Chemical Physics Letters (v.396, #1-3)
Editorial board (IFC).
Catalyst-free growth of carbon nanotubes by laser-annealing of amorphous SiC films by S. Botti; L.S. Asilyan; R. Ciardi; F. Fabbri; S. Loreti; A. Santoni; S. Orlanducci (1-5).
The growth of carbon nanotubes usually requires a catalyst (typically Ni, Co or Fe). Although these catalysts promote the growth of nanotubes, they also require complex purifying treatments to remove them, which damage and dope the final product. Alternative catalyst-free growth of nanotubes films, as needed for electronic applications, was achieved by laser-annealing of amorphous SiC in vacuum at a relatively low temperature. In this work, we present the main results obtained and give some relevant examples of such carbon systems. The formation mechanism of carbon nanotube films is also discussed.
Synthesis of hybrid multiwall carbon nanotubes and their enhanced field emission properties by Ha Jin Kim; In Taek Han; Young Jun Park; Jong Min Kim; Jong Bong Park; Bum Kwon Kim; Nae Sung Lee (6-9).
We synthesized hybrid multiwall carbon nanotubes (CNTs) by consecutive growth with plasma enhanced chemical vapor deposition (PECVD) and thermal CVD. PECVD-grown CNTs contained the fragmented catalytic nanoparticles on their sidewalls. Subsequent thermal CVD resulted in the secondary growth of CNTs on these catalytic nanoparticles. The CNTs grown by PECVD and thermal CVD showed the turn-on electric fields of about 4.5 and 3.5 V/μm for electron emission, respectively, whereas the hybrid CNTs exhibited the low turn-on field of about 3 V/μm. Such an improvement of field emission characteristics seems to be attributed to strong field enhancement at the secondary grown CNTs.
An interesting property of the Perdew–Wang 91 density functional by J. Langlet; J. Bergès; P. Reinhardt (10-15).
The decomposition of the interaction energies is compared for fragment-based Density Functional Theory and Symmetry-Adapted Perturbation theory (SAPT). From a multitude of different functionals we obtain for hydrogen-bonded model systems a close numerical coincidence between the Pauli repulsion using the Perdew–Wang 91 functional and the correlated SAPT van der Waals terms (exchange repulsion and dispersion).
Direct ab initio molecular dynamics study of CH 3 + + Benzene by Yasuyuki Ishikawa; Hulusi Yilmaz; Takeshi Yanai; Takahito Nakajima; Kimihiko Hirao (16-20).
An ab initio direct molecular dynamics study of the reaction of CH 3 + with benzene has been performed and the mechanism of reaction examined. Ab initio energy and gradient evaluations were done at the QCISD/6-31+G** and MP2/6-31+G** levels. The primary products of reaction were several isomeric forms of arenium ion (σ complex). The reaction proceeds through a single channel, a direct barrierless insertion of a methyl cation into benzene to form a σ complex. The direct insertion mechanism supports a recent quantum chemical study but differs from that posited in earlier experimental and theoretical studies of the reaction, which have assumed formation of a stable π complex. The molecular dynamics simulation shows that product arenium ions are internally energetic enough for a hydrogen to shift about the benzenium ring to form several isomers.
Growth of aligned ZnO nanorod arrays by catalyst-free pulsed laser deposition methods by Ye Sun; Gareth M. Fuge; Michael N.R. Ashfold (21-26).
Arrays of well-aligned ZnO nanorods were synthesized on a Si substrate at 600 °C by 193 nm pulsed laser ablation of a ZnO target in low pressures of oxygen. Electron microscopy and X-ray diffraction revealed highly c-axis aligned, ultra-thin, needle-like nanorods with tip diameters <50 nm growing vertically from the substrate. Many of the rods appear to be capped by particles, which high-resolution transmission electron microscopy shows to be ZnO also. It is suggested that these derive from post-growth crystallisation of oxygen rich molten zinc droplets that cap the nanorods during growth – indicating a vapour–liquid–solid growth mechanism. The room temperature photoluminescence spectra of these samples show strong, narrow bandwidth UV emission ∼380 nm and only weak visible emission.
A theoretical investigation on fullerene-like phosphorus clusters by Ju-Guang Han; Jorge A. Morales (27-33).
Representative fullerene-like phosphorus P n clusters in the range of 14 ⩽ n ⩽ 60 are for the first time investigated with density functional theory (DFT) and Hartree–Fock (HF) methods. Total energies, structural properties, binding energies, and HOMO–LUMO gaps of several P n clusters are systematically calculated and discussed. Present results indicate that all the P n clusters found on local energy minima are unstable with respect to dissociation into P4 molecules, with their stability decreasing almost monotonically with the cluster size in the range of 14 ⩽ n ⩽ 40. In agreement with density functional tight-binding (DFTB) results, P n clusters tend to behave differently from their C n and Si n equivalents as evinced by their decreased stabilities, pentagon-fusion patterns, and more expanded structures.
Modification of microcantilevers using layer-by-layer nanoassembly film for glucose measurement by Xiaodong Yan; Hai-Feng Ji; Yuri Lvov (34-37).
Here, we report a new approach of glucose measurement by using a multilayer modified microcantilever. Glucose oxidase (GOx)/polyethyleneimine (PEI) multilayer modified microcantilever underwent bending when it was exposed to glucose solutions. The magnitudes of bending were proportional to the concentrations of glucose. This technique provides a new platform for enzyme functionalized cantilever biosensors.
Surface energetics of hydroxyapatite: a DFT study by Weihua Zhu; Ping Wu (38-42).
The surface energetics of hydroxyapatite was studied using density functional theory within the generalized gradient approximation. The effects of slab thickness, vacuum width between slabs and surface relaxation on surface energy have been tested. The results show that as long as the vacuum width is 12 Å or more, the influence of vacuum width on surface energy is small. Slabs with a thickness of 15.6 Å are enough to obtain meaningful results. Relaxation of the slab surfaces has an apparent effect on surface energy. Surface relaxation modifies the relative order of the morphological importance compared with unrelaxation.
A TDDFT study of the ruthenium(II) polyazaaromatic complex [Ru(dppz)(phen)2]2+ in solution by Simona Fantacci; Filippo De Angelis; Antonio Sgamellotti; Nazzareno Re (43-48).
DFT/TDDFT calculations were performed to investigate the structural, electronic and optical properties of the [Ru(dppz)(phen)2]2+ complex in solution. TDDFT calculations in water show two groups of metal-to-ligand charge transfer (MLCT) transitions at ≈450 and 415 nm whose superposition gives account of the broad absorption band experimentally characterized at 440 nm. Also, a group of almost coincident MLCT transitions partially mixed with dppz intraligand π–π∗ transitions centered at ≈380 nm is found to give rise to the narrow absorption band experimentally found at 380 nm. Our results provide insight into the hypochromic shifts experimentally characterized upon intercalation of the title complex into DNA.
Surface characterisation of template-synthesised multi-walled carbon nanotubes by M.-R. Babaa; E. McRae; S. Delpeux; J. Ghanbaja; F. Valsaque; F. Béguin (49-53).
Physisorption studies and transmission electron microscopy have been used to characterise multi-walled carbon nanotubes (MWNTs) made by a template-synthesis technique. Microscopic investigations revealed formation of ‘branched nanotubes’ with significant irregularities in diameters and with structural defects on the external surfaces of the tubes. Krypton adsorption isotherms at 77 K were recorded; comparison of these isotherms with those obtained under the same conditions on well defined MWNTs made by the catalytic chemical vapour deposition (CCVD) technique is discussed in the light of the sample morphologies. The effect of annealing on the crystallinity of the surface is reported.
Voltage color tunable OLED with (Sm,Eu)-β-diketonate complex blend by R. Reyes; M. Cremona; E.E.S. Teotonio; H.F. Brito; O.L. Malta (54-58).
Light emission from organic electroluminescent diodes (OLEDs) in which mixed samarium and europium β-diketonate complexes, [Sm0.7Eu0.3(TTA)3(TPPO)2], was used as the emitting layer is described. The electroluminescence spectra exhibit narrow peaks arising from 4f-intraconfigurational transitions of the Sm3+ and Eu3+ ions and a broad emission band attributed to the electrophosphorescence of the TTA ligand. The intensity ratio of the peaks determined by the bias voltage applied to the OLED, together with the ligand electrophosphorescence, allows to obtain a voltage-tunable color light source.
New basis sets for xenon and the interaction polarizability of two xenon atoms by George Maroulis; Anastasios Haskopoulos; Demetrios Xenides (59-65).
We have constructed a sequence of new basis sets for xenon. They range from [9s8p7d1f] to [9s8p7d5f3g] and have been especially designed for intermolecular interaction studies. We have tested their performance by calculating ab initio and DFT values of the interaction dipole polarizability of two xenon atoms. We show that a widely used density functional theory method yields qualitatively correct interaction polarizability curves. Near the estimated equilibrium of R e ≈ 8.5a 0 for Xe2 second-order Møller–Plesset perturbation theory predicts a monotonic decrease of the anisotropy as Δ α int ( R ) / e 2 a 0 2 E h - 1 ≈ 7.42 - 2.24 ( R - R e ) + 0.31 ( R - R e ) 2 , in agreement with the recent experimental estimate.
A note on the electric multipole moments of carbon dioxide by George Maroulis (66-68).
We have obtained accurate values for the electric quadrupole (Θ) and hexadecapole moment (Φ) of carbon dioxide. A very large (19s14p8d6f1g) basis set consisting of 456 uncontracted Gaussian-type functions is thought to provide near-Hartree–Fock values for both properties, Θ = - 3.79 ea 0 2 and Φ = - 1.41 ea 0 4 . At the CCSD(T) level of theory a [8s5p4d2f] basis set yields ( d Θ / d R ) e = 1.26 ea 0 and ( d 2 Θ / d R 2 ) e = 2.71 e , ( d Φ / d R ) e = 24.5 ea 0 3 and ( d 2 Φ / d R 2 ) e = 76.6 ea 0 2 at the equilibrium bond length of R e = 2.192 a0. Our final estimate for the hexadecapole moment is Φ e = - 2.50 ± 0.05 ea 0 4 .
Chemisorption of atomic and molecular oxygen on Au and Ag cluster anions: discrimination of different isomers by Y.D. Kim; G. Ganteför; Q. Sun; P. Jena (69-74).
Structures of coinage metal clusters reacted with atomic and molecular oxygen were studied using Ultraviolet Photoelectron Spectroscopy and Density Functional Theory calculations. We show that O2 partially dissociates on Ag 2 - , and this dissociative chemisorption is a kinetically hindered step. For Au 4 O 2 - , in addition to the previously observed molecularly adsorbed oxygen, we are now able to synthesize a second isomer using atomic oxygen reagents, in which oxygen adsorbs dissociatively. We demonstrate that different isomers can be distinguished by comparative studies of chemisorption of atomic and molecular species on metal clusters, which is otherwise difficult.
Reaction mechanism of hydrogenation of carbon dioxide to formic acid in the presence of scandium oxide: a density functional study by Der-Yan Hwang; Alexander M. Mebel (75-82).
Density functional calculations of potential energy surfaces in the CO2/H2/ScO(2Σ+) system have been performed to investigate the reaction mechanism of CO2 hydrogenation to formic acid in the presence of ScO. The results show that ScO can easily form a variety of complexes with CO2 and H2, complexes of CO2 with HScOH, and a highly exothermic cyc-OC(H)OScOH molecule. Although transformation of the latter to ScO + HCOOH is impeded by the high barrier for hydrogen transfer from ScOH to HCO2, it is expected to be fast in the gas phase because the transition state is only 2.3 kcal/mol higher in energy than the reactants CO2 + H2 + ScO.
The probe dependence of solvation dynamics and rotation in the ionic liquid 1-butyl-3-methyl-imidazolium hexafluorophosphate by N. Ito; S. Arzhantsev; M. Maroncelli (83-91).
Solvation and rotational dynamics were measured using several solvatochromic probes in 1-butyl-3-methylimidazolium hexafluorophosphate ( [ bmim + ] [ PF 6 - ] ) to determine the sensitivity of these dynamics to the choice of probe. In all solutes an unresolved ultrafast component (<5 ps) and highly non-exponential solvation dynamics were observed, consistent with results of prior studies in imidazolium ionic liquids. Solvation times varied by a factor of ∼2 among the probes studied. Rotational correlation functions were generally non-exponential, but in all cases rotation times track solvent viscosity in the same manner as in conventional solvents.
Electronegativity and charge-injection barrier at organic/metal interfaces by J.X. Tang; C.S. Lee; S.T. Lee; Y.B. Xu (92-96).
Despite a large scatter in experimental data, charge-injection barrier at organic/metal interfaces has been traditionally described as a function of metal work function. By studying the interface between Alq3 and various metals with photoelectron spectroscopy, we show that the charge-injection barrier can be better described as a linear function of the metal electronegativity. This is consistent with our theoretical analysis in terms of a simple model involving metal-induced gap states in organic layer. The interface parameter S is calculated to be 0.8, in good accordance with the experimental value of 0.81. The present work presents a method for predicting the injection barrier at organic/metal interfaces and should be useful for designing various organic-based electronic and optoelectronic devices.
Effect of geometry on the time law of Liesegang patterning by István Lagzi; András Volford; András Büki (97-101).
Evolution of Liesegang patterns in 2D radially symmetric gel media was studied experimentally in the AgNO3/K2Cr2O7/gelatine system. Different initial conditions were applied by varying the radius of the hole from which the penetration of the invading electrolyte took place. Our results show that the characteristics of the final pattern weakly depend on this parameter. In order to see whether this dependence is in accordance with one of the most popular theories of Liesegang patterning a numerical model based on Ostwald’s supersaturation model has been solved in 2D and 3D. Results of these simulations are in a good agreement with the experimental observations. The time law was reformulated in order to incorporate the above mentioned geometrical effect.
Spectroscopic studies on the excited-state properties of the light-induced antiviral drug hypocrellin A loaded in the mesoporous solid by Lei Z. Zhang; Guo-Qing Tang; Bo-Wen Gao; Gui-Lan Zhang (102-109).
Hypocrellin A (HA) is encapsulated in the mesoporous material MCM-41 for the first time, and its excited-state behaviors are elucidated by means of steady-state spectroscopies and excited-state lifetime measurements. No ground-state tautomer of HA in the mesoporous solid is deduced based on the spectra observed. Normal fluorescence energy level results from the (l, aπ) state with pπ conjugation; the excited-state intramolecular proton transfer (ESIPT) fluorescence is mostly due to the two-photon excitation (or absorption) of HA. The ESIPT emission intensity becomes truly remarkable with increasing excitation laser intensities. The time-resolved fluorescence measurements are also performed as the further evidence.
Ab initio study of the hydrolysis of carbonyl difluoride (CF2O): importance of an additional water molecule by Tadafumi Uchimaru; Seiji Tsuzuki; Masaaki Sugie; Kazuaki Tokuhashi; Akira Sekiya (110-116).
Ab initio investigations on the gas-phase reaction pathways for the hydrolytic decomposition of CF2O molecule have indicated that the energy barriers for the reaction channels of CF2O with a single H2O molecule are significantly reduced when an additional H2O molecule is brought into the reaction system. The additional H2O molecule serves as a proton relay acting simultaneously as a proton donor and acceptor in the transition states. These findings may imply that reaction channels in which multiple, at least two, H2O molecules participate will be important for the homogeneous gas-phase hydrolysis of CF2O.
Effects of protonation on the dipole polarizability of monocyclic azines: a theoretical study by Humberto Soscún; Yaneth Bermúdez; Olga Castellano; Javier Hernández (117-121).
The effects of the N-atom protonation on the static dipole polarizability of a series of representative monocyclic azines (pyridine, pyrimidine, pyridazine and pyrazine) have been investigated using ab initio and density functional theory DFT methods. It was found that the protonation induces significant negative variations in the dipole polarizability of monocyclic azines. These variations, which are the consequence of depletion in the electronic charge of the overall molecule are linearly correlated to the azines experimental pK a.
Realization of the new summing algorithm on an NMR ensemble quantum computer by Daxiu Wei; Xiaodong Yang; Jun Luo; Xianping Sun; Xizhi Zeng (122-125).
A summing algorithm is to evaluate and sum up a set of function samples. The paper [J. Phys. A. 35, L597(2001)] presented a new summing algorithm using ensemble computing which results in an exponential speedup. Here, we experimentally implemented the new algorithm on a four-qubit liquid state nuclear magnetic resonance ensemble system.
Electron emission from individual nitrogen-doped multi-walled carbon nanotubes by Maya Doytcheva; Monja Kaiser; Marcel A. Verheijen; Marisol Reyes-Reyes; Mauricio Terrones; Niels de Jonge (126-130).
This report describes the measurements on individual nitrogen-doped multi-walled carbon nanotubes mounted on tungsten support tips. Both the current–voltage characteristics and the energy spectrum of the emitted electron beam revealed field emission behavior similar to that shown for the best metallic emitters. The experimental results correspond with numerical calculations based on electron microscopy images of the nanotubes. The work function was derived and amounted to 5.0 eV. Finally, it is shown that the emission process is highly sensitive to small amounts of impurities deposited on the surface of the nanotube.
Electrical properties in disk-like phenylene derivative in crystalline state by Atsushi Sugita; Kyoko Suzuki; Shigeru Tasaka (131-135).
We investigated electrical properties of disk-like phenylene derivatives embedded with dipoles (N,N′,N″-tri-n-octyl-1,3,5-benzenetricarboxamide (TOB)). Our experimental results revealed that TOB exhibited ferroelectric and pyroelectric properties in a crystalline state. Remnant displacement and coercive field were 10.5 mC/m2 and 14 MV/m, respectively, at 293 K by displacement–field hysteresis loop. Dielectric anomaly, associated with ferroelectric–paraelectric phase transition, was observed at 370 K. The pyroelectric signal of about β = 3.1 μC/m2 K was recorded at temperatures below the phase transition point.
Laser field designing by evolutionary algorithm for coherent control of molecular dynamics by M. Sugawara; M. Yamanouchi; S. Yabushita (136-141).
A versatile method for theoretical designing of laser pulses for coherent control of molecular dynamics based on evolutionary algorithm is presented. Extended normal distribution crossover (ENDX) together with minimal generation gap (MGG) is employed for laser parameter optimization. The method is applied to the selective excitation problem of isotope molecules.
A modified definition of the zeroth-order Hamiltonian in multiconfigurational perturbation theory (CASPT2) by Giovanni Ghigo; Björn O. Roos; Per-Åke Malmqvist (142-149).
A new shifted zeroth-order Hamiltonian is presented, which will be used in second-order multiconfigurational perturbation theory (CASPT2). The new approximation corrects for the systematic error of the original formulation, which led to an relative overestimate of the correlation energy for open shell system, resulting in too small dissociation and excitation energies. Errors in the D e values for 49 diatomic molecules have been reduced with more than 50%. Calculations on excited states of the N2 and benzene molecules give a similar improvement.
Bending vibration of platinum monocarbonyl PtCO: observation of the millimeter- and submillimeter-wave spectra in the ν2 excited vibrational state by Emi Yamazaki; Toshiaki Okabayashi; Mitsutoshi Tanimoto (150-154).
The millimeter- and submillimeter-wave spectra of PtCO in the ground and ν2 excited vibrational states were observed by employing a source-modulated microwave spectrometer. The PtCO molecule was generated in a free space cell by the sputtering reaction from a platinum sheet lining the inner surface of a stainless steel cathode using a dc glow plasma of CO and Ar. From the molecular constants determined for the ν2 excited state, especially the l-type doubling constant, its harmonic wavenumber was determined to be ≈420 cm−1, which resolved the reported discrepancy between the previous matrix-infrared and theoretical estimates.
Time-domain analysis of electronic spectra in superfluid 4He by J. Eloranta; H.Ye. Seferyan; V.A. Apkarian (155-160).
Electronic absorption spectra of impurities in superfluid helium is developed in time domain, using time-dependent density functional theory to describe liquid 4He and time-dependent perturbation theory to describe the electronic degrees of freedom of the impurity. Angularly isotropic potentials are used to describe the molecule–helium interactions in the ground and excited electronic states. The calculations rationalize experimentally observed phonon side-bands in 4He droplets and in bulk helium, and allow assignments of spectral features to specific motions of the liquid.
Density functional study of onion-skin-like [As@Ni12As20]3− and [Sb@Pd12Sb20]3− cluster ions by Jijun Zhao; Rui-Hua Xie (161-166).
A comprehensive study of the structural and electronic properties of the interesting onion-skin-like [As@Ni12As20]3− cluster ion, characterized by Moses et al. [Science 300 (2003) 778], was carried out using a plane-wave based density functional theory. The calculated interatomic distances agree well with experiment. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for [As@Ni12As20]3− are fivefold-degenerate with hu and hg symmetries, respectively, and its HOMO–LUMO gap is determined to be 0.2 eV lower than that of C60. The static dipole polarizability of [As@Ni12As20]3− is two times larger than that of C60. The optical gap of [As@Ni12As20]3− is redshifted by 1.4 eV relative to that of C60. The possibility of synthesis of [Sb@Pd12Sb20]3− is proposed.
Efficient encapsulation of gaseous nitrogen inside carbon nanotubes with bamboo-like structure using aerosol thermolysis by M. Reyes-Reyes; N. Grobert; R. Kamalakaran; T. Seeger; D. Golberg; M. Rühle; Y. Bando; H. Terrones; M. Terrones (167-173).
High yields of dense, ‘clean’ and uniform arrays of well-aligned carbon nanotubes, with bamboo-like structure encapsulating gaseous nitrogen, were obtained by thermolyzing uniform aerosols of ferrocene/benzylamine solutions at 850 °C. Electron energy loss spectroscopy (EELS) studies reveal that up to 90% of these tubes contain molecular nitrogen in their cores. The materials were characterized by scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and EELS elemental mappings using an Omega Filter microscope. We envisage the material useful for storing large concentrations of relatively heavy gases such as nitrogen in confined volumes.
Ipsocentric and allocentric methods of mapping induced current density by A Soncini; P.W. Fowler (174-181).
Distributed-origin strategies for calculating magnetic response in terms of locally paramagnetic (DZ) or diamagnetic (PZ) induced currents are compared in pure and in modified forms that push the origin towards nearby nuclei (DZ2, PZ2). For visualisation of ring-currents, ipsocentric DZ has practical and conceptual advantages, with interpretation in terms of well-defined orbital contributions, whereas for nuclear shieldings allocentric PZ2 has greater accuracy. Maps are presented for diatropic, paratropic and localised systems: benzene, planarised cyclooctatetraene, borazine, clamped benzenes. All variants give indistinguishable π-maps, but differ in the σ plane, near heavy nuclei. Mixed ipsocentric-mapping/allocentric-property-calculation combines efficiency and insight into magnetic aromaticity.
Reactive and non-reactive vibrational quenching in O + OH collisions by A.J.C. Varandas (182-190).
We report a dynamics study of both reactive and non-reactive O + OH(v′,j′) collisions under local thermodynamic disequilibrium. Besides the total rate constant for temperatures over the range 110 ⩽ T/K ⩽ 450, vibrationally specific ones are reported for quantum numbers v′ ⩽ 9. Unknown thus far, such kinetic parameters may be of relevance in modelling the OH nightglow in the middle atmosphere.
Picosecond dynamics in water-soluble azobenzene-peptides by H. Satzger; C. Root; C. Renner; R. Behrendt; L. Moroder; J. Wachtveitl; W. Zinth (191-197).
Ultrafast absorption changes are recorded for water-soluble cyclic azobenzene peptides containing the photoswitch (4-aminomethyl)-phenyl-azobenzoic acid (AMPB) and a bioactive peptide motif. They can be separated into the fast reactions in the AMPB chromophore and the slower response of the peptide moiety. While the fastest reactions display similar time constants as observed for AMPB peptides dissolved in DMSO the slower reaction dynamics assigned to vibrational cooling and motions of the peptide moiety are faster in water by a factor of up to two. The changes in the reaction times are explained by solvent heat capacity and viscosity.
Optically switchable behaviour of a dioxolene adduct of a cobalt-macrocycle complex by Chiara Carbonera; Andrea Dei; Claudio Sangregorio; Jean-François Létard (198-201).
Reflectivity and magnetic measurements show that Co(CTH)(Phendiox)]PF6 · H2O (CTH = dl-5,7,7,12,14,14-9,10-hexamethyl-1,4,8,11-tetraazacyclotetradecane and Phendiox = semiquinonato or catecholato forms of 9,10-dioxophenantherene) undergoes valence tautomeric interconversion cobalt(III)–catecholato to cobalt(II)–semiquinonato upon light irradiation. This compound is the simplest cobalt-o-dioxolene complex undergoing this transition. The critical temperatures of the photoinduced transition and of the entropy driven transition seem to be related by the same empirical relationships observed for iron(II) spin crossover compounds.
Photoinduced proton transfer from the green fluorescent protein chromophore to a water molecule: analysis of the transfer coordinate by Oriol Vendrell; Ricard Gelabert; Miquel Moreno; José M. Lluch (202-207).
The proton transfer from the green fluorescent protein chromophore to a nearby water molecule is studied by means of CASSCF, CASPT2 and TDDFT calculations. A 1πσ* electronic state is found to intersect with the photoactive 1ππ* electronic state along the proton transfer coordinate. This state crossing constitutes a possible non-radiative deactivation pathway of the photoexcited neutral form of the chromophore. A discussion on the performance of the different levels of theory employed is also given, focusing in the ability to correctly describe the 1πσ* electronic state.
Formation of [C5H6(NH3)2]+ and [NH4(NH3) m ]+ (m = 1–3) from size-selected aniline–ammonia cluster cations in intense laser fields by Ryuji Itakura; Kaoru Yamanouchi; Tomokazu Yasuike; Kiyohiko Someda (208-212).
The fragmentation and intracluster chemical reaction processes of size-selected aniline–ammonia cluster cations [aniline(NH3) n ]+ (n = 1–4) induced by intense femtosecond and nanosecond laser fields were investigated by tandem-type mass spectrometry. A new solute–solvent reaction to form [C5H6(NH3)2]+ was identified when the size of the cluster was increased to n = 4. On the basis of a quantum chemical calculation of the n = 4 cluster ion, it was inferred that one of the structural isomers of [aniline(NH3)4]+ is responsible for the chemical reaction through which a new type of strong intermolecular C–N bond is formed between the C5H6 moiety and one of the attached NH3 molecules.
High-resolution Fourier-transform intra-cavity laser absorption study of H12C13CH and H13C13CH at around 12 600 cm−1: a case of strong anharmonic resonances by Shengfu Yang; Markus Metsälä; Tommi Lantta; Piritta Suero; Raul Martinez; Olavi Vaittinen; Lauri Halonen (213-218).
Fourier-transform intra-cavity laser absorption spectroscopy has been used to record high-resolution vibration–rotation overtone spectra of carbon-13 substituted acetylenes, H12C13CH and H13C13CH, in the third CH stretching overtone region between 12 500 and 12 730 cm−1. The observed spectra of both species contain only parallel bands for which rovibrational spectroscopic parameters have been determined. Several anharmonic resonances have been identified and rotationally analysed using traditional vibration–rotation theory. Altogether six bands, which include ν 1 + 3ν 3 and 4ν 3 for H12C13CH and ν 1 + 3ν 3 for H13C13CH, have been observed for both species. Four of the six bands in each molecule are reported for the first time.