Theoretical investigation of photoelectron spectra of furan,pyrrole, thiophene,and selenole

The ionization spectra of furan, pyrrole, thiophene, and selenophene have been calculated within the framework of the nonempirical quantum-chemical method with the Green's one-particle function in the approximation of the third order algebraic diagram construction [ADC(3)]. The calculated energies and the intensity of vertical transitions pertaining to the ionization of outer and inner shells are compared with the newest experimental data. The good agreement of theoretical and experimental results enabled a detailed assignment and interpretation of the observed photoelectron spectra to be carried out. Problems of disturbing the picture of orbital ionization are considered; the mechanism of formation of low-lying photoelectron satellites is explained. Certain general rules and trends of the behavior of the spectra of the systems studied are considered. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1366–1379. September, 2008.     

Molecular-orbital calculations on transition-metal complexes: Charge-transfer transitions and the interpretation of photoelectron spectra

The results of some molecular-orbital calculations on some transition-metal complexes according to a novel all-valence electron method are summarized. A comparison is made between the calculated and experimental charge-transfer spectra. In addition, attention is drawn to the remarkable sequence of the energy levels and the resulting consequences for the interpretation of photoelectron spectra.     

Dynamic effect on the structure of X-ray photoelectron spectra of lanthanide fluorides and oxides

Dynamic effect on the fine structure of X-ray photoelectron spectra of lanthanide oxides and fluorides is discussed. The Ln4p electron spectra are considerably complicated by the interaction between the configurations of themain one-hole and additional two-hole final states of 4p⁵4d⁵⁴fⁿ ↔ 4p⁶4d⁸fⁿ⁺¹ type. The effect of the nature of atoms in the nearest environment of lanthanide ions on the fine structure parameters is evaluated. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1059–1066, November–December, 1998.     

Theoretical study of many-body effects in the photoelectron spectra of unsaturated hydrocarbons

A theoretical investigation on the core and valence photoelectron spectra of unsaturated hydrocarbons of increasing complexity, ethylene, trans-butadiene, and trans-hexatriene, has been performed in order to analyze the role of the most important many-body effects on the spectral features and the evolution of these effects along the series. The capability of various configuration interaction (CI ) schemes to interpret both the core and the valence ionization satellite structures has been pointed out. The 3h-2v(π)-1p and 2h–1p CI schemes employed, together with an accurate choice of the basis set and the explicit inclusion of the relaxation, has proven to be very useful tools for this kind of study, being sufficiently accurate to explain the most important correlation features and extendible, at the same time, to longer chain systems. © 1994 John Wiley & Sons, Inc.     

Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids

We have recently measured core level and valence band XPS, UPS, and MIES spectra of two room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions ([Tf(2)N](-)) and either 1-ethyl-3-methyl-imidazolium ([EMIm](+)) or 1-octyl-3-methyl-imidazolium cations ([OMIm](+)). [T. Ikari, A. Keppler, M. Reinm?ller, W. J. D. Beenken, S. Krischok, M. Marschewski, W. Maus-Friedrichs, O. H?fft and F. Endres, e-J. Surf. Sci. Nanotechnol., 2010, 8, 241.] In the present work we analyze these spectra by means of partial density of states (pDOS) as calculated from a single ion pair of the respective ionic liquid using density functional theory (DFT). Subsequently we reconstruct the XPS and UPS spectra by considering photoemission cross sections and analyze the MIES spectra by pDOS, which provides us decisive hints to the ionic liquid surface structure.     

Theoretical study of shake-up in the core photoelectron spectra of the alkali atoms

Relativistic and non-relativistic Hartree-Fock calculations have been performed for the shake-up lines relative to core ionization of the alkali atoms. Good general agreement with the experimental data is achieved both for the energy and the intensity. Relativistic effects are found to be small, amounting TO = 0.2 eV in Cs. As concerns the shake-up energies, a correlation effect is detected, the magnitude of which increases along the series.     

Theoretical investigation of one- and two-photon spectra of pyrazabole chromophores

Abstract  

An extensive series of pyrazabole chromophores containing pseudo-conjugated systems have been theoretically constructed and investigated on the one-photon absorption (OPA) and two-photon absorption (TPA) properties by using density functional theory and Zerner’s intermediate neglect of differential overlap methods. The results indicated that all the pyrazabole chromophores show strong OPA at around 400 nm and intense TPA properties in the range of 500–600 nm with TPA cross sections (δ _max) as large as 540–3,560 GM, which are excellent candidates for optical power limiting materials. It is noteworthy that the δ _max values of the two constructed pyrazaboles, PA3 and PAF2, are 308.8 GM at 772.0 nm and 157.8 GM at 834.4 nm, respectively, which may be particularly attractive as probes for two-photon fluorescence imaging. The influence of incorporating electron acceptors in the central core, π-conjugated bridge and terminal groups on OPA and TPA properties was analyzed in detail to derive structure–property relationships and to lay the guidelines for both spectral tuning and amplification of molecular TPA in the target region. Meanwhile, the solvent effects on these properties were taken into account within the PCM model. The solvent has a significant impact on the TPA properties for chromophore PA3 and leads to the two-photon absorption spectra (λ _max ^T ) red-shift and δ _max enhancing relative to those in gas phase. In addition, from the calculations of molecule AlA2, we can draw the conclusion that the compounds with the Al₂N₄ center behave similarly to pyrazabole chromophores in the linear optical and TPA properties and increase TPA cross sections to some extent.     

Theoretical investigation of the structure and vibrational spectra of carbamoyl azide

Molecular structure and vibrational frequencies of carbamoyl azide NH2CO-NNN have been investigated with ab initio and density functional theory (DFT) methods. The molecular geometries for all the possible conformers of the molecule were optimized using DFT-B3LYP, DFT-BLYP and MP2 applying the standard 6-311++G** basis set. From the calculations, the molecule was predicted to exist predominantly in cis conformation with the cis-trans rotational barrier of about 7.91-9.10 kcal/mol depending on the level of theory applied. The vibrational frequencies and the corresponding vibrational assignments of carbamoyl azide in Cs symmetry were examined theoretically and the calculated Infrared and Raman spectra of the molecule in the cis conformation were plotted. Observed frequencies for normal modes were compare with those calculated from normal mode coordinate analysis carried out on the basis of ab initio and DFT force fields using the standard 6-311++G** basis set of the theoretical optimized geometry. Theoretical IR intensities and Raman activities are reported.     

阿魏酸分子结构和振动光谱的理论研究

阿魏酸是一种有效的天然油脂抗氧化剂.采用密度泛函理论(DFT) B3LYP方法和从头算HF两种方法,在6-311++G**基组水平上对阿魏酸分子的几何结构进行全优化,得到其几何结构参数,进一步计算得到阿魏酸的红外和拉曼振动光谱.计算结果表明,采用B3LYP和HF 2种方法优化得到的几何结构及频率值是一致的,对在B3LYP方法下计算得到的红外和拉曼振动频率进行合理的理论归属并与SDBS数据库实验数据进行比较,发现计算得到的红外和拉曼振动频率与实验测定结果符合较好.阿魏酸分子结构和振动光谱的研究,为研究阿魏酸及其衍生物的化学结构与生理活性之间的构效关系提供依据.     

Theory of lineshape in photoelectron and Auger spectra

A theory of lineshape in photoelectron spectra is developed based on the Green’s function calculation of the atomic vacancy structure. It is shown that the broadening of photoelectron lines is always somewhat asymmetrical, and the broadening of satellite lines arising in atomic photoionization is generally strongly asymmetrical and inverse. The approach is generalized to low-energy Auger spectra; it is shown that Auger decay lines of excited atomic states may narrow with respect to the width of the initial level. The results are compared with experimental photoelectron spectra. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 6, pp. 985–991, November–December, 1998.     

The conformation,UV-absorption spectra and photoelectron spectra of phenoxachalcogenins

The analysis of dipole moment data obtained for dibenzo-p-dioxin, phenoxathiin, phenoxaselenin and phenoxatellurin in benzene at 25°C in conjunction with EHT calculations of the ocnformational energies show that these molecules adopt a non-planar conformation in solution. Each of the phenoxachalcogenins is folded along the axis connecting the two heteroatoms. A butterfly flapping motion about the planar conformation canot be excluded. The uv and photoelectron spectroscopic data support the conclusions drawn from the dipole moment studies. The spectroscopic data were interpreted with the help of SCF-PPP-CI calculations.     

Topological effects displayed in absorption and photoelectron spectra

For topologically related pairs of isomers, S and T, a theorem we term TEMO (Topological Effects on Molecular Orbitals) has been derived; it organizes the MO pattern of the isomers so that in the range of two subsequent MO's of S there are alternately two and no MO's of T. It follows that depending on the number of electrons, the HOMO-LUMO separation in S and T differs in a topologically determined manner. The wave-lengths of the absorption maxima of the longest wave-length transitions in polycyclic aromatic hydrocarbons, polymethines, and heterocyclic compounds are in accord with TEMO. The photoelectron spectra of these compounds exhibit the TEMO pattern of their MO's even in cases where Koopmans' theorem fails.     

Paramagnetism and shake-up satellites in X-ray photoelectron spectra

The correlation between paramagnetism and the shake-up satellites in the X-ray photoelectron spectra of the 3d transitional-metal compounds is examined and explained in terms of modified selection rules governing the shake-up transitions.     

Calculated photoelectron spectra of singlet and triplet methylene

Vertical ionization potentials for singlet and triplet methylene are calculated by a CI perturbation method based on ab initio SCF molecular orbitals (6–31 G^** basis). The shape and vibrational fine structure of the first photoelectron band are investigated using the MINDO/3 method. The computed singlet-triplet splitting for methylene is 16.4 kcal/mol, in reasonable agreement with the experimental value of 19.5 kcal/mol.     

Ultraviolet photoelectron spectra of some resorcinols and dithioresorcinols

The photoelectron spectra of resorcinol, dithioresorcinol, 4,6-dichlororesorcinol 1, 4,6-dichlorodithioresorcinol 3 and their methyl derivatives were recorded by using He(I) and HE(II) excitations. The assignment of the photoelectron bands was mainly based on relative band intensity variations and on the results of ab initio STO-3G calculations. The results show clear evidence of the presence of intramolecular OH … Cl hydrogen bonding interactions in 1, while no effects of such a bonding was observed in the corresponding dithiocompound 3. These findings are confirmed by the STO-3G calculations. The photoelectron spectra of both 1,3-dithiomethoxybenzene and 1,3-dithiomethoxy-4,6-dichlorobenzene give evidence of rotational isomerism of the SCH₃ group.     

Vapor-phase core photoelectron spectra of para-nitroaniline and nitrosobenzene

Para-nitroaniline (PNA) and nitrosobenzene have been studied in the gas phase by X-ray photoelectron spectroscopy using Al Kα X-ray (1486.6 eV) radia     

The He-I photoelectron spectra of uranocene and thorocene

The bonding in unranocene and thorocene is discussed in the light of their photoelectron spectra and ionization of 5f electrons is identified.