共查询到20条相似文献,搜索用时 24 毫秒
1.
J. Grimblot J.P. Bonnelle J.P. Beaufils 《Journal of Electron Spectroscopy and Related Phenomena》1976,8(5):437-447
X-ray photoelectron spectra of the Co 2p, and Mo 3d levels for catalysts containing cobalt and molybdenum supported on alumina have been studied. Binding energies and relative peak areas have been investigated in detail in order to establish the formal metal oxidation states and environment of cobalt and molybdenum cations supported on alumina. Before a monolayer has been formed, only tetrahedric sites of alumina are occupied by Co2+ cations. After the monolayer has been formed, heterogeneous oxide Co3O4 appears. Both tetrahedral and octahedral sites of alumina are occupied by the molybdenum cation in the 6+ formal oxidation state. 相似文献
2.
DIeter Klapstein Jonhn P. Maier Martin Ochsner Werner Zanbach 《Journal of Electron Spectroscopy and Related Phenomena》1984,34(2):161-162
Rotationally cooled bromochloroacetylene cations have been studied in the ≈X2Πω and ≈A2Πω (ω = , ) states in the gas phase by two complementary spectroscopic techniques. The ≈A2Π ? ≈X2π band system was excited in emission by electron impact of a seeded supersonic helium free jet and as fluorescence by laser excitation of cations formed by Penning ionisation in a cooled environment. Comparison of the two sets of data locates the spin—orbit component bands and the origins of the systems, and allows the main spectral features to be vibronically assigned. The vibrational frequencies of most of the fundamentals are thus obtained to within ±2 cm?1 for this cation in both the states. 相似文献
3.
H. Sawatari E. Iguchi R.J.D. Tilley 《Journal of Physics and Chemistry of Solids》1982,43(12):1147-1155
The formation energies for the point defect species Ti4+ interstitials, Tii4+, and oxygen vacancies with an effective charge of + 2e, Vo2+, have been calculated using the polarisable point ion shell model. The formation energy of Tii4+ was found to be a 10.8 eV for occupation of the (0, , ) site. The energy of Tii4+ at other sites is somewhat higher than this figure, and allowed the migration energy of Tii4+ parallel to the c axis to be estimated as 2.9 eV. The formation energy of Vo2+ was found to be 10.1eV. The variation of these formation energies with dielectric constant was also calculated. It was found that the energy of formation of Tii4+ varied considerably with dielectric constant, while the formation energy of Vo2+ was almost independent of dielectric constant. The relevance of these results to the presence of crystallographic shear planes in reduced rutile is considered. 相似文献
4.
The ordering of the mobile ions in the conducting layers to form an superlattice has been investigated in K+, Ag+ and Rb+ β-aluminas by electron diffraction. In addition to the correlation of mobile ions within the conduction layer, the correlation between conduction layers has also been detected in Rb+ β-alumina with periods of 68.4 Å and 22.8 Å, or three and one multiple of the dimension. A possible mechanism for such long distance correlation through spinel blocks is discussed. 相似文献
5.
N.A. Rastrenenko V.A. Tyagai N.Ja. Chistyakova M.K. Sheinkman 《Solid State Communications》1981,38(5):393-395
The refractive index of PbO tetragonal single crystals () and parameters of thin dielectric film on their real surfaces (nf = 1.56±0.01, ) have been measured by the method of ellipsometry at . For the first time the photo-induced changes of optical properties of PbO(t) surface film have been observed. 相似文献
6.
S. Kumarakrishnan N.L. Peterson T.O. Mason 《Journal of Physics and Chemistry of Solids》1985,46(9):1007-1014
The diffusion of 48V in disordered VOx, crystals has been measured by a serial-sectioning technique as a function of temperature (1100–1500°C) over the homogeneity range 0.78 < x < 1.28. The temperature dependence of the cation tracer diffusivity at each fixed composition is characterized by an Arrhenius behavior in the temperature range 1100–1500°C. The Arrhenius parameters decrease rather sharply near the stoichiometric composition as the composition increases from the metal-rich to the metal-deficient regime; the activation energy for diffusion decreases from ~71 to ~48 , and the frequency factor decreases by nearly two orders of magnitude (from ~5 to ~0.05 . It is concluded that the significant difference in the cation self-diffusion behavior between the metal-rich and the metal-deficient VOx may be attributed to the significant differences in the defect structures of the two regimes. The various possible diffusion mechanisms are explored, and comparisons of the cation diffusion behavior in VOx, with that of the related transition-metal monoxides TiOx and Fe1?δO are made. It is concluded that the experimental results for the entire composition range are consistent with the process of diffusion occurring by the migration of monovacancies in equilibrium with defect clusters, the nature of the clusters being different for x < 1 and x #62;; 1. 相似文献
7.
A.N. Thorpe J.A. Minkin F.E. Senftle C. Alexander C. Briggs H.T. Evans G.L. Nord 《Journal of Physics and Chemistry of Solids》1977,38(2):115-123
X-Ray diffraction and anisotropic magnetic measurements have been made on single crystals of lunar ilmenite and on terrestrial ilmenite from Bancroft, Ontario, Canada and the Ilmen Mountains, U.S.S.R. The elongated -axis of lunar ilmenite, previously reported, is confirmed by new measurements. The shorter -axis found in terrestrial specimens is ascribed to Fe3+ substitution for Ti4+ in the titanium layer. Magnetic measurements on the same specimens show that, in agreement with the Ishikawa-Shirane et al. model, the initial shortening of the -axis by the above substitution of small amounts of Fe3+ (<8%) causes an increase in Fe2+?Fe2+ exchange coupling through Fe3+ in the titanium layer that lowers the Néel transition temperature. The Weiss temperatures and other magnetic parameters confirm this model proposed by Ishikawa and Shirane et al.Additional transitions found in one of the terrestrial specimens (Bancroft) have been ascribed to a small amount of an exsolved spinel phase, possibly a solid solution phase of magnetite-ülvospinel. The spinel phase is localized in hematite-rich blebs which exsolved from the host ilmenite-rich phase. 相似文献
8.
A Pd-rich phase has been observed to segregate on the surface of PdAg alloys under the influence of 500 eV Ar+ and N2+ bombardment. By examining the X-ray photoemission spectra of these surfaces, we report changes in the structure of the Pd 3d peaks which are specifically linked to this phase. Studies of the spectral changes with Ar+ dose show that one peak arises from electrons originating from the altered overlayer and a second peak arises from the underlying alloy with a binding energy dependent on the underlying concentration. The altered layer is found to vary in thickness between one and five layers, depending on the bulk alloy concentration. The thickness of this layer is also dependent on the nature of the primary ion since a different altered layer thickness is found using nitrogen ion bombardment. 相似文献
9.
The self-diffusion coefficient of 22Na+ and the ionic conductivity are measured as a function of temperature in NaCl single crystals doped with labelled yttrium ions, as well as the diffusion coefficient of 88Y3+. We give the theoretical equations for the transport processes in the alkali halides doped with a trivalent cation; These are derived from the theory of the crystals doped with divalent cations. Solubility of YCl3 in NaCl is accurately determined through a radioactive technique. The free enthalpy of solubility of free Y3+ is: (2.91?13 kT) eV. A good fit of the whole set of data is obtained by treating the association between Y3+ ions and vacancies by the single equation . The jump frequency of Y3+ is . The results are compared to those characterising the divalent foreign cations. 相似文献
10.
The 24Mg(13C, 12C)25Mg reaction has been studied at 30 MeV using a magnetic spectrometer. Differential cross sections for transitions to several final states in 25Mg have been measured and analysed using an exact finite range DWBA code. The DWBA predictions have fitted the bell-shaped distributions satisfactorily, yielding spectroscopic factors which are in reasonable agreement with those obtained using (d, p) reactions. The exceptions are the + state at 0.97 MeV which displays a marked departure from the bell-shaped angular distribution obtained for the other + state at 2.80 MeV, and the + state at 1.61 MeV whose angular distribution has an unusual shape, displaying a deep minimum located at the grazing angle. A semiquantitative model has been used to suggest that the angular distribution for the 0.97 MeV state is evidence for the coupling of inelastic processes in this transition. In the case of the 1.61 MeV state it is suggested that the angular distribution shows the influence of indirect Coulomb excitation on the transfer cross sections. 相似文献
11.
O.B. Ajayi L.E. Nagel I.D. Raistrick R.A. Huggins 《Journal of Physics and Chemistry of Solids》1976,37(2):167-172
Motional activation enthalpies have been calculated for interstitial cations in the rutile structure, using a minimum energy path approach. Coulombic, overlap repulsion and polarization energy terms were included in the potential energy expression. Preexponential factors in the overlap repulsion terms were evaluated by minimizing of the total electrostatic energy, and permanent dipole moments of the anion by an iterative method. The most favorable diffusion path was found to be parallel to the c-axis in the , 0, z direction in both TiO2 and MgF2.Motional activation enthalpies increased with increasing interstitial cation radius and were larger in TiO2 than in MgF2. The path was independent of radius and material. Strongly anisotropic conductivity was predicted for both compounds. 相似文献
12.
R.F. Davie A.R. Poletti G.D. Dracoulis A.P. Byrne C. Fahlander 《Nuclear Physics A》1984,430(2):454-484
The properties of high-spin states in 205At have been investigated to and an excitation energy of > 4.0 MeV. The properties of the + isomer at 2340 keV have been established and those of the + isomer at 2063 keV have been further investigated. In the present study the mean lives of these isomers have been determined as 11.2±0.2μs and 98±2 ns respectively. The M2 branch of the + state at 970 keV to the + ground state has been measured. This decay is attributed to a proton single-particle transition. The trend of excitation energies of a number of proton excitations in the odd-mass nuclei from 211At to 201At has been compared to the corepolarization model and the average interaction energy has been deduced. Comments are made upon probable configurations for many of the levels. 相似文献
13.
Taking into consideration the effective potential and the magnetic field dependent dielectric function, the effective g-factor and the magnetic susceptibility have been calculated. Results show that both quantities oscillate with magnetic field.The amplitude of the effective g-factor found in this way has the value between 3.26 and 2.49 for surface electron densities n ranging from 1.0×1012 to 7.0×1012 cm-2. The enhancement of g-factor is divided into two parts, noninteracting and interacting part. The interacting part is dominant and shows behavior. 相似文献
14.
M. Deutschmann G. Otter H. Böttcher H.J. Schreiber V.T. Cocconi G. Kellner D.J. Kocher D.R.O. Morrison H. Saarikko K.L. Wernhard D. Kuhn R.M. Eason B. Pollock F. Mandl M. Markytan 《Physics letters. [Part B]》1978,73(1):96-98
A total of 101 ω? decays have been found in K?p interactions at 10 and . The decay angular distribution has been fitted under the assumptions that the ω? has spin either . It has been found that the probability of isotropy (spin is less than one in a thousand, whereas the probability for spin is about 70%. Thus, we exclude the spin assignment. The lifetime of the ω? is found to be (1.41?0.24+0.15) × 10?10s, in agreement with our earlier result based on about of the present sample. 相似文献
15.
Z. Burshtein A.W. Hansom C.F. Ingold D.F. Williams 《Journal of Physics and Chemistry of Solids》1978,39(10):1125-1131
Hole drift mobilities have been measured in β-9,10 dichloroanthracene by the transient photoconductivity method. Mobilities were found to be isotropic in the ac plane, 0.6 cm2/V sec, and 0.18 cm2/V sec normal to this plane, b1, at room temperature. At lower temperatures the mobilities were thermally activated, with an activation energy of ~0.25eV. The crystal structure of β-9,10 dichloroanthracene has been determined; it is triclinic. , , , . The influence of the crystal structures of the α- and β- forms on the intermolecular electronic overlap and hence carrier mobilities are discussed. 相似文献
16.
G. Beyer A. Jasiński O. Knotek H.-G. Ortlepp H.-U. Siebert R. Arlt E. Herrmann G. Musiol H. Tyrroff 《Nuclear Physics A》1976,260(2):269-286
Radioactive sources of 123, 125, 127, 129Ba obtained in the spallation reaction have been studied with Ge(Li), Si(Li), NaI(Tl) and plastic detectors. On the basis of γ-ray energies, intensities, energy sums and coincidence information, the decay scheme has been proposed for 127Ba. No high-spin isomer of 127Ba has been observed. The lifetimes of + → + transitions in 123, 125, 127, 129Cs have been measured. No evidence for the shape isomerism in 127Cs has been found. 相似文献
17.
J. Treherne J. Genevey R. Beraud A. Charvet R. Duffait M. Meyer F.A. Beck T. Byrski 《Nuclear Physics A》1980,342(2):357-372
Excited states of 103Ag have been investigated in the 94Mo(12C, p2nγ)103Ag reaction and observed up to 6414 keV excitation energy. A perturbed band based on the 27.6 keV + intrinsic state has been strongly populated up to spin +. In addition, two negative-parity bands with spins ranging from ? to at least ? were also observed. An interpretation of the experimental results is proposed in the framework of the axial-symmetric rotor-plus-particle model using deformed self-consistent quasi-particle states. 相似文献
18.
Y.C. Cheng 《Surface science》1973,40(2):433-438
The adsorption of oxygen on clean cleaved (111) silicon surfaces has been investigated by high resolution electron spectroscopy (HRES), Auger electron spectroscopy (AES) and ellipsometry. Localized vibrations (, 130 and 175 meV) which are related to the binding state band of oxygen are identified with HRES. AES measures the concentration of adsorbed atoms basically independent of their binding state while ellipsometry refers additionally to the optical properties of the adsorbed layer. The same adsorption kinetics was found with the three methods. Oxygen therefore adsorbs in a single likely molecular state. The sticking coefficient S increases exponentially with the surface step concentration. S is also enhanced by the presence of nude ion gauges. Depending on these parameters sticking coefficients between 2 × 10?4 and 10?1 have been obtained. This result might contribute to an explanation of the large differences in earlier works. 相似文献
19.
During investigations of anti-Stokes effects in erbium—ytterbium doped yttrium oxysulphide phosphors we have found an excitation of the erbium green emission due to 810 nm radiation (4I → 4I transition), the effect being of a two-photon type. There is also a two-photon excited blue emission (2H → 4I transition) due to the same radiation. Introduction of ytterbium impurity has a deleterious effect on the above 810 nm excitation, in contrast to its sensitization of the 1000 nm anti-Stokes excitation. To distinguish between various excitation schemes a two-beam excitation technique has been used. Results show that ytterbium inclusions lead to loss of energy from the 810 nm excitation by increasing the probability of downward transitions from the 4F level to 4I and 4I states, reached after onephoton absorption. This effect is indicated by an increase in 1500 nm emission (4I → 4I with ytterbium concentration. 相似文献
20.
The γ-ray spectrum from the 176Lu(n, γ)177Lu reaction has been investigated in the energy range 450 to 1420 keV using a newly developed gamma band-filter spectrometer. A total of 153 transitions have been observed. Improvements to the 177Lu scheme are suggested, and in particular the γ-decay of several levels of the ?[530↑] and ?[532↓] rotational bands is proposed. Special attention has been given to the Coriolis coupling between the two latter bands and the ?[541↓] band. Results on a complementary investigation of the 175Lu(n, γ)176Lu reaction are presented. 相似文献