FT‐Raman and FT‐IR spectral and quantum chemical studies on some flavonoid derivatives: Baicalein and Naringenin

In this study, the experimental and theoretical results on the molecular structures of some flavonoid derivatives (Baicalein and Naringenin) are presented. The FT‐IR and FT‐Raman spectra of the compounds have been recorded together for the first time between 4000–400 cm⁻¹ and 3500–5 cm⁻¹ regions, respectively. The molecular geometry and vibrational wavenumbers of the compounds have been also calculated in their ground states by using ab initio HF and DFT/B3LYP functional with 6‐31G(d,p) basis set used in calculations. The calculations were utilized to the C₁ symmetries of the molecules. All calculations were performed with Gaussian 98 software. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Scale factors have been used in order to compare how the calculated and experimental data are in agreement. Theoretical infrared intensities were also reported. Copyright © 2008 John Wiley & Sons, Ltd.     

Spatial and electronic structures of the germanium-tantalum clusters TaGe n − (n = 8–17)

The results of optimizing the spatial structure and calculated electronic spectra of the TaGe _n ^? anion clusters (n = 8–17) have been presented. The calculations have been performed in terms of the density functional theory. The most probable spatial structures of clusters detected in the experiment have been determined by comparing the calculated and available experimental data.     

Investigation of the neutron emission spectra of some deformed nuclei for (n,xn) reactions up to 26 MeV energy

In this study, neutron-emission spectra produced by (n,xn) reactions up to 26 MeV for some deformed target nuclei as ¹⁶⁵Ho, ¹⁸¹Ta, ¹⁸⁴W, ²³²Th and ²³⁸U have been investigated. Also, the mean free path parameter’s effect for (n,xn) neutron-emission spectra has been examined. In the calculations, pre-equilibrium neutron-emission spectra have been calculated by using new evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model. The reaction equilibrium component has been calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.     

FT‐Raman,FT‐IR spectral and DFT studies on 6, 8‐dichloroflavone and 6, 8‐dibromoflavone

In this study, experimental and theoretical vibrational spectral results of the molecular structures of 6,8‐dichloroflavone (6,8‐dcf) and 6,8‐dibromoflavone (6,8‐dbf) are presented. The FT‐IR and FT‐Raman spectra of the compounds have been recorded together between 4000 and 400 cm⁻¹ and 3500–5 cm⁻¹ regions, respectively. The molecular geometry and vibrational wavenumbers of 6,8‐dcf and 6,8‐dbf in their ground state have been calculated by using DFT/B3LYP functional, with 6‐31 + + G(d,p) basis set used in calculations. All calculations were performed with Gaussian03 software. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Scale factors have been used in order to compare how the calculated and experimental data are in agreement. Theoretical infrared intensities are also reported. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparative first-principles analysis of the absorption spectra of ZnAl2S4 and ZnGa2O4 crystals doped with Cr3+

Systematic first-principles analysis of the energy level schemes and ground state absorption spectra of trivalent chromium in ZnAl₂S₄ and ZnGa₂O₄ crystals has been performed in the present paper. The recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multi-electron (DV-ME) method [K. Ogasawara et al., Phys. Rev. B 64, 115413 (2001)] was used in the calculations. The method is based on the numerical solution of the Dirac equation; no phenomenological parameters are used in the calculations. As a result, complete energy level schemes of the Cr³⁺ ion and its absorption spectra in both crystals were calculated, assigned and compared with experimental data. By performing analysis of the molecular orbital (MO) population, it was shown that the covalency of the chemical bonds between the Cr³⁺ and S^2- ions is more significant than that one between the Cr³⁺ and O^2- ions.     

Two-phonon Raman spectra of LiH and LiD crystals

The experimental two-phonon Raman spectra of LiD and LiH are reported here. A deformation dipole model formulated elsewhere for LiD is used to compute the lattice dynamics of LiD and LiH required in the Raman intensity calculations. The use of the same model for LiH is justified by the good agreement between the peak positions of the temperature-weighted two-phonon density of states and the various experimental spectra. The Raman intensity calculations are carried out by treating the second-order expansion coefficients in the polarisability tensor as adjustable parameters. The need for the parameters associated with the next-nearest-neighbor ions is clearly demonstrated for all the spectra. A single set of six parameters for the T₂₈ spectra and thirteen parameters for the E₈ (or A₁₈) spectra is found to explain all the experimental spectra of LiD and LiH quite well. Since the polarisability of Li⁺ is very small, the need for the second-neighbor positive-positive parameters reflects on the extended and highly polarisable nature of the H^? or D^? ion.     

Ab Initio Calculations and Raman and SERS Spectral Analyses of Amphetamine Species

Abstract

For the first time, the differences between the spectra of amphetamine and amphetamine-H⁺ and between different conformers are thoroughly studied by ab initio model calculations, and Raman and surface-enhanced Raman spectroscopy (SERS) spectra are measured for different species of amphetamine. The spectra of amphetamine and amphetamine-H⁺ samples were obtained and assigned according to a comparison of the experimental spectra and the ab initio MO calculations, performed using the Gaussian 03W program (Gaussian, Inc., Pittsburgh, PA). The analyses were based on complete geometry minimization of the conformational energy of the S-plus-amphetamine molecule and the S-plus-amphetamine-H⁺ ion. The harmonic frequency calculations provide information about the characteristic features of the Raman spectra and the nature of the bonding in the molecule. It is concluded that vibrational bands from salt anions with internal bonds (sulfates, hydrogen phosphates, etc.) need to be taken into account when employing these spectra for identification purposes. These results also show how Raman spectroscopy can assist the forensic community in drug profiling studies. Furthermore, because their spectra are different, discrimination between the free and protonated forms of amphetamine salts can be observed. Here, we provide evidence for this difference and show experimentally how it has been overseen.     

g-boson excitations in the interacting boson model

We have extended the interacting boson model (IBM) by including the g-boson degree of freedom. Schematic model calculations have been carried out in the two different limits: SU(5) and O(6). Particular applications have been carried out for ¹⁰⁴Ru, a nucleus intermediate between SU(5) and O(6). In all cases, energy spectra, E2 and E4 transition rates have been studied in detail and compared with the most recent experimental data for ¹⁰⁴Ru.     

Nuclear level densities in <Superscript>208</Superscript>Bi and <Superscript>209</Superscript>Po from the neutron spectra in the (<Emphasis Type="Italic">p,n</Emphasis>) reactions on <Superscript>208</Superscript>Pb and <Superscript>209</Superscript>Bi nuclei

The spectra of neutrons from the (p, n) reactions on the ²⁰⁸Pb and ²⁰⁹Bi nuclei were measured in the proton-energy range 8–11 MeV. These measurements were performed by using a time-of-flight spectrometer of fast neutrons on the basis of the pulsed tandem accelerator EGP-15 of the Institute of Physics and Power Engineering (Obninsk, Russian Federation). A high resolution and stability of the time-of-flight spectrometermade it possible to identify reliably low-lying discrete levels alongwith the continuum section of the neutron spectra. The measured data were analyzed on the basis of the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations were performed by using the precise formalism of Hauser-Feshbach statistical theory together with the generalizedmodel of a superfluid nucleus and the back-shifted Fermi gas model for the nuclear-level density. The nuclear-level densities in ²⁰⁸Bi and ²⁰⁹Po were determined along with their energy dependences and model parameters. Our results are discussed together with available experimental data and recommendations of model systematics.     

Does the simple statistical model describe delayed neutron emission?: The cases of 85As, 87Br, 135Sb and 137I

Delayed neutron spectra and branching ratios to excited states in final nuclei calculated with the statistical model are compared to experimental data for the decay of ⁸⁷Br, ¹³⁷I, ⁸⁵As and ¹³⁵Sb. For the first two precursors, the calculations support the experimental β-strength functions reported previously. For the latter two, it is shown that the statistical model cannot simultaneously reproduce both spectra and branching ratios for any choice of β-strength function when all levels populated by neutron emission are included in the calculations. The comparisons demonstrate that partial widths for neutron emission are not compatible with optical-model transmission coefficients. We conclude, as pointed out previously, that structure effects in the energy range probed by delayed neutron emission are not averaged out to the extent required by the statistical assumptions.     

Structural, spectroscopic and crystal field analyses of Ni2+ and?Co2+ doped Zn2SiO4 powders

In this paper we presented structural and spectroscopic study of zinc silicate powder samples doped with divalent nickel and cobalt ions. Results of the Rietveld structural refinement, combined with optical spectroscopic study and theoretical crystal field calculations, are presented and discussed. X-ray diffraction studies were performed to establish reliable structure of the doped samples; in this way the interionic distances and chemical bond angles in Zn₂SiO₄:Co²⁺ and Zn₂SiO₄:Ni²⁺ were calculated and are reported for the first time. The room temperature reflection spectra of the prepared samples were measured in a spectral region from 4000 to 50000 cm^?1. The exchange charge model of crystal field has been applied to analyze the experimental spectra and assign all observed details in the spectra to the corresponding electronic transitions between the Co²⁺ and Ni²⁺ crystal field energy levels. The only input information for the model calculation was the experimentally obtained structural data, which were used for the calculations of the crystal field parameters with subsequent diagonalization of the crystal field Hamiltonian for both ions. Agreement between the calculated and experimentally detected energy levels of impurity ions was good. On the basis of the crystallographic and crystal field studies it was established that there exists a systematic trend of preferential occupation of one out of two possible crystallographic sites (namely, Zn2) for both impurity ions.     

X-ray emission spectra and electronic structure of VO,VN, VC

The experimental K_β5 and L_α emission spectra for vanadium and K_α spectra for nonmetal are studied for vanadium monoxide, nitride and carbide. Using the spectra unfolding the experimental molecular orbital diagrams have been obtained. By the semiempirical Mulliken-Wolfsberg-Helmholz method with the self-consistency on charges and configurations the calculations of electronic structure of clusters [VO₆]^10?, [VN₆]^15? and [VC₆]^20? have been carried out. The results of calculations are compared with the X-ray data. The effects of chemical bonding and charge densities on metal atoms in VO, VN, VC are discussed.     

Alpha particles from the reaction12C +12C at 28.7 MeV/nucleon

A classical dynamical alpha-cluster model has been developed and applied in order to get inclusive energy spectra of alpha particles produced in the collision of¹²C +¹²C at the beam energy 28.7 MeV/A. Results of the calculations are compared with experimental data. The shapes of the experimental energy spectra and the absolute normalization at forward angles are approximately described without any free parameters. The model makes it possible to distinguish alpha particles originating from the compound system and from direct processes. The spectra at forward angles are dominated by projectile fragmentation processes. The cross section at larger angles is overestimated, which is partially due to emission of particles other than alpha particles in central collisions. The evaporation Hauser-Feshbach model predicts that alpha particles emitted from the compound nucleus constitute less than 26% of all emitted particles.     

The Aniline—Water Complex

The rotational spectra of aniline–water and its¹⁸O isotopomer have been studied in the microwave region between 3 and 26.5 GHz using a pulsed molecular beam FT microwave spectrometer. The spectra were described in terms of a centrifugally distorted asymmetric rotor. Assuming a linear hydrogen N…H–O bond and that the water molecule was located in the symmetry plane of aniline, two structures turned out to be possible. In structure (I) the free water proton is directed toward the aniline ring. In structure (II) the proton is bent away from it.Ab initiocalculations indicate that only structure (I) is supported by the experimental results.     

Investigation of the electronic structure of the BiSBr and BiSeBr clusters by density functional method

The energy levels of valence bands (VB) of the BiSBr and BiSeBr crystals have been calculated for investigation of the photoelectron emission spectra of BiSBr, BiSeBr and BiSI crystals. The molecular model of this crystal has been used for the calculation of VB by the Density Functional Theory (DFT) method. The molecular cluster, consisting of 20 molecules of BiSBr, BiSeBr, has been used for calculations of averaged total density of states, including atom vibrations. The spectra of the averaged total density of states from VB of BiSBr and BiSeBr clusters have been compared with the experimental photoelectron emission spectra from VB of BiSI crystals. The results clarify that the atomic vibrations in A⁵B⁶C⁷ type crystals with chain structure create a smoother appearance of the averaged total density of state spectrum and the experimental X-ray photoemission spectra (XPS).     

Spectroscopic Studies of Oxygen-Bridged Copper (II) Cluster Somplexes; (II) Trinuclear Copper (II) Complex of Pyridine-2-Carbaldehyde Oxime

Abstract

Power electron paramagnetic resonance spectrum of the trinuclear complex Cu3L3 (OM)X2, xH20 (L=pyridine-2-carbaldehyde oxime, X=1/2 S04^2?, x=16.3) was recorded in the X-band region and interpreted in terms of a quarte (S=3/2) spin system.

Vibrational studies of the complex has also been undertaken and an assignment was made of the bands observed it the low frequency infrared and Raman spectra. It was shown that the central metallic core has a C3v syametry. Theoretical calculations of the frequencies of the vibrations related to this skeleton were performed and the results are it agreement with the experimental data.     

Surface structure of In2O3(111) (1 × 1) determined by density functional theory calculations and low energy electron diffraction

The surface structure of In₂O₃(111) has been investigated by dynamical analysis of low energy electron diffraction data, in conjunction with first principles calculations using density functional theory. The experimental data set consisted of eight independent beams whose intensities were measured for incident energies in the range between 25 eV and 250 eV. In fitting the experimental data it was essential to treat the radii of In and O spheres as variable parameters: following this procedure a final Pendry R factor of 0.31 was obtained. The LEED results are compatible with the calculations and both analyses suggest that the surface structure involves only small vertical relaxations in the outermost of the {[O^2?]₁₂^24?[In³⁺]₁₆⁴⁸⁺[O^2?]₁₂^24?} quadrupolar units that define the (111) surface. The ab initio slab calculations also confirm that lateral relaxations not considered in fitting the experimental data are of very minor importance.     

Influence of spin-orbit coupling on vibronic spectra of metalocomplexes porphin: Manifestation of out-of-plane vibrations

In fine-structure phosphorescence spectra of metallocomplexes of porphin with ions of the Pd(II) and Pt(II) and their meso-deuterated derivatives additional lines have been detected which have no analogs in fluorescence and resonance Raman spectra of metalloporphyrins and in phosphorescence spectra of metallocomplexes of porphin with light ions of the Mg(II) and Zn(II). For Zn-porphin, quantum-chemical calculations of frequencies and forms of in-plane and out-of-plane vibrations have been performed. Based on experimental data and calculation results it has been found, that in vibronic phosphorescence spectra of metallocomplexes of porphin, out-of-plane gerade modes of the E _g symmetry (D _4h symmetry group) are manifested. The activity of out-of-plane vibrations increases with enhancing spin-orbital coupling upon changing to heavier chelated metal ions. Vibronic transitions with participation of out-of-plane gerade E _g vibrations manifest in the T ₁ → S ₀ transition through the vibronic intensity borrowing from the triplet-triplet ³ E _u -³ E _g transition.