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The first two steps of performance analysis and design of transport systems usually consist of identifying the best spatial discretization of the considered study area, namely zoning, and of the relevant Origin-Destination (OD) matrix. In this framework, zones are generally delimited by physical obstacles such as rivers, transport infrastructures, or buildings that can be well-identified in satellite remotely sensed data. Assuming the availability of pre-existing zones and OD matrices for the considered study area, this paper defines a semiautomatic procedure that employs fusion with satellite imagery for supporting the zone discretization and the OD matrix refinement. The proposed approach is tested on a real-world case study consisting of the Italian city of Genoa.

The study of transition metal coordination complexes has played a key role in establishing quantum chemistry concepts such as that of ligand field theory. Furthermore, the study of the dynamics of their excited states is of primary importance in determining the de-excitation path of electrons to tailor the electronic properties required for important technological applications. This work focuses on femtosecond transient absorption spectroscopy of Cobalt tris(acetylacetonate) (Co(AcAc)3) in solution. The fast transient absorption spectroscopy has been employed to study the excited state dynamics after optical excitation. Density functional theory coupled with the polarizable continuum model has been used to characterize the geometries and the electronic states of the solvated ion. The excited states have been calculated using the time dependent density functional theory formalism. The time resolved dynamics of the ligand to metal charge transfer excitation revealed a biphasic behavior with an ultrafast rise time of 0.07 ± 0.04 ps and a decay time of 1.5 ± 0.3 ps, while the ligand field excitations dynamics is characterized by a rise time of 0.07 ± 0.04 ps and a decay time of 1.8 ± 0.3 ps. Time dependent density functional theory calculations of the spin-orbit coupling suggest that the ultrafast rise time can be related to the intersystem crossing from the originally photoexcited state. The picosecond decay is faster than that of similar cobalt coordination complexes and is mainly assigned to internal conversion within the triplet state manifold. The lack of detectable long living states (>5 ps) suggests that non-radiative decay plays an important role in the dynamics of these molecules.

The chirality transfer control from a single molecule to the surface molecular superstructures and to the substrate is a challenging and important aspect of two-dimensional chiral nanostructures for tailoring the functionality of molecular--metal interfaces. However, how the chiral transfer takes place still remains an open question. In this paper, we combine data from scanning tunneling microscopy, low-energy electron diffraction and circular dichroism in the angular distribution of valence photoelectrons measurements to interpret the formation of extended chiral self-assembled domains obtained by adsorption of the chiral amino-alcohol alaninol on Cu(100). We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage, whereas a rotation of 14A degrees with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. This suggests that the reorientation originates from forces acting when tetramers pack together in the self-assembling process. Direct information on the chirality transfer from molecules to the substrate has been obtained by the dichroic behavior of a mixed molecule-copper valence state showing that the presence of molecular chiral domains induces asymmetric interaction with the substrate and locally transfers chiral character to the underlying metal atoms participating in the adsorption process.

The formation of 2D chiral monolayers obtained by self-assembly of chiral molecules on surfaces has been widely reported in the literature. Control of chirality transfer from a single molecule to surface superstructures is a challenging and important aspect for tailoring the properties of 2D nanostructures. However, despite the wealth of investigations performed in recent years, how chiral transfer takes place on a large scale still remains an open question. In this paper we report a coupling of scanning tunneling microscopy and low energy electron diffraction measurements with an original theoretical approach, combining molecular dynamics and essential dynamics with density functional theory, to investigate self-assembled chiral structures formed when alaninol adsorbs on Cu(100). The peculiarity of this system is related to the formation of tetrameric molecular structures which constitute the building blocks of the self-assembled chiral monolayer. Such characteristics make alaninol/Cu(100) a good candidate to reveal chiral expression changes. We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage or when geometrical confinement prevents long-range order. Conversely, a rotation of 14° with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. An insight to the process leading to a 2D globally chiral surface has been obtained by monitoring molecular assemblies as they grow from the early stages of adsorption, suggesting that the distinctive orientation of the self-assembled monolayer originates from a balance of cooperating forces which start acting only when tetramers pack together to form small clusters.

A photoelectron circular dichroism (CD) study of the valence states of 2-amino-1-propanol (alaninol) in the gas phase is presented. The aim of the investigation is to reveal conformer population effects in the valence-state photoelectron spectrum. The experimental dispersion of the dichroic D parameter of valence states as a function of the photon excitation energy is compared with its theoretical value calculated by employing a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian. The theoretical values are in very good agreement with the experimental data when the conformer population distribution is taken into account. Moreover, thanks to a comparison between experiment and theory, a clear assignment of the molecular orbital character and conformer geometry is given to the features of the photoelectron spectrum. This work indicates in a detailed experimental analysis that CD in photoelectron spectroscopy is an effective technique to disentangle the conformer assignment in photoelectron spectra.

The adsorption of a single molecule of the D-enantiomer of alaninol (2-amino-1-propanol) on the surface of Cu(100) is investigated through density functional theory calculations. Different possible adsorption sites for D-alaninol are tested, and it is found that the most stable configuration presents both amino and hydroxyl group covalently interacting with "on top" copper atoms. The electronic structure is analyzed in detail and compared with experimental photoelectron spectra. Another adsorption structure in which a dehydrogenation process is assumed to occur on the amino group is analyzed and provides a possible explanation of the valence band electronic structure and of the experimentally observed N 1s core-level shift at full coverage, where a self-assembled ordered chiral monolayer is formed on the copper surface.

We report the orthoaxial and axial X-ray circular dichroism spectra of a homochiral single crystal of {Λ-[Co(en)3]Cl3}2 · NaCl · 6H2O along with the linear dichroism of the same compound. The signs and magnitudes of the spectra confirm that the optical activity arises entirely from the interference between an electric quadrupole and electric dipole transition (E1E2 mechanism). By combining the results of the CD and LD spectra we have extracted the absolute values of the electric quadrupole and electric dipole contributions to the intensity of the 1s → 3d transition and compare these to an ab initio calculation.

Carboxylic terminated monolayers have been covalently attached on phosphorous doped crystalline (1 0 0) silicon surfaces using a cathodic electro grafting technique. The functionalization concentration and efficiency have been evaluated with different techniques. In particular, topographic images, performed with an atomic force microscope, were used to optimize the protocol in order to obtain a surface whose characteristics of uniformity and reproducibility are ideal for a bio-electronic device. Phase lag images of the functionalized surfaces were also performed, and show non-topographic structures that have been interpreted as areas of different molecule self-orientation. Poly-thymine oligonucleotides have been anchored on such a surface to form a nano-biosensing device capable to react selectively with a specific target molecule, a poly-adenine oligonucleotide. AFM images of high density (∼3 × 10 12 mol/cm 2 ) single strand and double strand covered samples show toroidal shaped structures formed by the self-assembly of the oligonucleotides on the silicon surface.

Two enantiomeric pairs of menthol derivatives, the menthol ester with 10-undecynoic acid and the 2-tricyanovinyl-pyrrole derivative of the methoxy-menthol, have been synthesized and their pure enantiomers obtained. The X-ray crystal and molecular structure of the (+)-enantiomer of the latter compound is reported.

In this study we modified and optimized a technique using an ordinary spin-coater device to deposit lipids on chemically etched silicon substrates. Tapping-mode atomic force microscopy is used for sample characterization, thereby realizing non destructive characterization with nanometrical resolution.

Lipids are the principal components of biologically relevant structures as cellular membranes. They have been the subject of many studies due to their biological relevance and their potential applications. Different techniques, such as Langmuir–Blodgett and vesicle-fusion deposition, are available to deposit ordered lipid films on etched surfaces. Recently, a new technique of lipid film deposition has been proposed in which stacks of a small and well-controlled number of bilayers are prepared on a suitable substrate using a spin-coater.We studied the morphological properties of multi-layers made of cationic and neutral lipids (DOTAP and DOPC) and mixtures of them using dynamic mode atomic force microscopy (AFM). After adapting and optimizing, the spin-coating technique to deposit lipids on a chemically etched Silicon (1,0,0) substrate, a morphological nanometer-scale characterization of the aforementioned samples has been provided. The AFM study showed that an initial layer of ordered vesicles is formed and, afterward, depending on details of the spin-coating preparation protocol and to the dimension of the silicon substrate, vesicle fusion and structural rearrangements of the lipid layers may occur.The present data disclose the possibility to control the lipid's structures by acting on spin-coating parameters with promising perspectives for novel applications of lipid films.

FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, from physics to chemistry to biology. Intense R&D programs have started in the USA and Europe in order to understand the SASE physics and to prove the feasibility of these sources. The allocation of considerable resources in the Italian National Research Plan (PNR) brought about the formation of a CNR–ENEA–INFN–University of Roma “Tor Vergata” study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated, leading to the SPARX proposal. We report in this paper the results of a preliminary start to end simulation concerning one option we are considering based on an S-band normal conducting linac with high-brightness photoinjector integrated in an RF compressor.

(1999). The elettra circular polarization beamline and electromagnetic elliptical wiggler insertion device. Synchrotron Radiation News: Vol. 12, No. 4, pp. 34-38.

The structural properties of strained InGaAs grown by molecular beam epitaxy on GaAs(100) substrates, have been studied by glancing‐angle extended x‐ray absorption fine structure (EXAFS). The very low incidence angle of the x‐ray beam on the sample makes it possible to collect the signal coming from a thin quasi‐surface layer allowing the study of a single strained sample built up by only 6 ML of InGaAs. The EXAFS results show that a slight deformation of the first shell Ga–As distance occurs and that the strain is accommodated also by bond‐bending mechanism as deduced by the second and third coordination shells analysis. The lattice expands in the growth direction in agreement within the limits predicted by the elastic theory.

Rotational strengths of the core electron excitations of the chiral molecule propylene oxide are calculated using the random phase approximation (RPA). As expected, the predicted values are small but still in the realm of experimental detectability, having dissymmetry factors g of the order of 10 −3 . The quality of RPA calculations for core excitations using the 6-31Gpol basis set is assessed via the comparison of calculated excitation energies and oscillator strengths with experimental and theoretical results for reference molecules.

Infrared and vibrational circular dichroism intensities have been evaluated theoretically for trans-(1S,2S)-dideuteriooxirane, trans-(1S,2S)-dideuteriocyclopropane, (S)-propylene oxide, and trans-(1R,2R)-dimethylcyclopropane molecules, via electric and electromagnetic nuclear shielding tensors determined by random-phase approximation within the framework of 6-31 g, 6-31 g ** , 6-31 gext, an d6-31 gpol Gaussian basis sets

Infrared and vibrational circular dichroism intensities have been evaluated theoretically for trans-(1S,2S)-dideuteriooxirane, trans-(1S,2S)-dideuteriocyclopropane, (S)-propylene oxide, and trans-(1R,2R)-dimethylcyclopropane molecules, via electric and electromagnetic nuclear shielding tensors determined by random-phase approximation within the framework of 6-31 g, 6-31 g ** , 6-31 gext, an d6-31 gpol Gaussian basis sets

We report the results of chemisorption in saturating conditions of D-alaninol on Cu(100) in term of the analysis of low-energy electron diffraction and scanning tunneling microscopy data. A large two-dimensional, single domain, ordered chiral structure of quadrangular tetrameric molecular units is formed. The four molecules interact differently with the surface in the two orthogonal directions.

Circular dichroism in the angular distribution of valence photoelectrons emitted from randomly oriented 3-hydroxytetrahydrofuran enantiomers (Th-S and Th-R) has been observed in gas-phase experiments using circularly polarized vacuum ultraviolet (VUV) light. The measured dichroism for both Th-S and Th-R, acquired at the single magic angle theta=234.73 degrees and at photon energies of 22, 19, 16, and 14 eV, points to an asymmetric forward-backward scattering of the photoelectrons from their highest occupied molecular orbitals (HOMO) HOMO-1 and HOMO-2, of up to 5%, depending on the photon energy. The asymmetry reverses on exchange of either the helicity of the radiation or the configuration of Th. The photoionization dichroic D parameters of Th-S and Th-R have been measured and their values discussed in the light of LCAO B-spline density functional theory (DFT) predictions. While an acceptable agreement is found between the dichroic parameter measured and calculated at the highest photon energy for the HOMO and HOMO-2 orbitals of Th, a significant discrepancy is observed for the HOMO-1 state which is attributed to the floppiness of Th, in particular to the comparatively large sensitivity of the size and shape of its HOMO-1 on nuclear vibrational motion.

We measured the total and partial ion yields of the two chiral amino acids alanine and serine in the gas phase both in the vacuum ultraviolet region and at the $\mathrm{C}(1s)$ edge using circularly polarized light. We did not detect any circular dichroism asymmetry larger than $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. A similar measurement of fixed-in-space amino acids yielded an upper limit of $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ for the stereoselective effect of circularly polarized light. The results obtained are relevant for quantitative models of stereoselective photodecomposition of amino acids that try to explain the homochirality of life.

Silicon and silicon nitride surfaces have been successfully terminated with carboxylic acid monolayers and investigated by atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). On clean Si surface, AFM showed topographical variations of 0.3-0.4 nm while for the clean Si3N4 surface the corrugation was around 3-4 nm. After material deposition, the corrugation increased in both samples with a value in topography of 1-2 nm for Si and 5-6 nm for Si3N4. The space distribution of specific chemical species was obtained by taking SNOM reflectivity at several infrared wavelengths corresponding to stretch absorption bands of the material. The SNOM images showed a constant contribution in the local reflectance, suggesting that the two surfaces were uniformly covered. (C) 2003 Elsevier B.V. All rights reserved.

We used DAFS to probe super-ordered domains in InGaP/GaAs epitaxial growth. The sample was lattice matched InGaP epitaxially grown on GaAs with a substrate miscut angle of 6 degrees with respect to the (001) direction. InGaP epi-layer exhibited (111)-type alloy ordering, of alternating InP and GaP - like planes and giving rise to a (-5/2,5/2,-5/2) Bragg peak reflection which becomes allowed. Structural data can be extracted, at the same time, for the surroundings of Gallium in the bulk and in the epi-layer from allowed reflections, while the forbidden reflection gives structural details around Gallium in the ordered domains. Difference with the bulk InGaP Fourier transform confirms the symmetry selectivity of chosen reflections for the super-ordered domains.

The Natural Circular Dichroism (NCD) of electronic and vibrational transitions has been widely used as a probe of molecular chirality. The extension of NCD to core transitions is now possible at third generation synchrotrons equipped with insertion devices which produce radiation with a high rate of circular polarisation. The first NCD measurements in the X-ray region were reported for core to valence state transitions of transition metal and lanthanide complex ions in oriented molecular crystals. Here we report the first NCD measurements on a randomly oriented system: the carbon K-edge absorption spectrum of a simple organic compound (methyloxirane) in the vapour phase. The signs and the intensity of the dichroism agree with previous calculations and indicate that a considerable hybridisation occurs between the core 1s and the valence molecular states. These results allow the possibility of direct assignment of the local chirality of single functional groups in a molecule. The observed dissymmetry factors are sufficiently large to support the hypothesis of differential photo-decomposition by circularly polarised X-ray as the origin of terrestial homochirality

An iron-containing product in the acetone extract from the lichen Cladonia deformis has been investigated using chemical, spectroscopic and X-ray crystallographic methods. Visible-near UV, EPR and IR spectra indicate that the iron is present as high-spin Fe(III) and coordinates in an oxygen-containing environment arising from graciliformin (or glaciliformin-like) ligands. This has been confirmed by an XAS (x-ray absorption) study using synchrotron radiation. Comparison of the EXAFS and XANES results with those obtained from model, tris(pent-2, 4-dionato) Fe(III), and detailed fitting using the single-scattering, curved-wave formalism for the EXAFS strongly supports the presence of a Fe(III) coordinated to five oxygen atoms from the graciliformin.

Carboxylic acid terminated (–COOH) monolayers (ML) have been covalently anchored on the surface (S) of crystalline silicon (Si) and silicon nitride (Si3N4) by using wet-chemistry methods. Their concentration has been determined adopting a stepwise procedure with a fluorescent probe in solution. First, 7-amino-4-methylcoumarin (H2N–C10H7O2, AMC) is covalently bonded to the monolayer on the surface through an amidation reaction forming an amide-terminated surface monolayer, S–(CH2)n–CO–NH–C10H7O2, then the surface is intensely washed in order to remove any physisorbed species, finally AMC is detached from the surface via hydrolysis of the –CO–NH– bond and quantified by a fluorescence analysis in water solution. The yields of both the amidation and hydrolysis reactions have been evaluated. By this method, submonolayers ≤0.1 ± 0.03 ML can be determined. It has been possible to evaluate the different extent of surface functionalization changing the substrate between Si and Si3N4 and for Si changing the monolayer formation reaction: heat- (Δ) or light- (hν) promoted or via cathodic electrografting (CEG). It came out that submonolayers are formed in any case, Si3N4 is functionalized to a larger extent than Si on heating (0.52 vs. 0.15 ML) and Si is best functionalized via cathodic electrografting: Δ, 0.15; hν 0.20; CEG, 0.44 ML. Surface topography of some monolayers on Si and Si3N4 substrates was investigated by Atomic Force Microscopy (AFM). On clean Si, AFM showed topographical variations of 0.3–0.4 nm while for the clean Si3N4 the corrugation was around 3–4 nm. After functionalization the two surfaces were uniformly covered and the corrugation increased in both samples with a corrugation in topography of 1–2 nm for Si and 5–6 nm for Si3N4.

The 1:1 PbO:V2O5 semiconducting glass prepared by quenching an equimolar mixture of PbO and V2O5 melt (650 °C) at liquid-nitrogen temperature has been investigated by XAS (X-ray absorption spectroscopy) at 25 and –180 °C. The spherical wave approximation was used, applying parameters extracted from the crystallographically known analogue PbV2O6(form I) at the same temperatures. At 25 °C the local geometry at Vv(i.e. V–O bonds

Two aspects of the Pfeiffer are distinguished. Each of these, enantiomer reequilibration and induced intermolecular optical activity, gives the differential free energy, enthalpy, and entropy of the enantiomers for intermolecular association in fluids. The salts, M3[Cr(ox)3], in chiral α-hydroxy ester solutions antiracemise to an enantiomeric excess with a magnitude, up to70%, dependent upon the particular cation, M+, and with a sign dependent upon the (R)- or (S)-configuration of the ester solvent. The effect is quenched by the addition of one equivalent per cation of a crown ether. The temperature-variation of the induced intermolecular CD of racemic [Cr(pd)3] in ethanol solutions of Δ-(−)K[As(cat)3] gives a differential enthalpy of 10.7 kJ mol−1 for the association of the chiral anion with the two [Cr(pd)3] enantiomers. The enantiomer in excess is found to form the larger and more stable association with the chiral environmental molecules. The stereochemical and energetic aspects of the homochiral and the heterochiral intermolecular associations are discussed.

The d–d dipole strengths of trigonal five-co-ordinated copper(II) complexes in microcrystalline form have been determined, together with the corresponding rotational strengths of the tris(2-aminoethyl)amine (tren) complexes [Cu(tren)(NCS)][SCN], and, as a single crystal, [Cu(tren)(NH3)][ClO4]2. The results are compared with the corresponding theoretical transition probabilities based upon the dynamic ligand-polarization mechanism. A consideration of the polarizability anisotropy of the chelate-ring bonds is required to account for the optical activity, and an overall negative d–d circular dichroism is found to characterize the δ conformation of the chelate rings in five-co-ordinate (tren) complexes of copper(II).

Nuclear electric and electromagnetic shieldings have been calculated for ethylene oxide and cyclopropane. These are respectively related to the atomic polar tensors (APT) and atomic axial tensors (AAT) used by IR and VCD spectroscopists. The rototranslational sum rules fulfilled by the nuclear shieldings are used to assess the quality of the theoretical values. Our results for the electromagnetic shieldings are compared with previously reported calculations.

The optimal catalyst for the oxidation of butane to maleic anhydride is believed to by γ-(VO) 2 P 2 O 7 1 formed by thermal treatment of VOHPO 4 0.5H 2 O at ca. 400°C 2 . The mechanism is topotactic, the change from face -shared to edge shared VOO 5 octahedra requiring no breaking of V-O-P bonds 2 . The last-mentioned is prepared from V 2 O 5 and excess H 3 PO 4 in EtOH 2 . A further product is obtainable from this reaction, (VOHPO 4 ) 2 2.5H 2 O EtOH, also a layered material but with an enlarged interlayer distance of 13.48 A 3 This “ethanol-pillared” material gives a calcination behaviour different than that of VOHP 4 0.5H 2 O. The XAS spectra of the freshly calcined products obtained along the TG curve (at 110, 230, 400, and 700° C) have been measured and analysed to cast further light on the topotacticity of precursors to V-O-P catalysts. Calcination at 700° C (Pt crucible) gave two distinct phases, one yellow and the other green; they were separated mechanically.

EXAFS studies of the calcium environments in polysaccharides have provided important insights into chain conformation and gel formation. Work on Ca2+ poly(α-D-galacturonate) in solid and gel forms ana on solid Ca2+ oligo(α-L-guluronate) is reviewed, with particular emphasis on the need to choose appropriate models mimicking well defined Ca-O bond distributions. The difference in environment for the solids provides the first structural evidence that Ca2+-polysaccharide interactions are sufficiently stereospecific as to participate in the control of gelation and other biologically important processes.

Optically pure Δ(–)[Cr(pd)3] and partly resolved [Ru(pd)3] with the Δ(+)isomer in excess are afforded by an asymmetric synthesis from the corresponding (+)-tartrate complex (pd = pentane-2,4-dionate). Complexes rac-[M(pd)3](M = CoIII, CrIII, RhIII, or RuIII) partition between diethyl (+)-tartrate and (–)-α-pinene with a partial resolution of the optical isomers, the Λ isomer being generally the more soluble in the ester layer. The optical isomers of [Rh(pd)3] have been obtained from the racemic complex through the optically enriched fractions provided by the differential partitioning.

The ENDOR spectra of the metastable expanded layer solid VOPO4·5H2O and its congener VOPO4·2H2O [both containing very small amounts of vanadium (IV)] have been measured at 4 K. The latter gave no ENDOR, whereas the former provided a spectrum in which three different proton signals ascribable to two interlayer water molecules were detected. From a reconstruction of the interlayer, taking into account the layer expansion of 3.1 A due to the intercalated water molecules, it is suggested that VOPO4·5H2O is an example of a ‘pillared’ material.

The EXAFS spectra of Co2+- and Ni2+-exchanged zirconium phosphates (mainly the α-forms) have been measured using synchrotron radiation. The M—O bond distances obtained are correlated with geometries inferred from electronic spectra. It is confirmed that there are changes in site geometry with degree of loading and calcination temperature. There is also further support for the presence of distorted tetrahedral sites in the anhydrous layered α-forms.For all the materials, a second shell is visible between 2.4 and 2.87 A(non-phase-shift corrected) depending on the particular material; these are ascribed to M⋯P distances.The gross changes in these second-shell distances, the M—O bond distances and the inter-layer distances are combined to suggest sites for the metal ions. As for the Cu2+ analogues, the zirconium phosphate layers do not remain rigid after exchange and calcination, but slide (and, perhaps, twist) to accommodate the CO2+ or Ni2+.

The extended X-ray absorption fine structure spectra of powered [Cu(NH3)5][BF4]2 have been measured at room temperature and at 77 K using synchrotron radiation. Standard Fourier-transform and least-squares fitting methods {utilising [Cu(en)2][BF4]2(en = ethylenediamine) as a model complex for extracting amplitude and phase parameters for Cu–N bonds} demonstrate that in each case only a single shell is present about the metal ion, i.e. all five Cu–N bonds are of equal length.

Interaction of the low-spin species bis(2-methylimidazole)tetratolylmesoporphyrinatoiron(III)[(TTP)Fe(2-MeIm)2] with Cu(acac)2(Hacac = acetylacetone) in chloroform leads to the high-spin species (TTP)Fe–2-MeIm–Cu(acac)2; spectral evidence indicates that magnetic interaction· between the CuII and the FeIII is weak.