A SCF Xα MO study of the optical and Ti2p core photoemission spectra of TiCl4

SCF Xα MO calculations on the ground state and optical excitation transition states of TiCl₄ accurately predict the energies of its UV absorption peaks. Calculations on the Ti2p core ion state and associated transition states indicate that the recently observed low energy (4.0 eV) Ti2p satellite arises from ligand to metal charge transfer excitations while the satellite at high energy (9.4 eV), similar to those previously observed in Ti(IV) compounds, can be attributed to transitions from the highest filled orbitals to empty orbitals with Cl3pTi4s. 4p antibonding character.     

A study of shake-up satellites in Co 2p photoelectron spectra of trans-[Co(NH3)4Cl2]Cl and cis-[Co(NH3)4Cl2]Cl isomers

Mg Kα X-ray photoelectron (ESCA) spectra of the Co 2p levels have been obtained in trans- and cis-[Co(NH₃)₄Cl₂]Cl isomers. It is observed that these compounds slowly decompose under X-ray irradiation. A procedure is employed to record real spectra for both the trans and cis isomers without any significant complication by the decomposition products. Three satellites are observed in both spectra at binding energies ≈ 4.8 eV, ≈ 9.3 eV, and ≈ 16.5 eV greater than that of the Co 2p_{$\text{3}\text{2}$} peak. These isomers are distinguished from one another by the sizable difference in the relative intensity of the first satellite to the main peak. The first two satellites are assigned to ligand to Co 3d shake-up transitions by use of symmetry arguments based on molecular orbital theory, while the origin of the third satellite is less certain. The implication of the results is discussed.     

HeI photoelectron spectroscopic study of the electronic structure of SSF2 and FSSF compounds

HeI photoelectron (PE) spectra are re-recorded for SSF₂ and FSSF. The assignment of bands has been made with the aid of band shapes, band intensities and ab initio calculations. In the PE spectrum of SSF₂, two sharp peaks at 10.48 and 11.22 eV are considered to result from through-space interaction of lone-pair orbitals in the two S atoms and two sharp peaks at 12.50 and 12.90 eV from through-space interaction of lone-pair orbitals in the two F atoms. The larger splitting of the S atoms can be attributed to the larger 3p orbital of S. The lack of sharp peaks in the PE spectrum of FSSF shows that there is no orbital which embodies the character of a lone-pair. So the PE spectra of SSF₂ and FSSF are examples embodying through-space interaction of lone-pair orbitals.     

Ab initio configuration interaction calculations of the NIs (NO2) core-hole states of p-nitroaniline

The NIs (NO₂) core-hole states of p-nitroaniline are calculated by a Cl procedure that takes account of both orbital relaxation and correlation effects. A satellite peak arising from the excitation 4b₁(Π) → 5b₁(Π) is calculated to occur 26 eV from the main ionization peak, with a relative intensity of 66%. These results are compared with gas-phase photoelectron spectra.     

X-ray photoelectron spectra of Ti4+ in TiO2. Evidence of band structure

Satellite structure has been observed at about 3.1, 5.4, 6.4 and 14.5 eV below the main peaks in the X-ray photoelectron spectra of the Ti and O levels of TiO₂. These satellites arise from transitions, accompanying primary photoemission, between predominantly O_2p states of the ligand and various excited states in the conduction band. The energies found fit the transitions calculated by Daude et al. for an electronic band structure calculated by a combined tight-binding and pseudopotential method.     

Energy-loss studies on ion-pair formation reactions for the K + NO2 system

The energy loss spectra of K⁺ ions produced in fast potassium atom—NO₂ molecule collisions were studied over the collision energy region 10–40 eV. The energy loss spectra for the K + NO₂ system showed five peaks. The first two peaks at about 3.0 eV are ascribed to the ground-states NO^?₂ with vibrational excitation. The remaining three peaks are ascribed to the electronically excited states of NO^?₂.     

Differential cross section for CN− formation from dissociative electron attachment to the cyanogen molecule C2N2

The differential cross section for CN^? formaition from dissoiiativc attachment on C₂N₂ has been obtained in a crossed-beam experiment. Below 10 eV incident electron energy thc CN^? cross section shows two broad overlapping peaks with maxima at 5.4 and 7.3 eV corresponding to the formation of CN^? in its ground electronic state ¹σ⁺ plus the CN radical in the first excited state²π and the ground stale ²Σ+ respcctively     

Photoionization study of Hg2

Photoionization efficiency data for Hg₂⁺ have been obtained in the region of 650–1400 A. The ionization energy of Hg₂ was determined to be 9.103 ± 0.010 eV. This value allows the calculation of the dissociation energy of Hg⁺₂ to be 1.40 ± 0.02 eV. By analyzing the differences in energy between corresponding autoionization peaks observed in the Hg⁺ and the Hg₂⁺ spectra and by assuming the charge induced-dipole interaction to be the dominant interaction between Hg⁺(²D_{5/2, 3/2}) and Hg at the equilibrium bond distance of Hg₂, the equilibrium bond distance for Hg₂ was deduced to 3.35 A.     

The ground-state potential curve for F2

The ground-state potential curve for F₂ has been obtained using large-scale MC SCF and CI methods. MC SCF curves were obtained with the CAS SCF method using a variety of sets of active orbitals. The main conclusion from the CAS SCF calculations is that the 2π_u orbital is important. CI curves were obtained using the contracted CI method. The largest calculations contained 312000 configurations proper spin and space (d_2h) symmetry. The main conclusions from the CI calculations are that the configuration XXX are important, otherwise errors in D_e of 0.3 eV and in r_e of 0.02 Å are found. The remaining errors at the CI level are 0.08 eV for D_e, 0.005 Å for r_e and less than 10 cm^?1 for the lowest vibrational levels.     

Measurements of differential cross sections for vibrational quantum transitions in scattering of Li+ on H2

A pulsed monoenergetic ⁷Li⁺ ion beam (lab. energy 10–40 eV) is scattered from a highly collimated (= 1.5°) H₂ nozzle beam. The time-of-flight spectrum of the ions scattered in the forward laboratory direction shows both a fast peak corresponding to forward center-of-mass scattering and a slow peak corresponding to wide-angle center-of-mass scattering. These peaks have been further resolved to show contributions from individual vibrational quantum transitions. From an analysis of the time-of flight spectra the differential inelastic cross sections for a wide range of angles and energies between 2 eV <E_cm < 9 eV have been determined. The spectra also contain information on rotational inelastic cross sections.     

Charge transfer shake-up satellites in X-ray photoelectron spectra of solid compounds of 3d0 ions

Satellite structure has been observed at 8 eV and 12 eV below the main metal 2p peaks for compounds of Sc³⁺ and Ti⁴⁺. These features are attributed to charge transfer “shake-up”: transitions (t_2g → t_2g^* and e_g → e_g^* respectively). The 8 eV satellites are only found in sulphate complexes of Sc³⁺. This is the first observation of satellites which are probably due to t_2g → t_2g^* monopole charge transfer transitions. The probability for this transition is usually low, resulting in the observation of satellites due to the e_g → e_g transition.     

Control-Growth and Photocatalytic Activities of Low-Dimensional Bi2Fe4O9 Crystals

Low-dimensional Bi₂Fe₄O₉ nanosheets and microrods have been selectively prepared by a solvothermal method, from which the growth of the Bi₂Fe₄O₉ crystals can be controlled by the variation of reaction conditions. Structure determination showed that the nanosheets are mainly exposed by {001} facets while the microrods are exposed by {110} facets. Ab- sorption spectra revealed that there are two bandgaps observed for both nanosheets (at 1.9 and 1.55 eV) and microrods (1.7 and 1.45 eV), and they both would be available for the sunlight photocatalysis e ciently due to the intensive absorption ability in a wide region. Photocatalytic investigation demonstrated that the overall photocatalytic performance of the microrods is prior to that of the nanosheets due to the variation of bandgaps and exposed facets. The present report provides a useful alternative strategy for the controlling growth of nanostructures and/or microcrystals besides the present demonstration of the Bi₂Fe₄O₉ crystals with diflerent bandgaps and facets that would be able to tune the corresponding photocatalytic ability selectively.     

Laser-induced fluorescence measurement of the nascent rotational distribution of N+2 (X2Σ+g) formed by electron impact on N2

The internal state distribution of ground state N⁺₂ ions formed from N₂ by electron impact ionization is measured under collision-free conditions using laser-induced fluorescence. Analysis of the B–X (0, 0) band shows the rotational distribution to be characterized by a temperature which increases slightly with decreasing electron energy (60–100 eV). Cascade contributions are unimportant.     

Transport and optical properties of heavily hole-doped semiconductors BaCu2Se2 and BaCu2Te2

Experimental and theoretical studies of the electronic and optical properties of orthorhombic BaCu₂Se₂ and BaCu₂Te₂ are reported. Experimental data include the electrical resistivity, Hall coefficient, Seebeck coefficient, thermal conductivity, and lattice constants for , and optical transmission and diffuse reflectance data at room temperature. Nominally stoichiometric, polycrystalline samples form with hole concentrations inferred from Hall measurements of 2×10¹⁸ and 5×10¹⁹ cm⁻³ near room temperature for the selenide and telluride, respectively. The corresponding mobilities are near 15 cm² V⁻¹ s⁻¹ for both materials. Optical measurements reveal a transition near 1.8 eV in BaCu₂Se₂, while no similar feature was observed for BaCu₂Te₂. First principles calculations indicate both materials are direct or nearly direct gap semiconductors with calculated gaps near 1.0 eV and 1.3 eV for the telluride and selenide, respectively, and predict weak absorption below about 2 eV. Transport properties calculated from the electronic structure are also presented.     

Translational energy distribution of excited deuterium atoms produced by controlled electron impact on D2

The Balmer-β line of the excited deuterium atom [D*(n = 4)] produced in e—D₂ collisions has been measured at high resolution (0.029–0.033 Å) and at various electron energies (17–100 eV). The translational energy distribution of D*(n = 4) has been calculated from analysis of its Doppler line shape. The distribution of D* has three major components as in the case of H*(n = 4) from H₂ reported in our previous paper. Their peaks lie at about 0, 6 and 8 eV. The excitation function of D* is found to have two thresholds at 17.4 and 26.4 eV. The second component of D* has a larger translational energy and a higher threshold than those of the corresponding component of H*. These results indicate that the contribution from the lowest doubly excited state, ¹Σ_g⁺(2pσ_u)², is much smaller for D₂ than that for H₂.     

Evidence for the distortion of C2H4 and C2H2 chemisorbed on W(100)

The adsorption of C₂H₄ on W(100) has been studied by ultraviolet photoelectron spectroscopy with hν = 21.22 eV. The spectrum measured after in initial saturation exposure at 80 K exhibits structure which correlates well with energy levels recently calculated by Demuth and Eastman (DE) for sp³ rehybridized C₂H₄. Dehydrogenation of the adsorbate, either by subsequent heating to 295 K or direct adsorption at 295 K, yields a spectrum which correlates with DE's calculation for sp² rehybridized C₂H₂. These results suggest that C₂H₄ and C₂H₂ may be distorted from their planar and linear structures respectively and that the CC bonds on these molecules are stretched by adsorption on W(100). Qualitative arguments suggest that the bonding site for both melecules is directly over a W atom and that the Dewar—Chatt model for πd bonding in organometallic compounds is applicable.     

Preparation and comparison of the photoelectronic properties of Sr2Nb2O7 and Ba0.5Sr0.5Nb2O6

The two alkaline earth niobates Sr₂Nb₂O₇ and Ba_0.5Sr_0.5Nb₂O₆ have been prepared, their electronic properties measured, and their photoresponses compared. The indirect band gap in Sr₂Nb₂O₇ is 3.86 eV compared with 3.38 eV for Ba_0.5Sr_0.5Nb₂O₆. Hence, photoanodes composed of Sr₂Nb₂O₇ respond to much less of the “white” light spectrum than those made from Ba_0.5Sr_0.5Nb₂O₆. Nevertheless, their electrical outputs at an anode potential of 0.8 eV with respect to SCE in 0.2 M sodium acetate under “white” xenon arc irradiation of 1.25 W/cm² are comparable.     

UV photoelectron spectroscopy of matrix-isolated and condensed CO and N2

UV photoelectron spectra of matrix-isolated and condensed CO and N₂ have been measured. The emission from the 4σ, 1π and 5σ orbitals show similar relaxation shifts of about 1 eV. This shift is 0.3 eV larger for the species isolated in xenon matrices. The width of the peaks is smaller by 0.3 eV in the Xe matrix in comparison with the pure solids but remains larger than those measured for the gas phase.     

Electronic properties of semiconducting Cd2GeO4

Cd₂GeO₄ has been prepared from CdO and GeO₂ by solid state reaction at 850°C as a low resistivity (? ? 1 Ω · cm) n-type semiconductor. Its conductivity is increased by doping with trivalent metal ions and decreased by heating oxygen. The electrons originate from shallow donors and their mobility is determined by a combination of large polaron formation and impurity scattering. From photoelectrolysis data the band gap is determined to be indirect, at 3.15 eV; the first direct transition occurs at 4.1 eV. The relations between conditions of preparation, defect structure, and carrier concentration have been examined, but the available data do not allow an unambiguous identification of the nature of the donor center.     

Ionic conductivity in KCl-doped polycrystalline SrCl2

Conductivity studies on polycrystalline SrCl₂ doped with KCl have been carried out. The results are in substantial agreement with published results for single crystal work on SrCl₂, the activation energies being 1.8 eV for the intrinsic region, 0.35 eV for the extrinsic region, and 0.45 eV for the regions in which association of defects occurs. Most significant was the discovery of metastable electrolytes (4–5 mole% KCl in SrCl₂) having a conductivity of 1 × 10^?6 ohm^?1 cm^?1 at room temperature. These supersaturated solutions could be heat cycled up to 72°C, and they retained their initial conductivity after storage for 6 months at room temperature. This indicates that the equilibrium solubility of a dopant is not necessarily the limiting factor for extrinsic conductance in a solid material.