共查询到20条相似文献,搜索用时 46 毫秒
1.
J. A. Wolny Y. Garcia I. Faus S. Rackwitz K. Schlage H. -C. Wille V. Schünemann 《Hyperfine Interactions》2016,237(1):65
The results of the nuclear inelastic scattering (NIS)/nuclear resonance vibrational spectroscopy (NRVS) for the powder spectra of dimeric [Fe 2L5(NCS) 4] (L = N-salicylidene-4-amino-1,2,4-triazole) complex are presented. This system is spin crossover (SCO) material tagged with a fluorophore that can sense or “feel” the SCO signal ripping through the molecular network and thereby providing an opportunity to register the SCO transition. The spectra have been measured for the low-spin and high-spin phases of the complex. The high-spin isomer reveals one broad band above 200 cm ?1, while the low-spin one displays two intense bands in the range from 390 to 430 cm ?1, accompanied by a number of weaker bands below this area and one at ca. 490 cm ?1. A normal coordinate analysis based on density functional calculations yields the assignment of the spin marker bands to particular molecular modes. In addition the vibrational contribution to the spin transition has been estimated 相似文献
2.
Hongxin Wang Yoshitaka Yoda Weibing Dong Songping D. Huang 《Journal of synchrotron radiation》2013,20(5):683-690
The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%‐57Fe‐enriched [Fe4S4Cl4]= and 10%‐57Fe and 90%‐54Fe labeled [Fe4S4Cl4]= has been well resolved; (ii) a quick‐switching energy calibration procedure, which reduces each calibration time from 3–4 h to about 30 min. Although the quick‐switching calibration is not in situ, it is suitable for normal NRVS measurements. 相似文献
3.
Nuclear inelastic scattering (NIS) of synchrotron radiation, also known as nuclear resonant vibrational spectroscopy (NRVS), has been shown to provide valuable insights into metal-centered vibrations at Mössbauer-active nuclei. We present a study of the iron-centered vibrational density of states (VDOS) during the first step of the Gif-type oxidation of cyclohexene with a novel trinuclear Fe3(μ3-O) complex as catalyst precursor. The experiments were carried out on shock-frozen solutions for different combinations of reactants: Fe3(μ3-O) in pyridine solution, Fe3(μ3-O) plus Zn/acetic acid in pyridine without and with addition of either oxygen or cyclohexene, and Fe3(μ3-O)/Zn/acetic acid/pyridine/cyclohexene (reaction mixture) for reaction times of 1 min, 5 min, and 30 min. The projected VDOS of the Fe atoms was calculated on the basis of pseudopotential density functional calculations. Two possible reaction intermediates were identified as [Fe(III)(C5H5N)2(O2CCH3)2]+ and Fe(II)(C5H5N)4(O2CCH3)2, yielding evidence that NIS (NRVS) allows to identify the presence of iron-centered intermediates also in complex reaction mixtures. 相似文献
4.
BAGLAYAN zge KESAN Gürkan PARLAK Cemal ALVER zgür SENYEL Mustafa 《中国科学:物理学 力学 天文学(英文版)》2014,57(9):1654-1661
FT-IR and Raman spectra of 1-cyclopentylpiperazine(1cppp)have been experimentally examined in the region of 4000–200cm-1.The optimized geometric parameters,conformational equilibria,normal mode frequencies and corresponding vibrational assignments of 1cppp(C9H18N2)are theoretically examined by means of B3LYP hybrid density functional theory(DFT)method together with 6-31++G(d,p)basis set.On the basis of potential energy distribution(PED)reliable vibrational assignments have been made and the thermodynamics functions,highest occupied and lowest unoccupied molecular orbitals(HOMO and LUMO)of 1cppp have been predicted.Calculations are employed for four different conformations in C1 and Cs point groups of 1cppp in gas phase.Comparison between the experimental and theoretical results indicates that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and the structural parameters,vibrational frequencies and assignments.Furthermore,C1(equatorial-axial)point group has been found as the most stable conformer of 1cppp. 相似文献
5.
N. Srinivasa Rao A.P. Pathak N. Sathish G. Devaraju V. Saikiran P.K. Kulriya D.C. Agarwal G. Sai Saravanan D.K. Avasthi 《Solid State Communications》2010,150(43-44):2122-2126
Ge nanocrystals embedded in an SiO2 matrix were prepared by the atom beam co-sputtering (ABS) method from a composite target of Ge and SiO2. The as-deposited films were rapid thermally annealed at the temperatures 700 and 800 °C in nitrogen ambience. The structure of the films was evaluated by using X-ray diffraction (XRD) and Raman spectroscopy. XRD results reveal that as-deposited films are amorphous in nature whereas annealed samples show crystalline nature. Raman scattering spectra showed a peak of Ge–Ge vibrational mode shifted downwards to 297 cm?1, presumably caused by quantum confinement of phonons in the Ge nanocrystals. Rutherford backscattering spectrometry has been used to measure the thickness and Ge composition of the composite films. Size variation of Ge nanocrystals with annealing temperature has been discussed. The advantages of ABS over other methods are highlighted. 相似文献
6.
用密度泛函理论B3LYP方法和6-311G(d,p)/Lanl2DZ优化得到黄曲霉素B1(AFB1)分子及其复合物AFB1-Ag的稳定结构,并计算了复合物的表面增强拉曼光谱和预共振拉曼光谱. 结果表明,AFB1分子的拉曼光谱很大程度依赖于吸附位点以及入射光的激发波长. 与分子的常规拉曼光谱相比,复合物表面增强拉曼光谱中C=O伸缩振动模的增强因子约为102~103复合物的极化率增强而导致的静态化学增强,并分析了振动模式的振动方向与其拉曼强度的关系.选择复合物最大吸收峰附近激发光266和482 nm以及远离共振吸收波长785和1064 nm作为入射光,计算得到不同入射光激发下复合物的预共振拉曼光谱.结果表明其增强因子最大达到104量级,主要是由电荷转移产生的共振增强引起的. 相似文献
7.
Mehmet Karabacak Mehmet Cinar Sahin Ermec Mustafa Kurt 《Journal of Raman spectroscopy : JRS》2010,41(1):98-105
In this work, the Fourier transform infrared and Raman spectra of 2‐bromonicotinic acid and 6‐bromonicotinic acid (abbreviated as 2‐BrNA and 6‐BrNA, C6H4BrNO2) have been recorded in the region 4000–400 and 3500–50 cm−1. The optimum molecular geometry, normal mode wavenumbers, infrared intensities and Raman scattering activities, corresponding vibrational assignments and intermolecular hydrogen bonds were investigated with the help of B3LYP density functional theory (DFT) method using 6‐311++G(d,p) basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. From the calculations, the molecules are predicted to exist predominantly as the C1 conformer. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
8.
Ljup?o Pejov Vladimir M. Petruševski 《Journal of Physics and Chemistry of Solids》2002,63(10):1873-1881
Fourier transform infrared spectra of isotopomeric 35ClO4− and 37ClO4− anions isomorphously isolated in potassium permanganate matrix were recorded at room and low temperature (LT, ∼100 K). On the basis of the detected second-order vibrational transitions involving the dopant species ν3 mode components, anharmonicity constants and harmonic eigenvalues for these modes were calculated. Although the overall appearance of the region of fundamental vibrational transitions in the spectra of dopant perchlorate anions may be better explained in terms of a pseudo-symmetry (the so-called ‘latent’ symmetry) site group C2v, corresponding to the pseudo-symmetry space group Imma, instead of the (rigorous) crystallographic Cs one (corresponding to the crystallographic Pnma space group), an opposite statement seems to be valid for the region of the second-order vibrational transitions. The vibrational mode mixing (a ‘Fermi-like’ resonance) of the ClO4− ν1 mode with the ν3a site group component is almost negligible. 相似文献
9.
The vibrational spectrum of a cadmium impurity atom in the HgTe crystal has been calculated using the microscopic theory of lattice dynamics in the approximation of a low impurity concentration. Within this theory, the behavior of the local and quasi-local modes induced upon substitution of the lighter Cd atom for the Hg atom in the region of the zero or very low one-phonon density of states in the HgTe crystal has been considered. It has been found that, apart from the local mode at a frequency of 155 cm?1, the calculated vibrational spectra exhibit a weak (but clearly pronounced) feature at a frequency of 134 cm?1, which coincides with the experimentally observed vibrational mode (the “minicluster” mode) at a frequency of 135 cm?1 in the Hg1 ? x Cd x Te (x = 0.2–0.3) alloys at 80 K. 相似文献
10.
Bogdan M. Leu Graeme R.A. Wyllie W.Robert Scheidt E.Ercan Alp J.Timothy Sage 《Journal of Physics and Chemistry of Solids》2005,66(12):2250-2256
High-resolution X-ray measurements near a nuclear resonance reveal the complete vibrational spectrum of the probe nucleus. Because of this, nuclear resonance vibrational spectroscopy (NRVS) is a uniquely quantitative probe of the vibrational dynamics of reactive iron sites in proteins and other complex molecules. Our measurements of vibrational fundamentals have revealed both frequencies and amplitudes of 57Fe vibrations in proteins and model compounds. Information on the direction of Fe motion has also been obtained from measurements on oriented single crystals, and provides an essential test of normal mode predictions. Here, we report the observation of weaker two-quantum vibrational excitations (overtones and combinations) for compounds that mimic the active site of heme proteins. The predicted intensities depend strongly on the direction of Fe motion. We compare the observed features with predictions based on the observed fundamentals, using information on the direction of Fe motion obtained either from DFT predictions or from single crystal measurements. Two-quantum excitations may become a useful tool to identify the directions of the Fe oscillations when single crystals are not available. 相似文献
11.
S. Ağduk G. Gökoğlu 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(4):509-514
We present the results of ab initio calculations of lattice dynamics and the second order
elastic stiffness constants of nickel-based magnetic shape memory alloy Ni2MnIn in
stoichiometric composition. The plane wave basis sets and pseudopotential
method within spin-polarized generalized gradient approximation (σ-GGA) scheme of the density functional theory (DFT) is applied. Elastic
constants are calculated by tetragonal and monoclinic isochoric strains
on cubic L21 structure. The calculated elastic constants
agree very well with the recent ultrasonic experimental data. Phonon dispersion spectra are investigated within linear response
technique
of the density functional perturbation theory (DFPT). A vibrational anomaly is observed in phonon spectra at the transverse
acoustic mode (TA2) in [ζ
ζ0]
direction at wavevector ζ = 0.3 as an indication of the structural instability of the system to shear deformation. This anomaly is also verified by
the
low shear modulus and large elastic anisotropy ratio. Phonon dispersion curves are in excellent agreement with the results
of recent neutron diffraction experiments. 相似文献
12.
We investigate the surface‐enhanced Raman scattering (SERS) spectra of flavin monoucleotide (FMN) in its different redox states and in a redox active enzyme, nitric oxide synthase. Incubated with silver nanoparticles coated with silica, spectra for oxidized and reduced FMN are obtained at different electrochemical potentials. Dominate Raman mode shifts at 1623/1610, 1567/1550, and 1502/1492 cm−1, belonging to typical redox‐sensitive region of FMN, are observed and analyzed, and they show a consistence with the results of spectral calculation by using the density function theory (DFT) method. We assign mode at 1500 cm−1, composed of N5―H bending, N1C10a stretching and the asymmetric C4a―N5―C5a stretching, as a spectroscopic indicator for the redox states of FMN, because it shows a significant downshift (1502/1492 cm−1) and non‐linearly correction with potentials when FMN gets reduced from its full oxidized state electrochemically. Isolated FMN domain from a wild type neuronal nitric oxide synthase enzyme (nNOS) is also studied with the same experimental approach. We have observed similar Raman mode down‐shifting as that of the pure FMN, which further supports our conclusion that the mode at ~1500 cm−1 indicates redox states for FMN, the coenzyme of nNOS, even in redox protein matrix. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
13.
14.
《Journal of Molecular Spectroscopy》1987,123(1):93-125
Propadienone is an interconverting molecule having a pair of equivalent symmetry related conformers separated by an energy barrier rising well above the vibrational ground state. Microwave spectra of molecules in excited states of the large-amplitude in-plane bending mode ν12, including intersystem lines, have been successfully represented using the semirigid bender model. The model reveals a double-minimum bending potential with a barrier rising 359 cm−1 above the minima at C1C2C3 = 142°. In the ground state the interconversion frequency is 3.7 GHz and the ν12 fundamental frequency is predicted to be 160 cm−1. Analysis of other vibrational satellites involving the lowest-frequency out-of-plane mode ν8 indicates a vibrational frequency of 240 cm−1. The inplane vibrational satellite and also the ground state substitution spectra are quite accurately reproduced by the model. Our generalized semirigid bender method offers a variety of approaches to fitting molecular parameters to the experimental data. 相似文献
15.
Szu‐Hsueh Lai Jung‐Wei Ling Yu‐Min Huang Min‐Jie Huang Chien Hung Cheng I‐Chia Chen 《Journal of Raman spectroscopy : JRS》2011,42(3):332-338
The Raman and infrared spectra of fac ‐tris(2‐phenylpyridinato‐N,C2′)iridium(III), Ir(ppy)3 and surface‐enhanced resonance Raman spectra of bis(2‐phenyl pyridinato‐) (2,2′bipyridine) iridium (III), [Ir(ppy)2 (bpy)]+ cation were recorded in the wavenumber range 150–1700 cm−1, and complete vibrational analyses of Ir(ppy)3 and [Ir(ppy)2 (bpy)]+ were performed. Most of the vibrational wavenumbers were calculated with density‐functional theory agree with experimental data. On the basis of the results of calculation and comparison of the spectra of both complexes and their analogue [Ru(bpy)3]2+, we assign the vibrational wavenumbers for metal–ligand modes; metal–ligand stretching wavenumbers are 277/307 and 261/236 cm−1 for Ir(ppy)3, and 311/324, 257/270, 199/245 cm−1 for [Ir(ppy)2 bpy]+. Surface‐enhanced Raman scattering spectra of [Ir(ppy)2 bpy]2+ were measured at two wavelengths on the red and blue edges of the low‐energy metal‐to‐ligand charge‐transfer band. According to the enhanced Raman intensities for the vibrational modes of both ligands ppy and bpy, the unresolved charge‐transfer band is deduced to consist of charge‐transfer transitions from the triplet metal to both ligands ppy and bpy. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
S. Lecoultre A. Rydlo C. Félix W. Harbich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,52(1-3):187-190
We report for the first time the absorption and fluorescence spectra of gold dimers in a neon matrix. The dimer absorption spectra show the A?←?X transition predicted from measurements in the gas phase and not observed so far in a matrix, as well as the so-called B?←?X and C?←?X transitions. Fluorescence measurements on the atom reveal new emission lines at 1.97, 3.59 and 4.09 eV that can be assigned to the 2P1/2?→?2D3/2, 2P1/2?→?2D5/2 and the 2P3/2?→?2D5/2 transitions. For the dimer, excitation of both A and B state results in distinct emission spectra with vibrational structure. 相似文献
17.
In this work, the experimental and theoretical vibrational spectra of N1‐methyl‐2‐chloroaniline (C7H8NCl) were studied. FT‐IR and FT‐Raman spectra of the title molecule in the liquid phase were recorded in the region 4000–400 cm?1 and 3500–50 cm?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (B3LYP) with the 6‐311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT‐IR and FT‐Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. 13C and 1H NMR chemical shifts results were compared with the experimental values. The optimized geometric parameters (bond lengths and bond angles) were given and are in agreement with the corresponding experimental values of aniline and p‐methyl aniline. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
J.U. Andersen E. Bonderup 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):435-448
Semi-empirical atom-atom potential energy calculations based on pairwise additive interactions are performed and, after applying
the Born-Oppenheimer approximation to separate high frequency vibrational modes from low frequency orientational and translational
modes, the infrared vibrational spectra of CO2 and N2O monomers trapped in an argon matrix at a temperature of 5 K are determined. It is shown that only a double substitutional
site in argon can accommodate N2O, whereas CO2 is trapped in two distinct sites, of single and double substitutional types. The model shows that splitting of the degenerate
mode occurs for both molecules in the double site. In the ground electronic state, the vibrational frequency shifts due to
the matrix and the vibrational transition moments for low-lying levels are determined using the contact transformation method,
as used for gas phase calculations. Calculated energy levels compare well with observed ones and the theory also predicts
some unobserved levels. Moreover, calculations show no significant changes in the dipole moments of both CO2 and N2O trapped molecules.
Received 22 March 2000 and Received in final form 10 May 2000 相似文献
19.
In this work, the experimental and theoretical UV, NMR and vibrational spectra of 2-chloro-6-methylaniline (2-Cl-6-MA, C7H8NCl) were studied. The ultraviolet absorption spectra of compound that dissolved in ethanol were examined in the range of 200–400 nm. The 1H, 13C and DEPT NMR spectra of the compound were recorded. FT-IR and FT-Raman spectra of 2-Cl-6-MA in the liquid phase were recorded in the region 4000–400 cm?1 and 3500–50 cm?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using density functional theory (DFT) employing B3LYP exchange correlation and the 6-311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies were found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital (GIAO) method. Comparison of the calculated NMR chemical shifts and absorption wavelengths with the experimental values revealed that DFT method produces good results. 相似文献
20.
提出一个新的二维变分方法计算PH3+(X2A2")的对称伸缩振动(v1)和伞形振动(v2). 因为采用了对称化的笛卡尔坐标,所以动能项变得简单,同时伞形振动模式也能得到很好的反映. 相比采用经常使用的一维模型计算伞形振动,这个二维模型不需要约化质量的假设,同时也考虑了v1和v2振动模式之间的相互作用. 用二维模型对PH3+首次进行了计算, 前七个能级的理论值和实验值的平均相对误差小于3 cm-1. 用相同的方法也计算了NH3,结果没有PH3+理想,说明这个方法有一定的局限性. 相似文献