of water. Applying THz-TDS, changes in the absorption coefficient and refractive index are observed and characterized. Comparison of the experimental data with predictions based on Beer–Lambert and Lorentz–Lorenz-theory, respectively, exhibits excellent agreement and clearly indicates that water is not dissolved in form of clusters but rather via hydrogen-bonded oil–water complexes.

We report reduced dimensionality quantum mechanical calculations of the rate constants of the Mu + CH4  → MuH + CH3 reaction. An ab initio potential energy surface is developed to describe the reactive process in a two-dimensional space and incorporates the zero-point energy of the spectator modes using the CCSD(T, full)/cc-pVTZ//MP2(full)/cc-pVTZ method. Scattering calculations produced reaction probabilities and total rate constants. MuH products are formed mainly in their ground vibrational state. Reaction from the first stretch excited state of CH4(s  = 1) is found to be more important than that from CH4(s  = 0) ground state. Rate constants exhibit pronounced quantum tunneling in the considered temperature range [200–2000 K] and a reasonable comparison is noticed with experiment.

S–H bond dissociation enthalpies: The importance of a complete basis set approach by P. Cabral do Couto; Benedito J. Costa Cabral; José A. Martinho Simões (504-507).
The S–H homolytic bond dissociation enthalpies (BDEs) for several compounds of reference were estimated by different theoretical methods including CCSD(T), CBS-QB3, and the multi-coefficient extrapolated density functional theory multi-level approaches, MCG3-MPWB and MCG3-TS. Emphasis was placed on the importance of extrapolating theoretical BDEs to complete basis set. A very good agreement between S–H BDEs from CCSD(T) calculations and experiment is observed when a simple dual extrapolation scheme to complete basis set proposed by Truhlar is adopted. For thiophenol, our CCSD(T) estimate for the S–H BDE (347.2 kJ mol−1) supports a recent experimental value obtained from time-resolved photoacoustic calorimetry (349 ± 5 kJ mol−1).

Rotational and translational diffusions of fluorescent probes during gelation process by Yusuke Hattori; Pascal Panizza; Louis Letamendia; Hideharu Ushiki (508-512).
Gelation process has been investigated by using light scattering techniques in recent years. We measured both of rotational and translational motions of fluorescent probes during gelation process. The measurements were performed after the temperature quenched at 30 °C. As the results, rotational diffusion coefficient of fluorescein was decreased after 6.0 × 104  s and energy transfer rate was reduced after 2.0 × 104  s. We sorted the gelation process into the following three parts, (I) pre-gelation, (II) reduction of translational diffusion (aging), and (III) reduction of rotational diffusion with saturating translational diffusion (post-gelation). The time scale of the process was completely different from the results of other methods.

NMR study of water adsorption in single-walled carbon nanotubes by Shenghua Mao; Alfred Kleinhammes; Yue Wu (513-517).
1H nuclear magnetic resonance was used to measure water adsorption isotherms at room temperature in cut single-walled carbon nanotubes (SWNTs) and activated carbon (AC). Although the level of water adsorption inside SWNTs is as high as in any AC, the adsorption isotherm reveals the lack of wetting inside cut-SWNTs. Quantitative analysis and various effects of adsorbed D2O on gas adsorption inside cut-SWNTs indicate that adsorbed water molecules reside mostly near principal adsorption sites associated with tube ends and defects.

Evidence for exciton fission and fusion in a covalently linked tetracene dimer by Astrid M. Müller; Yuri S. Avlasevich; Klaus Müllen; Christopher J. Bardeen (518-522).
A photophysical study of the covalently linked tetracene dimer 1,4-bis(tetracen-5-yl)benzene is presented. While the dimer’s steady state spectroscopy is similar to that of monomeric tetracene, it also exhibits a long-lived fluorescence signal in solution and solid polyethylene films, which is absent in the monomer. The behavior of this long-lived component as a function of temperature and oxygenation provides evidence that a small (<1%) fraction of the singlet excited states undergoes fission into two triplet states, which recombine on the order of 100 ns. A kinetic model based on this mechanism fits the fluorescence decay data quantitatively.

Enhancement of Raman modes by coherent control in β-carotene by Jürgen Hauer; Hrvoje Skenderovic; Karl-Ludwig Kompa; Marcus Motzkus (523-528).
The enhancement of vibrational modes by phase-shaped femtosecond laser pulses is studied under resonant and non-resonant conditions in an open loop coherent control experiment using non-linear Raman spectroscopy. Applying multipulse sequences matching the periodicity of single vibrations, the modes of β-carotene solvated in cylcohexane were not only specifically excited, but under resonant conditions also enhanced compared to the Fourier-limited case. This effect is attributed to an increased population transfer to the excited state and stronger coherences created and demonstrates the feasibility to selectively amplify ground state Raman modes by coherent control.

The use of hyperbolic secant, HS, pulses to obtain NMR signal enhancements for the central transition of spin-5/2 quadrupolar nuclei in solids is explored. By inverting the populations of nuclear-spin energy levels prior to applying a selective-observe pulse, enhancements near the theoretical maximum are obtained for the central 27Al NMR transition in a single crystal of α-Al2O3. The experimental enhancements obtained using HS inversion pulses for powder samples are compared to those obtained using the double-frequency sweep method. For every sample investigated, the HS enhancement factors are equal to or superior to those previously reported using other enhancement techniques.

Electronic properties of Cs-atom doped aluminum and silicon clusters: Al n Cs m and Si n Cs m by Kiichirou Koyasu; Minoru Akutsu; Junko Atobe; Masaaki Mitsui; Atsushi Nakajima (534-539).
The effect of Cs atom doping on metallic aluminum clusters and covalent silicon clusters, Al n Cs m (n  = 5–14, m  = 0–3) and Si n Cs m (n  = 5–16, m  = 0–3), was examined by mass spectrometry and anion photoelectron spectroscopy. For clusters containing Cs atom(s), the electron affinities of both clusters are generally decreased and the following characteristic features are observed: for Al n Cs m , Cs-atom doping causes (1) electron filling into the electronic shell structure of the Al n clusters and (2) geometrical packing of icosahedral 13-atoms, while for Si n Cs m Cs-atom doping enhances electronic stability to be ascribed to pure Si n clusters, particularly at (n,  m) = (10, 3) and (13, 1).

DFT functionals and molecular geometries by K.M. Flurchick (540-543).
This note describes a procedure to evaluate the differences between molecular geometry for some commonly used DFT functionals. This approach aids in identifying the ability of the different functionals to determine molecular structural properties, such as bond lengths and bond angles. The approach is applied to a simple set of molecules with single, double and triple bonds.

Nonlinear magnetic susceptibility of ferrofluids by G. Wang; J.P. Huang (544-548).
In ferrofluids, external magnetic fields can produce a nonlinearity in the dependence of magnetic susceptibilities on the field strength, due to both normal saturation and abnormal saturation. We derive the nonlinear magnetic susceptibility by using a Langevin model. Then, we investigate the nonlinear ac responses of the magnetic susceptibility by means of a perturbation expansion method and an orthogonal numerical method. The two methods are numerically shown in excellent agreement. We find that the responses are sensitive to suspension structures and field frequencies. Thus, by detecting the ac responses, it seems possible to real-time-monitor the structure of ferrofluids.

A total of ∼700 trajectories have been calculated for the title reaction using the direct ab initio molecular dynamics method at the RMP2(full)/cc-pVDZ level with the microcanonical sampling technique for the initial condition. It was found that the current result for product energy and state distributions is similar to the previous one obtained at the same level of theory [Y. Kurosaki, K. Yokoyama, J. Phys. Chem. A 106 (2002) 11415]. This is because in this reaction there is a substantial coupling between the reaction coordinate and another degree of freedom on the way from transition state to products.

Organic field-effect transistors were fabricated where the active semiconductor layer consisted of a co-evaporated film of pentacene and a perylene derivative, N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide. The device characteristics were evaluated in an oxygen-free environment. The field-effect transistor showed excellent ambipolar operation with field-effect hole mobility of 0.09 cm2  V−1  s−1 and field-effect electron mobility of 9.3 × 10−3  cm2  V−1  s−1. The threshold voltage for p-channel operation was −18 V and the same for n-channel operation was 15 V. This ambipolar device could be a building block to form flexible integrated circuits with low-power consumption and ease of design.

Heat capacity of nanoporous crystal, 12CaO · 7Al2O3 (C12A7), was measured between 85 mK and 5 K under magnetic field up to 9 T. The heat capacity under zero magnetic field did not fit to the T 3 law; the deviation was discussed in terms of the disorder of the O2− ions in the subnanometer-sized cages in C12A7 lattice. Under magnetic field, the heat capacity showed a Schottky-type anomaly due to the Zeeman splitting of O and O 2 - radicals (S  = 1/2) incorporated in the cages. The total concentration of O and O 2 - radicals in the crystal was estimated to be 4.4 × 1018  cm−3 (2.3 × 1021  mol−1, 3.8 × 10−3  mol mol−1).

A coupled-cluster study of the HOSO and HSO2 radicals by Brian Napolion; John D. Watts (562-565).
CCSD(T) calculations with triple-zeta valence plus polarization basis sets have been performed on HOSO and HSO2 to determine structures, vibrational frequencies, and infrared intensities for the first time with coupled-cluster methods. It is found that the planarity of HOSO is very sensitive to basis set. The calculated frequencies and intensities offer further support for the identification of HOSO and HSO2 in rare gas matrices.

The full non-rigid group of hexamethylbenzene using wreath product by Mohammad Reza Darafsheh; Ali Reza Ashrafi; Arash Darafsheh (566-570).
The character table of the non-rigid hexamethylbenzene, C6(CH3)6, is derived for the first time. The group of all feasible permutations is the wreath product group D6[Z3] = Z3  ∼ D6 and it consists of 8748 operations divided into 174 conjugacy classes and irreducible representations. We have shown that the full character table can be constructed using elegant matrix type generator algebra. The group can also be useful for weakly-bound (NH3)6.

Measurement of magnetic field effects on radical recombination reactions using triplet–triplet energy transfer by K.B. Henbest; K. Maeda; E. Athanassiades; P.J. Hore; C.R. Timmel (571-576).
Previously, the effect of applied magnetic fields on the yield of the reaction of the radical ions of pyrene and 1,3-dicyanobenzene (DCB) has been measured by monitoring the emission of the pyrene/1,3-DCB exciplex formed from the singlet state of the spin-correlated radical pair (SCRP). This Letter describes an alternative approach that relies on energy transfer from the excited triplet state of pyrene to the tris(2,2′-bipyridyl)ruthenium(II) ion, Ru ( bpy ) 3 2 + , allowing the recombination of the triplet SCRP to be monitored by emission spectroscopy. Measurements of magnetic field effects in combination with time-resolved flash photolysis and luminescence experiments confirm triplet–triplet energy transfer as the reaction mechanism.

Simulation of the life cycle of adsorbate islands on the Pt(1 0 0) surface during the NO + NH3 reaction by Matías Rafti; José Luis Vicente; Hannes Uecker; Ronald Imbihl (577-583).
Photoemission electron microscopy (PEEM) of the NO + NH3 reaction on a Pt(1 0 0) single crystal surface under UHV conditions reveals complicated dynamical behavior. As a rationalization for the observed spatio-temporal evolution of the surface a so-called ‘island growth mechanism’ was proposed. Here, we present the results of 1D simulations with a realistic 7-variable model that takes explicitly into account macroscopic surface defects on the catalyst. Depending on whether or not we consider site-blocking effects of coadsorbates on diffusing species, we obtain different patterns. The experimental PEEM data can be qualitatively reproduced in this way.

Large-scale synthesis of carbon spheres by reduction of supercritical CO2 with metallic calcium by Zhengsong Lou; Changle Chen; Dejian Zhao; Shengli Luo; Zhongchun Li (584-588).
Carbon spheres with approximate uniform diameters of about 1–2 μm were synthesized by chemical reduction of supercritical CO2 with metallic calcium at 550 °C. The products were characterized by techniques including XRD, scanning electron microscope, Raman, and transmission electron microscopy. The formation mechanism was thought to be as follows: the thermal movement of carbon nano-granules on the surface of metallic calcium leads to the formation of carbon spheres, which was confirmed by reference experiments at different temperatures. What is more, the formation mechanism of carbon sphere in supercritical CO2 system was discussed.

The unimolecular dissociation of methanethiol cation (CH3SH+, 1) has been investigated theoretically. Ab initio and Gaussian-2 theory calculations have been performed to obtain the potential energy surface (PES) for loss of H and H2 from 1. On the basis of the PES obtained, the relative abundances of the two channels near threshold have been calculated by Rice–Ramsperger–Kassel–Marcus modeling. The calculated result agrees with the previous experimental one, suggesting that the dissociation occurs statistically near threshold on the ground electronic state.

Calculated BeH2 bond distances are re-interpreted in the light of the corrected experimental equilibrium bond distance. In addition values for BeH are given.

Author Index (597-607).