F. Al-Adel

XPS, auger, electrical and optical studies of vanadium phosphate glasses doped with nickel oxide☆

Abstract X-ray photoelectron and X-ray excited Auger spectra, optical absorption and DC conductivity of vanadium phosphate glasses containing nickel oxide have been studied as a function of nickel content. The shift in the binding energy of the V 2 p 3 2 photoelectron peak with the change in nickel content provided evidence of a change in the valence states of vanadium. The Ni 2 p 3 2 core level in NiO powder is a doublet and is normally used as a fingerprint for NiO. However, a single peak, shifted to higher binding energy, was observed in the glasses. The Ni (LVV) Auger spectrum for NiO powder showed a doublet structure. In glasses, however, two well-separated peak were observed in this spectrum. The results suggest that Ni in the glass may exist in two different phases, viz. nickel oxide and nickel vanadate. Initial addition of nickel (2 wt% of NiO) increased the optical absorption and electric conductivity but large additions, (5 wt% of NiO) led to a small decrease. The conductivity had a minimum value for a concentration of about 10 wt% of NiO. An attempt has been made to account for the observed changes in optical and electrical properties in terms of the XPS and Auger results.

X-ray photoelectron spectroscopy and Fourier transform-infrared studies of transition metal phosphate glasses

X-ray photoelectron spectroscopy and Fourier transform-infrared studies were carried out on phosphate glasses containing oxides of iron, cobalt, nickel, copper and zinc. The results suggest that the glasses containing iron and zinc may have structures in which both the phosphorus and the iron (or zinc) atoms are tetrahedrally coordinated by oxygen into three-dimensional structures which resemble the polymorphic forms of silica, whereas the glasses containing cobalt, nickel and copper may consist of polymeric chains of PO4 tetrahedra bonded to adjacent tetrahedra via bridging oxygens. These polyphosphate chains are linked together by the interaction between the metal cation and the oxygens of the network former. In addition, the core level 2p shake-up satellites of the 3d-transition metal ions in these glasses were studied. The results support a suggestion that the satellites in the glass are most likely due to the electron transfer from ligand to metal 3d orbitals.

Determination of the radiative lifetimes of nine ion-pair states of I2

Abstract The radiative lifetimes of 9 out of the 20 possible ion-pair states of I2 have been measured using two-colour optical-optical double-resonance excitation. A pulse-shortened dye laser was used to populate the final state. Lifetimes for all six states in the first cluster - δ(2u), γ(1u), D(0u+), D′(2g) β(1g) and E(0g+) - have been measured again in view of the often d literature values. The lifetimes of three states in the second ion-pair cluster (H(1u), F(0u+) and f(0g+)) are reported for the fir time. No significant pressure dependence was found up to 100 m Torr, with the exception of the longest lived γ state.

Unexpectedly rich vibronic structure in supersonic jet spectra of sulfur dioxide between 360 and 308 nm

Abstract An extensive vibrational resolution study of SO2 between 27780 and 32500 cm−1, spanning absorption to the 3B1, 1A2, and 1B1 electronic states, has been carried out via fluorescence excitation in a molecular beam, achieving substantial improvements in sensitivity and rotational cooling over previous studies. Characterization of the dependence of transition intensities on molecular beam conditions has been used to identify and separate the contributions of cold and hot transitions in the spectra. Vibrational-mode-selective, carrier-gas-dependent cooling is observed and is instrumental in the identification of a group of vibrational levels exhibiting novel Franck-Condon patterns and little or no cold absorption. At least 135 vibronic levels are identified in the energy range studied, adding 71 to the previous total reported from our own and other laboratories. Eight levels below 29000 cm−1 are assigned to the 3B1 electronic state, supported by a set of anharmonic constants to approximate the observed vibrational structure. In the higher energy region, the accepted two-singlet-electronic-state model is compared to the experimental results and shown to be inadequate to account for the large number of observed levels.

Study of the Lorentz-Lorenz law and the energy loss of 4He ions in titanium oxide films

The optical constants, thicknesses and densities of thin titanium oxide films, deposited by electron beam evaporation, were measured. The variation of the refractive index with the density, of titanium oxide samples in the form of thin films (present work) and bulk crystalline form (data from the literature), was observed to follow the Lorentz-Lorenz law. The molecular electronic polarizability deduced from the law was close (within the uncertainty in the measurement) to the value reported in the literature. Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy studies were carried out on the thin films.

Vibrational structure in the low energy region of the 1A2 state of SO2

Abstract Molecular beam fluorescence excitation spectra of sulphur dioxide in the wavelength range 348—334 nm are presented. Identification of cold transitions is accomplished by controlled variation of vibrational temperature, and narrow rotational contours permit accurate determination of the corresponding vibrational band origins. These data conform well with the proposed assignment of 1 A 2 — 1 A 1 vibrational progressions of Hamada and Merer, although different progressions are found to display markedly different intervals. The energy below which bands of the 3 B 1 — 1 A 1 transition exceed those of the 1 A 2 — 1 A 1 system in intensity is found near 347 nm.

Laser-induced fluorescence of selectively excited bands located within the E band's spectral range of SO2

Abstract An attempt to investigate the vibrational bands near the origin of the E band of SO 2 has been made in a supersonic jet experiment. Several cold vibrational bands have been identified within the 32850–32880 cm −1 region and their fluorescence spectra have been selectively excited and measured. A hot band activity at ≈ 32872 cm −1 was found to persist at low rotational temperatures, which caused the Frank-Condon intensity pattern of the E bands fluorescence spectrum to vary when measured under slightly different cooling conditions. The bands upper levels were not all found to have the same vibronic symmetry as that of the E band.

Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy studies of thin glass films prepared by laser evaporation

Abstract Multicomponent glass and laser-evaporated thin films prepared from the glass were studied by Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy. The composition of the glass and the film as determined through RBS suggested that the films were deficient in oxygen. Furthermore, an increase in the reduced states of vanadium ions in going from the glass to the film was detected from the shift in the binding energy of the core level peak of V 2p and the development of a component peak in the V L3M23V Auger spectra. The reduction of vanadium could have possibly occurred because of the loss of oxygen during evaporation and thus would support the RBS results.

Laser‐produced reduction of pentavalent vanadium in aqueous solutions and V2O5 powder

The reduction of pentavalent vanadium ions in aqueous solutions upon laser irradiation has been confirmed by using optical absorption and fluorescence techniques. X‐ray photoelectron spectroscopy (XPS) study revealed that V2O5 was reduced to lower oxides upon laser treatment. Furthermore, the presence of reduced valence states of vanadium has been detected through XPS in vanadium‐containing solids such as V2O5/P2O5 glass, thin films prepared separately from V2O5 powder and the glass.

Zero-order 1B1(n,0,0) vibrational levels of sulfur dioxide

More than 100 single vibronic level fluorescence spectra of SO2 throughout the 30 400–34 230 cm−1 spectral region were selectively excited and recorded in crossed supersonic jet and laser beams under conditions of cold rotational temperatures. It was found that the vibronic origins can be grouped into 5 overlapping regions based on identical Franck–Condon patterns of the X 1A1(n,0,0) progressions. The spacing between the centers of these regions was found to range between 572 cm−1 and 647 cm−1 as opposed to the previously estimated value of 690 cm−1. The onset of the 1B1 state in the vibronic coupling was found to be at the 30 553 cm−1 band, which is below the previously reported threshold energy by 220 cm−1. The results provide qualitative verification of the multilevel coupling mechanism proposed by Kullmer and Demtroder [Chem. Phys. 92, 423 (1985)].