Valence electronic structure of uranyl nitrate UO2(NO3)2·2H2O

Experimental and theoretical studies on the electronic structure of a uranyl nitrate hydrate, UO₂(NO₃)₂·2H₂O, have been performed by X-ray photoelectron spectroscopy (XPS) and with relativistic DV-Xα molecular orbital methods. The XPS spectra are measured within five minutes of X-ray irradiation, which causes negligible damage to the sample. Taking into consideration the calculated results, each peak of the experimental spectrum is assigned. The theoretical spectrum of the uranyl nitrate is in good agreement with the present experimental spectrum.     

The electronic delocalization in para‐substituted β‐nitrostyrenes probed by resonance Raman spectroscopy and quantum‐chemical calculations

The electronic (UV‐vis) and resonance Raman (RR) spectra of a series of para‐substituted trans‐β‐nitrostyrenes were investigated to determine the influence of the electron donating properties of the substituent (X = H, NO₂, COOH, Cl, OCH₃, OH, N(CH₃)₂, and O⁻) on the extent of the charge transfer to the electron‐withdrawing NO₂ group directly linked to the ethylenic (C = C) unit. The Raman spectra and quantum chemical calculations show clearly the correlation of the electron donating power of the X group with the wavenumbers of the ν_s(NO₂) and ν (C = C)_sty normal modes. In conditions of resonance with the lowest excited electronic state, one observes for X = OH and N(CH₃)₂ that the symmetric stretching of the NO₂, ν_s(NO₂), is the most substantially enhanced mode, whereas for X = O⁻, the chromophore is extended over the whole molecule, with substantial enhancement of several carbon backbone modes. Copyright © 2008 John Wiley & Sons, Ltd.     

Ultraviolet photoelectron spectra of gas phase and condensed tin and lead dihalides (MX2 ; M = Sn,Pb; X = Cl,Br, I)

The photoelectron spectra and electronic structures of the methylene dihalides, CH₂X₂ (X = F, Cl, Br and I), have been calculated by the overtapping-spheres SCF-Xα-MS method. The results are in good agreement with experimental data. Calculated assignments of the spectra are also presented and interpreted by assuming interaction between lone-pair and bonding orbitals.     

The photoelectron spectra of the oxalyl halides (COX)2, [X = F,Cl and Br]

We have examined the HeI photoelectron spectra of the oxalyl halides (COX)₂, (X = F, Cl, and Br). We assume the presence of the trans-isomer onWe have used semi-empirical calculations (SCF MO), and Koopmans' Theorem, as aids in assigning the spectral bands.     

Photoelectron spectra of fluorotribromomethane and fluorotrichloromethane

High resolution He(I) photoelectron spectra are reported for fluorotribromomethane CFBr₃ and fluorotrichloromethane CFCl₃. The assignments are based on CNDO/2 calculations, symmetry arguments, the fine structures of the bands, and comparison with the photoelectron spectra of related compounds. Linear relationships have been found between the Pauling electronegativity values for the halogen atoms and the observed vertical ionization energies corresponding to a₂ of a₂′ orbitals of CFX₃ and related compounds CHX₃, OPX₃, BX₃ and PX₃ (X = F, Cl, Br, I).     

The valence states of NO+

Spectroscopic constants for the eight lowest electronic states of the NO⁺ ion are tabulated. These constants result from reanalysis of previously reported optical and photoelectron spectra and interpolation from corresponding states of the isoelectronic molecules CO and N₂. Similar spin-orbit perturbations of the A¹Π states of NO⁺ and CO are compared. An interpretation is given of previously reported emission from a beam of long-lived states of NO⁺. The intensities of ionizing transitions from NO X²Π (v = 0) observed in photoelectron spectra are compared with calculated Franck-Condon factors.     

Photoelectron spectroscopy studies of the band structure of silver halides

X-ray photoelectron spectroscopy has been used to probe the valence bands of the silver halides. Previous ultraviolet photoemission and optical absorption experiments together with the theoretical band structure calculations form the basis for interpretation of the spectra. Density of states maxima from the halogen p levels are clearly resolved from those of the silver 4d states. Additional splittings due to k space symmetry are observable and in the case of AgCl and AgBr, give excellent conformation of existing band structure calculations. The role of spin-orbit coupling is shown to be unimportant in determining the primary shape of the photoelectron spectrum. The spectrum of AgF shows the inversion of silver 4d and halogen 2p levels suggested by the optical absorption spectra and predicted by several recent band calculations. A new interpretation is proposed for the AgF optical spectrum in which the observed excitons are due to the forbidden Γ₁₂→ Γ₁ and Γ_25′ → Γ₁ tr the high temperature body centered cubic structure. These spectra clearly show the broadening of the I 5p levels which causes the band gap to decrease above the transition temperature.     

Infrared Spectra of trans-nitrobis (2, 4-pentanediono) Aniline-Cobalt(III) Complexes

The infrared spectra of eighteen complexes of general formula trans-[Co(NO₂) (acac)₂ (R-C₆H₄NH₂)] (acac = acetylacetonate anion, R = 3- or 4-aniline substituent) are discussed. ¹⁵N-Labelling of the complexes containing aniline and p-toluidine yields assignments of the N-H, C-N and Co-N stretching frequencies and the N-H bending frequencies. These assignments receive support from the observed frequency shifts induced by varying the substituent R which also permits the assignment of the Co-o stretching frequencies.     

The electronic structures of some aromatic sulfinylamines

He(I) and He(II) photoelectron spectra of some sulfinylamines are reported and assignments made on the basis of CNDO/S LCAO MO calculations. Insight into the effects of several substituents on the electronic structures of the compounds is obtained. The difference between the actual electronic structure of o,o′, p-trimethyl sulfinylaniline and that interpolated from other molecules in the series is assumed to reflect a different conformation for this compound.The results of the MO calculations agree fairly well with the experimental data, although some discrepancies occur, concerning especially the π-donating capacity of a Cl substituent, and ionizations from chlorine lone pair orbitals.     

A photoelectron and energy-loss spectroscopy study of Ti and its interaction with H2, O2, N2 and NH3

A unified electron spectroscopic study of polycrystalline Ti and its interaction with H₂, O₂, N₂, and NH₃ are described. Auger electron spectroscopy (AES), electron energy-loss spectroscopy (ELS), ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS) are combined to provide detailed information about the electronic structure of the titanium surface and its interaction with these adsorbates. X-ray and ultraviolet photoelectron spectra and electron energy-loss spectra are presented for the clean titanium surface, and following exposure to H₂, O₂, N₂ and NH₃. Spectral assignments are provided in each case. The electron spectra of oxygen exposed Ti and nitrogen sputtered Ti are quite similar, and are interpreted with reference to band structure calculations for TiO and TiN. Electron spectroscopy indicates essentially complete dissociative adsorption of NH₃ on the clean titanium surface.     

The electronic structure,x-ray photoelectron and emission spectra of YOF

The results of electronic structure calculations for YOF are presented, making use of Xα-DVM together with experimental X-ray photoelectron and emission spectra for this compound. Three versions of calculations have been performed, depending on the relation between oxygen and fluorine charges in the [YO₄F₄] cluster. The interpretation of experimental spectra is carried out on the basis of these calculations.     

Spectroscopic studies of atmospheric interest on NO and NO

In recent years, high-resolution photoelectron spectroscopy and ab initio calculations have considerably revised and enlarged the understanding of the electronic structure of the NO and NO⁺ molecules. The experimental potential energy curves for the different electronic states of atmospheric interest molecules like NO and NO⁺ are constructed by using the Rydberg-Klein-Rees method as modified by Vanderslice et al. The ground state dissociation energies are determined by curve fitting technique using the five parameter Hulburt-Hirschfelder (H-H) function. The estimated dissociation energies are 6.381 and 10.693 eV for NO and NO⁺, respectively. These values are in good agreement with the literature values. The r-centroids and Franck-Condon factors (FC Factors) for the band system of B²Π_r-X²Π of NO and a³Σ⁺-X¹Σ⁺, A¹Π-X¹Σ⁺ of NO⁺ molecules have been calculated employing an approximate analytical methods of Jarmain and Fraser, and Nicholls and Jarmain. The absence of the bands in these systems is explained.     

XPS study of plutonium oxides

X - ray photoelectron spectra of core and valence levels are presented for PuO₂ and Pu suboxide. This suboxide with formula ～ Pu₂O₃ results either from the reduction of PuO₂ under argon bombardment of from oxidation of clean Pu metal. The valence band spectrum of PuO₂ is compared with relativistic molecular cluster calculations.     

B-, N-doped and BN codoped C60 heterofullerenes for environmental monitoring of NO and NO2: a DFT study

ABSTRACT

Using density functional theory calculations, we investigate the gas sensing performance of B-, N-doped and BN-codoped C₆₀ fullerenes towards NO and NO₂ molecules. The calculated adsorption energies and net charge-transfer values indicate that NO and NO₂ molecules have a stronger interaction with the BN-codoped fullerenes compared to the B- or N-doped ones. It is also found that the electronic properties of the BN-codoped C₆₀ exhibit a larger sensitivity towards NO and NO₂ molecules. An increase in the concentration of doped/co-doped B and N atoms tends to weaken the gas sensing ability of these systems.     

Ab initio calculation of the dipole moment of cyanamide

The He(I) photoelectron spectra of the isoelectronic series Fe(CO)₂(NO)₂, Co(CO)₃NO and Ni(CO)₄ are reported and interpreted by means of ab initio SCF-MO calculations. For the nitrosyl complexes it is found that ionization potentials calculated assuming Koopmans' theorem are seriously in error due to the considerably greater orbital relaxation accompanying ionization from metal than from NO valence orbitals. When such allowance is made for orbital relaxation by performing restricted Hartree-Fock (RHF) calculations on the ionic states, the experimental spectra are accurately reproduced and the observed similarity of the spectra of all three molecules is explained.     

Ab initio molecular orbital calculations of transition metal complexes

All electron ab initio SCF-MO calculations in a better-than-minimal basis of the electronic structures of Mn(CO)₅H, Mn(CO)₅CH₃, Mn(CO)₅Cl and Mn(CO)₅CN are reported. The nature of the bonding of the CO groups, and of the other ligand to the central metal atom is discussed, together with the effect of the substituent on the electronic structure of the carbonyl ligands. The calculated wavefunctions are used to discuss the low energy photoelectron spectra, and other experimental data on these molecules.     

Switching behavior induced by different substituents of group in single molecular device

We investigate the electronic transport properties of photochromic azobenzene-based molecular devices with Au electrodes using non-equilibrium Green’s function and density functional theory. A reversible switching behavior between cis and trans isomerization is found in the device. In addition, the substituent of ?NH₂ on the right end hydrogen atom of azobenzene molecule reduces the switching ratio of current, consequently the disappearance of switching behavior, while the substituent of ?NO₂ improves the switching ratio of current. We discuss the different electronic transport induced by different substituents through the transmission spectra, localized density of states, molecular projected self-consistent Hamiltonian and transmission pathways. The observed polarization effect under bias is explained by the evolution of molecular projected self-consistent Hamiltonian of LUMO level. The results indicate that the electron-withdrawing group ?NO₂ substituting right terminal hydrogen of azobenzene molecule becomes a candidate for improving the performance of molecular device.     

On the assignment of the carbon K-shell spectra of the methyl halides

Electron energy loss spectra of the methyl halides in the region of carbon K-shell excitation have been obtained at higher resolution than those previously reported. The existence of two electronic transitions between 288 and 290 eV in CH₃F is demonstrated. This result conflicts with a recent SCF calculation which suggests that the σ* (C–F) level in CH₃F is unbound and thus predicts the existence of only one electronic transition in this spectral region. Studies of the carbon K-shell spectra of CH₃Br and CD₃Br demonstrate the vibrational origin of some spectral features. These new results support our earlier tentative assignments for the carbon K-shell spectra of the methyl halides.     

X-ray photoelectron spectra of nickel halides: multiplet structure and multi-electron excitations in Ni2+ 3p and 2p shells

The satellite structure in the X-ray photoelectron spectra of nickel halides has been measured. The satellites found in the photoelectron spectra of Ni²⁺ 3p and 2p subshells have two common sources: multiples splitting and multi-electron excitations. The experimental spectra are compared with theoretical results on multiples splitting and with calculations of band structure.