Comparison of the relative intensities of penning electron spectrum and photoelectron spectrum. Unsaturaated hydrocarbons

The Ne* (³P₂) Penning electron spectra and the Ne I photoelectron spectra of ethylene, benzene, 1,3-butadiene, and styrene were compared. The π bands in the Penning spectra showed enhancement relative to the σ bands in comparison with the corresponding photoelectron spectra, suggesting that Penning electron spectroscopy has potential value for the assignment of photoelectron bands.     

Time‐dependent density functional theory studies of the electronic absorption spectra of metallophthalocyanines of group IVA

Time‐dependent density functional theory (TD‐DFT) calculations were carried out in a comparative study of the electronic absorption spectra of lead(II) phthalocyaninate (PbPc), tin(II) phthalocyaninate (SnPc), tin(IV) dichlorophalocyaninate (PcSnCl₂), germanium(II) phthalocyaninate (GePc), and germanium (IV) dichlorophalocyaninate (PcGeCl₂) with the B3LYP method and LANL2DZ basis set. Our calculated bands correspond well with the experimental results. The electronic natures of all the bands in the absorption spectra are assigned and analyzed comparatively according to the calculated electronic transition contributions. With the increase of the dielectric constant from CHCl₃ to DMSO, all the electronic absorption bands are somewhat red shift, consistent with the shift rules measured experimentally. The radius of the central metals has great influence to the absorption spectra, especially for the B bands. The influence of the radius of the central metals to the absorption spectra of PcSnCl₂ and PcGeCl₂ is smaller than to the spectra of the nonplanar MPcs (M = Pb, Sn, and Ge). Axial ligands also greatly changed the electronic absorption spectra due to the change of the orbital energy level and the molecular symmetry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

A study of the reactive intermediate IF and I atoms with photoelectron spectroscopy

Angle-resolved photoelectron (PE) spectra were recorded for IF and I. These were prepared as primary and secondary products of the F + CH2I2 reaction. PE spectra were recorded with different IF-to-I ratios to evaluate the relative intensities of IF and I photoelectron bands where their bands were overlapped. Improved values were obtained for the vertical and adiabatic ionization energies of the IF(+)(X(2)Pi(3/2)) <-- IF(X(1)sigma(+)) and IF(+)((2)Pi(1/2)) <-- IF(X(1)sigma(+)) ionizations and for the spectroscopic constants omega(e) and omega(e)ex(e) for the two IF ionic states X(2)Pi(3/2) and (2)Pi(1/2). Equilibrium bond lengths r(e) of these IF ionic states were derived from the experimental relative intensities of the vibrational components and calculated Franck-Condon factors. Threshold photoelectron (TPE) spectra were also recorded under the same reaction conditions. On comparing the TPE and PE spectra, the contributions from atomic iodine were much more intense in the TPE spectra. No difference was seen between the vibrational envelopes of the two observed IF bands, and no extra structure was seen associated with the TPE bands of IF as has been observed in TPE spectra of other diatomic halogens. The extra features that were observed in the TPE spectra can be assigned to contributions from autoionization of known I Rydberg states.     

Temperature dependence of solid uranyl-tris-acetate fluorescence spectra

Fluorescence spectra of Na [UO₂ acetate₃] measured at liquid nitrogen temperature are evaluated as the sum of vibronic transition bands, 8 base frequencies were found which build long progressions with the total-symmetric uranyl vibration. IR, FIR and Raman spectra were used to assign the vibrational bands.     

Electronic gas-phase spectra of larger polyacetylene cations

The origin bands of the A 2Pi-X 2Pi electronic transition for three new linear polyacetylene cation chains, HC12H+, HC14H+, and HC16H+, have been recorded in the gas phase at approximately 30 K, located at 924.7, 1034.6, and 1144.0 nm. The absorption spectra were observed using a two-color two-photon ion-photodissociation experiment that utilizes the cooling capabilities of a 22-pole ion trap. Such spectra allow a direct comparison between laboratory and astrophysical data; however, no matches were found between the experimentally determined origin bands and the known diffuse interstellar bands.     

Raman and photoacoustic infrared spectra of fluorene derivatives: Experiment and calculations

Raman and photoacoustic (PA) infrared spectra of fluorene and four derivatives (2,3-benzofluorene, 2-methylfluorene, 2-ethylfluorene and 1,8-dimethylfluorene) were recorded and analyzed in this investigation. Mid- and far-infrared PA spectra were examined from about 2000 to 100 cm⁻¹. The Raman spectra spanned the same wavenumber range. Observed bands in both PA and Raman spectra were compared with DFT (harmonic) and variational (anharmonic) calculations, and with published spectra. The DFT calculations provided single-molecule frequencies, whereas the variational method yielded results for both monomeric and dimeric species. Many previously unknown bands, including numerous features due to combination and overtone transitions, were identified and assigned in this work.     

Low frequency vibrational spectra of some amino acids

Far-IR absorption and reflection spectra, as well as laser Mandelshtam–Brillouin and Raman scattering spectra of -glycine, β-alanine, -histidine, -tryptophane single crystals in the 0.2–400 cm⁻¹ range were investigated. It was revealed that the far-IR and Raman spectra of the amino acids under study contain more bands than predicted by factor-group analysis, thus indicating a possible contribution of low-energy intramolecular vibrations and overtones, as well as an emergence of forbidden vibrations. Some of the low-frequency bands have never, to our knowledge, been detected previously.     

IR spectra and structure of 2-aryl-3-hydroxypyridines

The IR spectra of methyl, chloro, and phenyl derivatives of 3-hydroxypyridines in CCl₄ solutions and in the crystalline state were studied. A comparison of the frequencies, half widths, and integral intensities of the bands of the stretching vibrations of the hydroxyl groups in the spectra of solutions of the 3-hydroxypyridine derivatives in CCl₄ with the characteristic OH bands in the spectra of phenols demonstrates that 3-hydroxypyridines exist practically completely in the hydroxy form in dilute CCl₄ solutions. The shift in the OH bands in the spectra of 2-phenyl-3-hydroxypyridine derivatives indicates that the OH group forms a -hydrogen bond with the phenyl ring. The presence also of a band of a free OH group is evidence for the existence of s-cis and s-trans conformers relative to the C-O bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–190, February, 1972.     

The He(II) photoelectron spectra of the fluorosubstituted ethylenes and their analysis by the Green's function method

The 30.4 nm He(II) photoelectron spectra of the fluorosubstituted ethylenes have been recorded. The assignment of all main bands is obtained from many-body Green's function calculations. The results from the semi-empirical HAM/3 method lead to a nearly identical assignment. For the mono- and difluoroethylenes, an unambiguous interpretation of the spectra can be established from empirical considerations alone. The set of spectra has been reexamined with respect to the “perfluoro-effect” rules. Also discussed are the ionisation energies as a function of the geminal FCF bonding angle and the similarity of the spectra of the cis and trans isomers of 1,2-difluoroethylene. Additional weak bands were detected in the energy region 21–24 eV in all spectra and were attributed to “shake-up” transitions on the basis of 2ph-Tamm-Dancoff Green's function calculations. The orbital model of ionisation breaks down for the ionisation out of the F(2s) and C(2s) orbitals in general. The calculations reveal a charge transfer character of the excitations accompanying ionisation from the C(2s) orbitals.     

Polarized Raman spectra and intensities of aromatic amino acids phenylalanine,tyrosine and tryptophan

The prominent marker bands in the Raman spectra of the aromatic proteinogenic amino acids phenylalanine, tryptophan and tyrosine have been reinvestigated. Previous studies have been extended by measuring intensities against NaClO₄ as an external standard. Raman spectra were divided into isotropic (trace scattering of symmetric vibrations) and anisotropic (quadrupole scattering of antisymmetric or symmetric vibrations). These intensity and polarization properties of the marker bands were followed through pH changes from about 11–13 to 1–2.     

Anharmonicity and Spectra–Structure Correlations in MIR and NIR Spectra of Crystalline Menadione (Vitamin K3)

Mid-infrared (MIR) and near-infrared (NIR) spectra of crystalline menadione (vitamin K₃) were measured and analyzed with aid of quantum chemical calculations. The calculations were carried out using the harmonic approach for the periodic model of crystal lattice and the anharmonic DVPT2 calculations applied for the single molecule model. The theoretical spectra accurately reconstructed the experimental ones permitting for reliable assignment of the MIR and NIR bands. For the first time, a detailed analysis of the NIR spectrum of a molecular system based on a naphthoquinone moiety was performed to elucidate the relationship between the chemical structure of menadione and the origin of the overtones and combination bands. In addition, the importance of these bands during interpretation of the MIR spectrum was demonstrated. The overtones and combination bands contribute to 46.4% of the total intensity of menadione in the range of 3600–2600 cm⁻¹. Evidently, these bands play a key role in shaping of the C-H stretching region of MIR spectrum. We have shown also that the spectral regions without fundamentals may provide valuable structural information. For example, the theoretical calculations reliably reconstructed numerous overtones and combination bands in the 4000–3600 and 2800–1800 cm⁻¹ ranges. These results, provide a comprehensive origin of the fundamentals, overtones and combination bands in the NIR and MIR spectra of menadione, and the relationship of these spectral features with the molecular structure.     

Vibrational spectra and noncovalent interactions of carbohydrates molecules

The differences between the vibrational spectra of carbohydrates of the same chemical structure caused by the noncovalent intra- and intermolecular interactions have been systematized. In the general case, these differences show up as the following specific features of changes in the bond intensities: change in the intensity ratio of closely spaced bands (IR and Raman spectra); selective change (increase, decrease) in intensities of individual bands (IR and Raman spectra); change (increase, decrease) in intensities of practically all bands (IR and Raman spectra); appearance of strong bands in the region of low frequencies from 50 to 200 cm⁻¹ (Raman spectra); appearance of strong diffuse bands in the low-frequency range with a simultaneous great reduction in the other bands (practical disappearance of the majority of bands) (Raman Spectra). The causes of such a kind of changes in the band intensities in the vibrational spectra of carbohydrates are discussed.     

Synthesis and characterization of novel phthalocyanines bearing quaternizable coumarin

The synthesis of novel metal-free and zinc phthalocyanines with four 3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin dye groups on the periphery were prepared by cyclotetramerization of a novel 3-[(2-diethylamino)ethyl]-7-[(3,4-dicyanophenoxy)]-4-methylcoumarin. The novel chromogenic compounds were characterized by elemental analysis, ¹H NMR, ¹³C NMR, MALDI-TOF, IR and UV–Vis spectral data. The electronic spectra exhibit bands of coumarin identity along with characteristic Q and B bands of the phthalocyanine (Pc) core. The IR spectra of all the Pcs showed three characteristic intense bands, at 1704 cm⁻¹ for the lactone carbonyl and two bands at 1489–1604 cm⁻¹ for the conjugated olefinic system.     

Study of structure and spectral characteristics of the binuclear zinc complex with (<Emphasis Type="Italic">E</Emphasis>)-2-({2-[3-(pyridin-2-yl)-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazol-5-yl]phenylimino}methyl)phenol

A study of the structure and spectral properties of the compound (E)-2-({2-[3-(pyridin-2-yl)-1H-1,2,4-triazol-5-yl]phenylimino}methyl)phenol and its binuclear complex with zinc was carried out by the quantum-chemical calculations at a level of density functional theory. Within the framework of the time-dependent density functional theory were calculated electron spectra of both compounds, which gave good agreement with experiment, and was revealed the nature of the absorption bands in the visible and near UV region taking into account the solvent effect. Complete interpretation of the absorption bands in the infrared spectra of the complex and protonated ligand was given, and the frequency shift and changes in the intensities of IR bands of the ligand at the complex formation were analyzed.     

Theoretical study of the satellite bands in the valence shell XPS spectra of N2, CO,O2 and NO molecules

The energies for the ionized states of N₂, CO, O₂ and NO are obtained by using an ab initio full valence configuration interaction. (FVCI) method with a minimal basis set. The intensities of the corresponding valence shell MgKα X-ray photoelectron spectroscopy (MgKα-XPS) spectra are estimated with plane wave approximation and the satellite bands in the observed spectra are analyzed. The present FVCI results give a quite reasonable interpretation of the bands, both with regard to the positions and the relative intensities. New assignments are proposed for some bands Of O₂ and NO.     

A new assignment of IR vibrational modes in mullite

A new assignment of IR absorption bands of mullite is presented on the basis of empirical studies in the 1400–400 cm⁻¹ vibrational range of mullite-type compounds in the systems Al₂O₃–SiO₂, Al₂O₃–GeO₂, Ga₂O₃–GeO₂, and Al₂O₃–Me₂O, Ga₂O₃–Me₂O (Me=Na, K, Rb). The powder samples were prepared by heat treatment of sol–gel derived precursor powders and by reaction sintering of oxide powders. The FTIR powder spectra of Al–Si, Al–Ge, and Ga–Ge mullite compounds are characterized by three band groups, designated as (a), (b) and (c). Due to the lack of group (a) bands in the alkaline aluminate and gallate spectra, this high-energetic band group is assigned to Si---O and Ge---O stretching vibrations. Group (b) bands are essentially determined by Al---O and Ga---O stretching vibrations with Al and Ga on T sites in tetrahedral coordination and by T---O---T bending modes, while the low-energetic group (c) bands are due to Al---O and Ga---O stretching vibrations in octahedral structural units. Details of the vibrational modes are discussed on the basis of the deconvoluted spectra.     

Far-infrared spectra of some β-hydroquinone clathrates

Far-infrared spectra (400-30 cm^?1) of Nujol mulls of the β-hydroquinone clathrates containing the following guest molecules were investigated: formic acid, formic acid-d₂, methanol, methanol-d₄, acetonitrile, acetonitrile-d₃, sulphur dioxide and also both of methanol and sulphur dioxide. The observed infrared bands of the mulls in the region of 4000-30 cm^?1 were classified into those due to the host lattice and those due to the guest molecules. On the basis of the comparison of the spectra, some bands were assigned to the translational or the rotational vibrations of guest molecules. Appearance of those bands suggested that some guest molecules are considerably bound in the cavities of the host lattice. Effect of temperature change on the bands was also measured.     

Ir spectra of the simplest stable proton solvates in methanol and ethanol

The spectra of (MeOH)₂H⁺ and (EtOH)₂H⁺ proton disolvates formed by strong symmetrical hydrogen bonding were separated from the multiple frustrated total internal reflection (MFTIR) IR spectra of solutions of HCl in methanol and ethanol. These spectra show a large number of rather narrow bands, exceeding the number of bands in the spectra of the pure alcohols and are in accord with a model, in which the generation of continuous absorption in solutions of strong acids is a consequence of the interaction of vibrations for protons in a strong, symmetrical hydrogen bond with the vibrations of other groups of proton disolvates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 217–220, January, 1991.     

Raman Spectra of 1,2,4-Triazole-3-carboxylate Solution

Raman spectra of 1,2,4-triazole-3-carboxylate (TC^- anion) and its ring-deprotonated derivative (dpTC^2- dianion) in aqueous solutions were measured respectively. The density functional theory calculations were performed using MN15 functional and PCM solvent model to investigate their structures, as well as the vibrational frequencies and Raman intensities. With the aid of the calculated spectra, all the observed Raman bands of dpTC^2- were clearly assigned, with taking into account the deuteration shifts. Moreover, various protonic tautomers of TC^- anion were compared in the present theoretical calculations, and 2H-tautomer was found more stable. The experimental Raman spectrum of TC^- solution was roughly consistent with the calculated spectrum of the monomeric 2H-tautomer of TC^-, but some splits existed for a few bands when compared to the calculated spectra, which might be contributed by the hydrogen-bonding dimers of TC^-.     

Infrared spectra of the dihydrates of calcium selenate and yttrium phosphate - comparison with the spectrum of gypsum

The infrared spectra of protiated and deuterated CaSeO₄·2H₂O and YPO₄·2H₂O were compared with the spectrum of gypsum (CaSO₄·2H₂O) with which the two investigated compounds are almost certainly iso- structural. From the position of the bands in the OD stretching region of the spectra of partly deuterated compounds having low deuterium content, one may conclude that the strength of the hydrogen bonds which water molecules form with the anions increases in the order sulfate, selenate, phosphate. While studying the spectra of mixed crystals, particular attention was payed to the bands originating from the stretching vibrations of the tetrahedral anions.