Chemical Physics Letters (v.368, #3-4)
Editorial Board (IFC).
Hydrogen absorption and magnetic moment of Ni n clusters by C Ashman; S.N Khanna; M.R Pederson (257-261).
Theoretical studies to investigate the effect of H absorption on the magnetic moment of small Ni n clusters have been carried out using gradient corrected density functional approach. Our studies on clusters containing up to 4 Ni and 2 H atoms show that the successive addition of H atoms to Ni n clusters leads to an oscillatory change in the magnetic moment. Electronic structure analysis shows that, in most cases, the changes in the magnetic moment can be related to the relative position of the majority and minority lowest unoccupied molecular orbital of the preceding cluster. Ni2H2 is found to be marked by energetically close isomers with spin singlet and triplet multiplicities.
Conformation-dependent ionization of l-phenylalanine: structures and energetics of cationic conformers by Kang Taek Lee; Jiha Sung; Kwang Jun Lee; Seong Keun Kim; Young Dong Park (262-268).
The vertical ionization energy of l-phenylalanine was found to depend uniquely on the type of intramolecular hydrogen bonding in the neutral conformers. Between the two known subgroups of conformers, the ionization energy of those with a large backbone–residue interaction through a π-hydrogen bond was considerably higher than the others because of the repulsion between the backbone and the residue in the cation. It was strongly noted from this study and others in the past that the neutral conformation uniquely determines such disparate properties as the cationic structure, the magnitude of the ionization energy, and the propensity toward hydration.
Lattice vibration and absorbance of Er:Yb:YCOB single crystals by Gui-Wu Lu; Chun-Xi Li; Wen-Chuan Wang; Zi-Hao Wang; Hai-Rui Xia; Huai-Jin Zhang; Xian-Lin Meng; Li-Xia Li (269-275).
Er3+- and Yb3+-doped yttrium calcium oxoborate Er:Yb:YCa4O(BO3)3 (Er:Yb:YCOB) crystallizes with a fluorapatite-type structure in the monoclinic system. Its lattice vibrational modes were calculated by using space group theory, and Raman spectra were measured at room temperature with different scattering geometry projects. The experiments show that the characteristic lattice vibrational modes of Er:Yb:YCOB crystal arise mainly from the internal vibrations of the BO 3, CaO 6 , and YO6 groups. The three-dimensional network structure of Er:Yb:YCOB crystal is identified, and its excellent nonlinear optical (NLO) properties are mainly attributed to the BO3 clusters that connects all the distorted YO6 and CaO6 octahedral clusters together. The combination of the strong absorption at 976 nm and the strong emission at 1537 nm makes this material very promising for use in an infrared laser system.
A curious regularity in the dissociative photoionization of fluorinated benzenes: why do C6F6 + and C6H6 + dissociate so differently? by T. Kinugawa; A.M. Hodgekins; J.H.D. Eland (276-281).
Photoelectron-photoion coincidence (PEPICO) spectra at 73.6 nm reveal an interesting fact; from hexafluorobenzene cation the C5F3 + fragment is most abundant whilst from the benzene cation C4H4 + is far more abundant than C5H3 +. These contrasting results are connected, as shown by the PEPICO spectra of other fluorinated benzenes, by a regular change of the dominant fragment from C5F3 + to C4H4 + as the number of fluorine atoms decreases. This regularity is consistent with the appearance energies, at QCISD[T] or CBS-QB3 levels, of C5F m H3−m + in the acetylene-cyclopropene structure and C4F n H4−n + in the methylene-cyclopropene and/or the vinyl-acetylene structures. The energy-selected PEPICO data further support the theoretical results.
Laser controlled molecular switches and transistors by Jörg Lehmann; Sébastien Camalet; Sigmund Kohler; Peter Hänggi (282-288).
We investigate the possibility of optical current control through single molecules which are weakly coupled to leads. A master equation approach for the transport through a molecule is combined with a Floquet theory for the time-dependent molecule. This yields an efficient numerical approach to the evaluation of the current through time-dependent nano-structures in the presence of a finite external voltage. We propose tunable optical current switching in two- and three-terminal molecular electronic devices driven by properly adjusted laser fields, i.e., a novel class of molecular transistors.
Quantum dressed classical mechanics: application to the photo-absorption of pyrazine by Cecilia Coletti; Gert D. Billing (289-298).
A newly formulated theory for treating time-dependent molecular quantum dynamics has been used to calculate the photo-absorption spectrum of pyrazine. Comparison with quantum mechanical results shows an excellent agreement during the whole propagation, proving that the present approach, when used in a discrete variable representation scheme, converges to exact quantum results if enough grid points are used. The addition of an increasing number of bath modes to the basic four mode model is also investigated and the performance of the method discussed.
Clean double-walled carbon nanotubes synthesized by CVD by W.Z. Li; J.G. Wen; M. Sennett; Z.F. Ren (299-306).
High quality double-walled carbon nanotubes (DWNTs) were synthesized by decomposition of methane over cobalt (Co) nanoparticles supported on porous MgO nanoparticles. The growth was significantly influenced by catalyst concentration and MgO type. Catalysts with 2.5–5 wt% Co loaded MgO (pore size: ∼4 nm) efficiently grow DWNTs with diameters of 2–4 nm, high graphitization, clean surfaces, and clean inside channels. The preliminary separation of DWNTs from MgO, Co and other carbonaceous nanoparticles has been carried out. Energy dispersive X-ray spectroscopy and X-ray diffraction were employed to analyze the chemical composition of the materials before and after purification.
Nonlinear optics of hexaphenyl nanofibers by F. Balzer; K. Al Shamery; R. Neuendorf; H.-G. Rubahn (307-312).
The nonlinear optical response of films of needle-shaped para-hexaphenyl nanoaggregates on mica surfaces is investigated. Two-photon luminescence as well as optical second harmonic generation (SHG) are observed following excitation with femtosecond pulses at 770 nm. Polarization dependent measurements reveal that the nonlinear optical transition dipole moment is oriented with an angle of 75° with respect to the needles long axes. The absolute value of the macroscopic second-order susceptibility, averaged over a size distribution of p-6P nanoaggregates, is estimated to be of the order of 6×10−10 esu.
A DFT study of synthesis of acetic acid from methane and carbon dioxide by Jian-guo Wang; Chang-jun Liu; Yue-ping Zhang; Baldur Eliasson (313-318).
We have previously reported an experimental investigation on synthesis of acetic acid directly from CH4 and CO2 via dielectric-barrier discharge. In this work, a DFT study was conducted using three hybrid DFT methods in order to understand the mechanism of such direct synthesis. It suggests that the synthesis is via two pathways with CO2 − and CO as key intermediates. The energy requirement with CO2 − pathway is much less than that with CO. The methyl radical formation and the dissociation of CO2 are two limiting steps for the synthesis of acetic acid directly from CH4 and CO2.
Calculation of band gaps in molecular crystals using hybrid functional theory by W.F Perger (319-323).
Hybrid functional theory is applied for calculation of band gaps in the molecular crystals anthracene, pentaerythritol (PE), pentaerythritol tetranitrate (PETN), and cyclotrimethylene trinitramine (RDX). The B3LYP hybrid functional is observed to produce band gap estimates in reasonable agreement with experiment for anthracene and RDX. This approach, which has been successfully used recently for other materials, is efficient and practical, which is especially important for these large molecular crystals.
The correlation between I(2 P 3/2)/I(2 P 1/2) branching and CH3 rotation in photolysis of single quantum state-selected CH 3 I (JK=11) by Alrik J van den Brom; M Laura Lipciuc; Maurice H.M Janssen (324-330).
The dependence of the I(2 P 3/2)/I(2 P 1/2) branching ratio on the end-over-end rotational state of the methyl photofragment, CH 3 (ν2=2|N,K=1), after photodissociation at 266 nm of single quantum state-selected CH 3 I (JK=11) molecules is reported. Using velocity map imaging the spatial velocity distribution of the vibrationally excited CH3 (ν 2=2) photofragment was detected. The I(2 P 3/2) and I(2 P 1/2) yields were extracted from the speed distribution of rotationally selected CH 3 (ν2=2|N,K=1) photofragments. Quantitative analysis shows a strongly increasing I(2 P 3/2)/I(2 P 1/2) branching ratio with increasing CH3 end-over-end rotational motion, in reasonable agreement with recent three-dimensional state-to-state ab initio calculations.
Fabrication of inorganic molybdenum disulfide fullerenes by arc in water by Noriaki Sano; Haolan Wang; Manish Chhowalla; Ioannis Alexandrou; Gehan A.J. Amaratunga; Masakazu Naito; Tatsuo Kanki (331-337).
Closed caged fullerene-like molybdenum disulfide (MoS2) nano-particles were obtained via an arc discharge between a graphite cathode and a molybdenum anode filled with microscopic MoS2 powder submerged in de-ionized water. A statistical study of over 150 polyhedral fullerene-like MoS2 nano-particles in plan view transmission electron microscopy revealed that the majority consisted of 2–3 layers with diameters of 5–15 nm. We show that the nano-particles are formed by seamless folding of MoS2 sheets. A model based on the agglomeration of MoS2 fragments over an extreme temperature gradient around a plasma ball in water is proposed to explain the formation of nano-particles.
Long time tail effect in liquid state NMR spectroscopy by Shangwu Ding; Pin-Hsiu Liu; Yu-Wen Hong (338-345).
Experimental evidence of long time tail effect in liquid state NMR spectroscopy has been observed, characterized and its potential applications proposed. It is found that the physical mechanism for the long time tail of the spin auto-correlation function in the liquid state is similar to, but not identical with, that in the solid state. The net effect is shown that the decaying function t −d ′/2 where d ′<d (the dimension of the spin network), which is clearly more desirable for its applications. Particularly significant to the applications to the enhancement of resolution is that decaying slower than t −d/2 can be achieved, indicating better resolution improvement can be achieved than in the solid state. Extensive exposure of the characteristics of this phenomenon is provided with a number of model compounds and tentative theoretical analysis is given.
A coarse-grained model for particle dynamics simulations of complex fluids by Chee Chin Liew; Masuhiro Mikami (346-351).
We have devised a ‘soft-attractive-and-repulsive’ pair-potential model, which has a hardness parameter (β) besides energy and length parameters, to adopt three coarse-graining procedures for soft-matter. Namely, (i) Grouping for a monomer or segment; (ii) Packing for a group of molecules; and (iii) Time-averaging to take account of effective potential over a time-span. The resulting models are capable of reproducing liquid–vapor coexistence curves of real fluids at various coarse-grained levels. A model with β=3.0 is analytically representing a time-averaged effective potential over a long time-span. Its combination with Dissipative Particle Dynamics method allows us to reproduce dynamic properties for complex fluids.
Optical nonlinearities of space selectively precipitated Au nanoparticles inside glasses by Shiliang Qu; Chongjun Zhao; Xiongwei Jiang; Guangyu Fang; Yachen Gao; Huidan Zeng; Yinglin Song; Jianrong Qiu; Congshan Zhu; K. Hirao (352-358).
Optical nonlinearities of Au nanoparticles precipitated inside glasses induced by irradiation of a focused femtosecond laser were investigated using Z-scan technique with 8 ns pulses at 532 nm. The transformation behaviors both from self-defocusing to self-focusing and from saturable absorption to reverse saturable absorption were observed in the glass samples, which depend drastically on the irradiation power density of the femtosecond laser used. The optical nonlinearities were analyzed in detail and proved numerically by the excited-state theory of conduction band electrons.
The orientational behaviour of 1,4-difluorobenzene and p-benzoquinone in ZLI1132 and EBBA nematic solvents by Giorgio Celebre; Giuseppina De Luca (359-364).
The non-polar rigid molecules 1,4-difluorobenzene and p-benzoquinone dissolved in ZLI1132 and EBBA nematic solvents show a bizarre ‘double face’ rod-like or disk-like orientational behaviour, depending on the used solvent. In the present Letter it is shown that the observed effect, unpredictable on the basis of solely short-range orientating mechanisms, can be qualitatively accounted when also electrostatic long-range interactions are taken into account (in particular, the coupling between the solute quadrupole moment and the solvent electric field gradient). The obtained result confirms the non-negligible role played by electrostatic interactions, even in the case of non-polar molecules.
Properties of chrysene in the higher triplet excited state by Xichen Cai; Michihiro Hara; Kiyohiko Kawai; Sachiko Tojo; Tetsuro Majima (365-369).
Properties of chrysene in the higher triplet excited state were studied by the two-color two-laser flash photolysis method. Triplet energy transfers from chrysene in the higher triplet excited state to quenchers such as biphenyl and naphthalene, and from the quenchers in the triplet excited state back to chrysene in the ground state were observed to proceed at the diffusion-controlled rate. From dependence of the quenching efficiency on the quencher concentration, the lifetime of chrysene in the higher triplet excited state was estimated to be 60 ps with considering the time-dependent quenching.
Electrostatic charge effect on the orientational distribution of molecules on the water surface by Tetsuya Yamamoto; Takaaki Manaka; Mitsumasa Iwamoto (370-376).
The electrostatic charge effect on the orientational distribution of rod-like polar molecules at the air–water interface is analyzed taking into account the induced charge on electrode suspended in the air. The first order orientational order parameter S 1 is found to change as the electrode approaches monolayers, and approximately expressed as S 1=S 1 0+A *(2S 2 0−3S 1 02+1)/3, where A * characterizes the effect of electrode and Si 0 (i=1,2) represents orientational order parameters in the absence of suspended electrode. The molecular area giving the maximum deviation of S 1 from S 1 0 decreases as the interaction between molecules and water surface increases, but it is independent of the position of electrode.
Medium effects on the lowest 1(n,π *) excitation of 1,2,3-triazine in water by Daiqian Xie; Xiaohua Ma; Jun Zeng (377-383).
Solvent effects on the lowest 1(n,π *) excitation of 1,2,3-triazine have been studied using a method previously developed for estimating solvent shifts of species that have strong specific interactions with the solvent. The liquid structures are obtained from Monte Carlo simulations on dilute aqueous solutions of 1,2,3-triazine. Three hydrogen bonds to the ground state are found to be consistent with observed solvent shifts, and hydrogen bonding to the excited state is shown to be strong with one linear hydrogen bond to each symmetric nitrogen atom. The calculations provide a molecular analysis of the solvent shifts of the triazines in dilute solutions.
Ultrafast dynamics of photoinduced ring-opening and the subsequent ring-closure reactions of spirooxazines in crystalline state by Mototsugu Suzuki; Tsuyoshi Asahi; Katsutoshi Takahashi; Hiroshi Masuhara (384-392).
We investigated photoisomerization dynamics of spironaphthooxazine (SNO) and its chloro-substituted derivative (Cl–SNO) in crystalline phase by femtosecond diffuse reflectance absorption spectroscopy. Although the photoinduced ring-opening reaction occurred in 3 ps and <1 ps for SNO and Cl–SNO, respectively, photoisomerization to trans-planar photomerocyanine did not take place. The generated non-planar open form of SNO lived for 2 ns, while that of Cl–SNO returned to the spiro form in 1 ps. The crystalline phase results are compared to the analogous experiments in amorphous solids with a view of restricted conformational changes of molecules embedded in a crystal lattice.
A CASPT2 study of the doublet potential energy surface for the CH(X 2 Π)+N 2(X 1 Σ g +) reaction by Toshiyuki Takayanagi (393-398).
The HCN 2→H+NCN(3 Σ g −) reaction, which is a key process in the CH(2 Π)+N 2 reaction mechanisms, has been studied using the ab initio electronic structure method at the CASPT2 level theory. First, we calculated two-dimensional potential energy surfaces as a function of two appropriate coordinates in order to understand overall mechanisms. Then, full-dimensional stationary point searches have been carried out using locally interpolated potential energy surfaces. Our calculations strongly support the recent proposal of Lin and co-workers that the CH(2 Π)+N 2 reaction does not yield spin-forbidden N(4 S)+HCN products but yield spin-allowed H(2 S)+NCN(3 Σ g −) products.
Conformational potential energy surface of BrOONO by Antonija Lesar; Saša Prebil; Max Mühlhäuser; Milan Hodošček (399-407).
Cis-perp and trans-perp conformations with respect to N–O and O–O bonds were found to be the only stable ones on the BrOONO potential energy surface using the CCSD(T)//B3LYP method with the 6-311G* basis set. The energy for the cis-perp form is 2.0 kcal mol −1 lower than for the trans-perp form while the saddle point connecting the two minima is 9.0 kcal mol −1 above the cis-perp level. A comparison of the relative energetics for stationary points on the BrOONO, ClOONO, and HOONO conformational potential energy surfaces is discussed.
In situ reversible electrochemical switching of the molecular first hyperpolarizability by Inge Asselberghs; Koen Clays; André Persoons; Andrew M. McDonagh; Michael D. Ward; Jon A. McCleverty (408-411).
In situ reversible electrochemical switching of the molecular second-order nonlinear optical (NLO) polarizability, or first hyperpolarizability, has been implemented in a specially designed cell. The redox-switchable NLO chromophore is based on the octamethylferrocene/octamethylferrocenium redox system as electron-donor (D) group, in conjunction with nitrothiophene as the electron-acceptor (A) group and ethenyl as the π-conjugation bridge. This D–π–A chromophore has been shown to exhibit reversible redox switching of its linear and nonlinear optical properties. The importance and potential of this electrochemical switching of the first hyperpolarizability is discussed in the context of current and future applications of second-order NLO effects.
Light-induced change of charge transfer band in one europium doped aluminosilicate glass by Baojuan Sun; Hongwei Song; Jiwei Wang; Hongshang Peng; Xiaobo Zhang; Shaozhe Lu; Jiahua Zhang; Haiping Xia (412-415).
Ultraviolet light-induced spectral change in one Eu3+ doped aluminosilicate glass was studied. It was observed that the excited charge-transfer band decreased after irradiation. The intensity at the irradiated site decreased linearly with the power density of the irradiation light. This means that the light-induced change is a one-photon process. Irradiations at different wavelengths indicate that the spectral change is frequency-selective. The dark decay of the spectral change was also studied. At least two time constants were obtained. One constant is ∼2.5 h, and the other is longer.
Large-scale GaN nanobelts and nanowires grown from milled Ga2O3 powders by JiKang Jian; X.L. Chen; M. He; W.J. Wang; X.N. Zhang; F. Shen (416-420).
Large-scale hexagonal GaN nanobelts and nanowires were synthesized by direct reaction of milled Ga2O3 powders with flowing ammonia at 1000 °C. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray were used to characterize the structures, morphologies and compositions of the samples. The results show that those GaN nanobelts and nanowires are single crystals with hexagonal structure. The simple method presented here demonstrates that GaN nanobelts and nanowires can be grown on a large scale without using templates or catalysts.
A new ab initio potential energy surface describing acetylene/vinylidene isomerization by Shengli Zou; Joel M Bowman (421-424).
A new potential energy surface for C2H2 that describes acetylene/vinylidene isomerization is reported. The surface is an accurate, least-squares fit to nearly 10,000 symmetry-equivalent, ab initio electronic calculations obtained at the CCSD(T) level of theory, with an aug-cc-pVTZ basis. The ab initio geometries and normal-mode frequencies of the acetylene and vinylidene minima, and saddle point are reproduced very well by the fitted potential energy surface. Full-dimensional calculations of low-lying acetylene vibrational energies are also reported and compared to experiment.
High purity trigonal selenium nanorods growth via laser ablation under controlled temperature by Zhi-Yuan Jiang; Zhao-Xiong Xie; Su-Yuan Xie; Xian-Hua Zhang; Rong-Bin Huang; Lan-Sun Zheng (425-429).
By utilizing laser ablation, high purity trigonal selenium nanorods with different size have been synthesized from selenium powders. The high purity of the nanorods is attributed to freestanding growth process without catalyst or template. Its morphologies depend on both substrate temperature and reaction time. By controlling the experimental conditions, selenium nanorods with lateral dimensions in different range can be synthesized ranging from 20 nm to several hundred nanometers in width, and up to 10 μm in lengths.
Mixed L 2 basis set: STOs plus B-Splines. Calculation of the differential photoionization cross-section of Li2 by Roberto Moccia; Raffaele Montuoro (430-438).
The convenience afforded by the use of L 2 functions in the calculation of the photoionization cross-section and of others properties depending upon the electronic continuum has prompted the examination of particular basis sets that, among those derived, could be able to mimic the continuum states in an extended region of space. Here results are reported for the differential photoionization cross-section of the Li2 molecule, where a mixed L 2 basis set comprising multi-center STOs plus single-center radial B-Splines times spherical harmonics was employed.
Novel emission degradation behavior of patterned carbon nanotubes by field emission by Do-Hyung Kim; Hee-Sun Yang; Hee-Dong Kang; Hyeong-Rag Lee (439-444).
Field emission behavior of photolithography-based patterned carbon nanotubes (PP-CNTs) was irreversibly degraded, showing a gradual turn-on voltage shift to the high voltage region as a result of field emission measurements. The PP-CNTs show a flat region in Fowler–Nordheim (F–N) plots, which can be attributed to residue-induced emission suppression. The observed degradation in field emission can be attributed to a subsequent degradation of carbon nanotubes emitters by a combination of the high electric-field-induced straightening out effect and the high current-induced burning of PP-CNTs. The local emission current and the stability of electron emission were observed in an attempt to investigate the residue effect of the PP-CNTs on the field emission behavior.
Absolute chlorine atom quantum yield measurements in the UV and VUV gas-phase laser photolysis of CCl4 by Alexander Hanf; Almuth Läuter; Hans-Robert Volpp (445-451).
Absolute quantum yields Φ Cl+Cl* for the formation of chlorine atoms were measured under collision-free conditions for the gas-phase dissociation of carbon tetrachloride (CCl4) after pulsed laser photoexcitation at 193 and 135 nm. By means of a photolytic calibration method, where the gas-phase photolysis of HCl was utilized as a reference, values of Φ Cl+Cl* (193 nm)=1.5±0.1 and Φ Cl+Cl* (135 nm)=1.9±0.1 could be obtained which demonstrate the importance of the ultraviolet (UV) and vacuum-UV photolysis of CCl4 as an efficient source of atomic chlorine formation.
Parallel tempering-cavity-bias algorithm in the Gibbs ensemble by Vanessa Ortiz; Johnny R. Maury-Evertsz; Gustavo E. López (452-457).
A new algorithm in the Gibbs ensemble is presented where statistical sampling is improved by combining the cavity-bias and parallel tempering formalisms. The parallel tempering allows the method to surmount large free energy barriers in the potential energy surface while the cavity-bias technique improves the probability of particle transfer. The method was used to construct Cailletet–Mathias curves for the liquid–vapor equilibrium of a three-dimensional Lennard–Jones fluid. An accurate computation of the critical parameters for this system was obtained. Details about the implementation of the method and a comparison with previous studies are presented.
Spontaneous alignment of tetracene molecules in 4He droplets by Nikolas Pörtner; Andrey F. Vilesov; Martina Havenith (458-464).
The polarization dependence of the laser induced fluorescence and absorption was investigated for single tetracene molecules embedded in 4He droplets having N ̄ 4=3×103–3×105 atoms. The measurements revealed an increase in the intensity up to 20% in the spectra, when the laser polarization vector was aligned parallel to the direction of the droplet beam as compared to the perpendicular alignment. This observation suggests a spontaneous alignment of the molecules in the laboratory frame. A mechanism of the molecular alignment in the pick-up process is proposed.
A–X transition of SnO+: a theoretical study by Dipankar Giri; Kalyan Kumar Das (465-472).
Relativistic configuration interaction calculations have been carried out to obtain the electronic structure and spectroscopic properties of the low-lying electronic states of SnO+. Potential curves of several Λ–S states have been generated. Spectroscopic constants of the X 2 Π , A 2 Σ + , and B 2 Σ + states are estimated. The spin–orbit coupling is included in two steps. The computed dissociation energies of the ground and first excited states of SnO+ are compared with the experimental values. The vertical ionization potentials of the ground-state SnO to the ground and first excited states of SnO+ have been calculated. The electric dipole moment functions of the X 2 Π and A 2 Σ + states of SnO+ are also calculated. The effect of the spin–orbit interaction on the A 2 Σ +–X 2 Π transition is discussed in detail. The radiative lifetimes of the excited A 2 Σ + and B 2 Σ + states are reported.
A novel partition function for partially asymmetrical internal rotation by Gernot Katzer; Alexander F. Sax (473-479).
A novel partition function for one isolated internal rotation degree of freedom is presented. Our partition function is designed for torsion potentials with one antiperiplanar and two isoenergetic synclinal (gauche) minima, as in 1,2-dichloroethane or butane. Calculating thermodynamic functions (U,S,C v ) for the internal rotation in a number of small carbon and silicon compounds, we compare the results to those obtained with a symmetrical internal rotation partition function. The relative energy of the conformers affects the heat capacity most strongly, and gives an additive increment to the internal energy at high temperatures.
Acceleration of charge separation by oscillations of the environment polarization by D. Abramavicius; V. Gulbinas; L. Valkunas (480-485).
A new model explaining fast charge separation from optically achievable charge transfer (CT) states in molecular complexes is suggested. The idea is based on the assumption that the polarization reaction to the charges generated in the initial CT state can be divided into two evolution paths along fast and slow reaction coordinates. A possibility of the charge transfer rate enhancement by the oscillations of the system along the slow polarization coordinate is demonstrated.
Electronic, vibrational and magnetic properties of a novel C48N12 aza-fullerene by Rui-Hua Xie; Garnett W Bryant; Vedene H Smith (486-494).
The structural, electronic, vibrational and magnetic properties of a novel C48N12 aza-fullerene are studied by using density functional and Hartree–Fock methods. Optimized geometries and total energy of this aza-fullerene are calculated. The HOMO–LUMO gap of C48N12 is found to be about 1 eV smaller than that of C60. Fifty-eight IR-active frequencies and 10 NMR spectral signals are predicted for C48N12. Diamagnetic shielding factor, polarizability and hyperpolarizability of C48N12 are calculated. Our results suggest that C48N12 may have potential applications as semiconductor components and possible building materials for nanometer electronics, photonic devices and diamagnetic superconductors.
ODMR of the photoexcited triplet state of donor–acceptor complexes of naphthalene donor with pyromellitic dianhydride, 1,2,4,5-tetracyanobenzene, and 1,3,5-trinitrobenzene acceptors by Sanjib Ghosh; Christina Stuart; Andrzej Ozarowski; Ajay Misra; August Maki (495-501).
Odmr measurements of photoexcited triplet state traps were carried out at 1.2 K on polycrystalline donor–acceptor complexes of naphthalene (N) with the acceptors pyromellitic dianhydride (PMDA), 1,2,4,5-tetracyanobenzene (TCNB), and 1,3,5-trinitrobenzene (TNB). The zero field splittings (zfs) are consistent with a locally excited N triplet state with considerable admixture of charge transfer character that increases in the order N/TNB<N/TCNB≈N/PMDA based on zfs. The complexes reveal sublevel-selective enhancements of decay rate constants that are similar for N/TCNB and N/PMDA, but the pattern differs in N/TNB, suggesting a different donor–acceptor interaction for the latter.
Full quantum mechanical molecular dynamics using Gaussian wavepackets by Graham A. Worth; Irene Burghardt (502-508).
We present the first application of a promising new method for quantum dynamics calculations. Based on the efficient multiconfiguration time-dependent Hartree wavepacket propagation algorithm, it can treat part, or all, of the wavepacket using Gaussian functions. The Gaussian parameters evolve using variational, coupled equations of motion. In this way the Gaussian basis functions evolve so as to optimally describe the wavepacket. Here, a four-dimensional Henon–Heiles potential surface is used to demonstrate that only a few Gaussian functions are required, and convergence on the full quantum mechanical result is rapid.
Erratum to: ‘Silicon nanotubes: Why not?’ [Chem. Phys. Lett. 364 (2002) 251] by R.Q. Zhang; S.T. Lee; Chi-Kin Law; Wai-Kee Li; Boon K. Teo (509).
Erratum to: ‘Bulk production of multi-wall carbon nanotube bundles on sol–gel prepared catalyst’ [Chem. Phys. Lett. 366 (2002) 555–560] by Yuesheng Ning; Xiaobin Zhang; Youwen Wang; Yanlin Sun; Lihua Shen; Xiaofang Yang; G. Van Tendeloo (510).