Far U.V. absorption spectra of manganese halides between 20 and 67 eV.

The absorption spectra of evaporated thin films of MnF₂, MnCl₂, MnBr₂ have been measured in the energy range 20–67 eV. The onset of the absorption of 3p Mn²⁺ is about 50 eV. At lower energies, the structures may be attributed to transitions from 2s F^-, 4s Br^- and 3d Mn²⁺ levels.     

UV absorption of RbAg4I5-RE (Sm, Yb) thin-film systems

UV spectra of samples prepared by vacuum deposition of Sm and Yb thin films on 100–200-nm thick films of the RbAg₄I₅ solid electrolyte (SE) at 300–350 K contain strong absorption bands peaking at about 4.3 and 5.0 eV. After deposition of ～5 nm of Sm, the ionic conductivity σ of the samples decreases from σ ₀ to ≈0.9 σ ₀, and the SE lattice parameter, from 11.24 to ≈11.15 Å, with the x-ray reflection halfwidth increasing from 0.5 to 0.8°. Further growth of Sm concentration in the samples changes the x-ray diffraction pattern, the absorption at 4.3 and 5.0 eV increases, a new absorption edge forms at 3.8 eV, and σ decreases down to ～10^?2 σ ₀. It is conjectured that the strong UV absorption bands in heavily defected silver halides of the RbAg₄I₅-Sm(Yb) system is genetically related to the 4d ¹⁰→4d ⁹5s electronic transitions in free Ag⁺ ions.     

Electronic structure of PbI2 from photoelectron spectra and the exciton problem

The valence band density of states for PbI₂ is determined from X-ray and u.v. induced photoelectron spectra. It is shown that the band derived from Pb 6s states is at 8 eV binding energy and not at the top of the valence bands as suggested by band structure and charge density calculations. A rigid shift in the predominantly iodine 5p derived bands to lower binding energy brings the band structure calculations into essential agreement with experiment. Pb 5d core level binding energies determined here are used to derive core level exciton energies of 0.7 eV from published reflectivity spectra.     

Electroreflectance observation of localized and itinerant electron states in NiO

We have observed electroreflectance spectra in NiO at 6 eV which we believe represent transitions from the oxygen 2_p derived valence band to the nickel 4s derived conduction band. We also observe the spectrum seen earlier by McNatt near 4 eV but interpret it differently in terms of transitions from the localized 3d⁸ state to the 4s band. These interpretations are consistent with the recent model of Adler and Feinleib.     

Electronic structure of the valence bands of H2-, Mg- and Pt-phthalocyanine derived from soft X-ray emission and photoelectron emission spectra

The soft X-ray emission and photoelectron emission spectra of H₂-, Mg- and Pt- phthalocyanine (PC) obtained using synchrotron radiation are reported and compared. In this way, an overall view of the pattern of valence bands is obtained and the electronic structure determined in terms of the component partial densities of states. In particular, from the valence p → 1s carbon and nitrogen K-emission spectra we determine for all three compounds the C and N 2p-like valence-band density of states with strong maxima located at binding energies of 8, 11 and 13.5 eV (carbon 2p) and 8 eV (nitrogen 2p) below the vacuum level. For PtPC the partial density of d-like valence states is determined from photoelectron emission difference-spectra and compared to previous XPS results. The sharp (1.2 eV FWHM) maximum of the Pt-derived partial density of states, observed at 6.9 eV binding energy, is assigned to the ⁴F term of a 5d⁸6s final-state configuration. A second, broader maximum at around 9.5 eV binding energy contains contributions from other terms of this 5d⁸ configuration, as well as from a 5d⁷ satellite (shake-up multiplet).     

Kβ2 X-ray emission bands of Ga and As and their compounds

Ga and As Kβ₂ emission bands of the compounds under study consist of a more or less pronounced Kβ₂ main band, a short-wavelength side band which according to calculations by the ‘sudden approximation’ method may be essentially assigned to a KM_IV,V → M_IV,VN_II,III satellite, and long-wavelength 3d → 1s bands. Compounds such as Ga₂(SO₄)₃, Ga(NO₃)₃, Ga₂O₃, NaH₂AsO₄, K₃AsO₄, and As₂O₃ also show long-wavelength side-maxima at a distance of about 12 and 15 eV, respectively, from the main band, which are due to electron transitions from bands or levels with a preponderant 0 2s character.The Kβ₂ main band of A^IIIB^V compounds is less pronounced owing to the widths of the K levels and to instrumental distortions. The distance between the maxima of the state density of the upper valence bands can be recognized only by a shoulder or asymmetry of the band at the long-wavelength side. By calculation of the Ga and As Kβ₂ bands in GaAs with a pseudopotential kp band structure method, and allowing for the influence of both the transition probability and instrumental distortion excellent agreement with experiment is obtained.     

3s- and 3p-core level excitations in 3d-transition metal oxides from electron-energy-loss spectroscopy

3s- and 3p-core level excitations for a large number of 3d-transition metal oxides, with a formal 3d occupation from 3d⁰ to 3d¹⁰, have been measured by electron energy loss spectroscopy in reflection geometry (REELS) with primary energies 200 eV≤E ₀≤1600 eV. Their intensities decrease systematically with the formal 3d-count, classifying them as transitions to empty 3d-states. The structure of the 3s excitations is analysed in detail and is compared to the 3s-XPS photoemission spectra of the samples. This 3s-REELS structure and its change with the 3d occupation can be explained by the assumption that the excitation arises mainly from a 3s²3dⁿ→3s¹3dⁿ⁺¹ quadrupole transition.     

Improved infrared and visible emission spectra of the H3 and D3 molecules

Better-resolved Rydberg-Rydberg emission spectra of the neutral H₃ and D₃ molecules in the infrared and visible regions, with less interference from H₂ and D₂ emission, have been obtained by using a Droege-Engelking type of corona discharge source. Using nl_λ notation, the lower electronic states are 3p₁ in the infrared and 2p₀ in the visible, and the upper electronic states are mixed (3s,3p₀,3d₀,3d₁,3d₂) states. In particular, a line near 16 842 cm⁻¹ in H₃, previously obscured by an H₂ line, reveals a (3s,3d) interaction that is confirmed by other lines. The spectra are analysed including this interaction. However, fits to effective Hamiltonians still have relatively large standard deviations, probably partly due to poor convergence of the rotational expansions and partly due to many small perturbations of the levels by background states.     

Photoluminescence of concentration series of CaF2: Mn phosphors excited by VUV radiation

Fluorescent characteristics of a series of powder CaF₂: Mn phosphors (from 0.01 to 2.47 wt. % of Mn in the mixture) excited by VUV radiation with quantum energies up to 14 eV at 293 K and up to 12 eV at 85 K are measured. Narrow excitation bands of Mn²⁺ centers found at 7.9 and 8.6 eV (at 293 K) are assigned to partially forbidden transitions of electrons from the ground state ⁶ S split by the crystalline field (10 Dq=0.71 eV from the literature) in two sublevels to the excited level corresponding to the ⁶ D term of a free Mn²⁺ ion (3d ⁵ → 3d ⁴4s transitions). A wide nonelementary excitation band in the region of 9.1–10.3 eV is interpreted as photogeneration of near-activator D-excitations: allowed transitions of electrons from levels that are split from the top of the valence band under the influence of an impurity ion to the free 4s-orbital of a Mn²⁺ ion. Channels of energy transport in the CaF₂: Mn system are briefly analyzed.     

The 4d-4f dipole resonance of the Pr atom in an endohedral metallofullerene, Pr@C82

The photoion yield spectra of an endohedral metallofullerene Pr@C₈₂ were measured in the photon energy range of 100-150 eV by using time-of-flight mass spectrometry. Parent ions Pr@C₈₂⁺, Pr@C₈₂²⁺ and Pr@C₈₂³⁺ were observed in the mass spectra. The photoion yield spectra of Pr@C₈₂²⁺ showed a broad peak at 120-140 eV that was assigned to the 4d-4f giant dipole resonance of the encapsulated Pr atoms. Absolute photoabsorption cross sections of Pr@C₈₂ were evaluated from the photoion yield spectra to be 37±12 Mb at 110 eV (off-resonance) and 52±13 Mb at 130 eV (on-resonance). These cross sections of Pr@C₈₂ were compared with the results of Ce@C₈₂, the only metallofullerene whose photoionization properties have ever been studied near the 4d edge of the encapsulated metal atom. The enhancement of photoabsorption due to the giant resonance was found to be similar in Pr@C₈₂ and Ce@C₈₂, but there are marked differences in the peak shapes, which can be explained as due to interference effects between the fullerene cage and the encapsulated metal atoms.     

Charge-transfer bands in crystals of alkaline earth fluorides with Eu<Superscript>3+</Superscript> and Yb<Superscript>3 + 1</Superscript>

The absorption, luminescence, and excitation spectra of CaF₂, SrF₂, and BaF₂ crystals with EuF₃ or YbF₃ impurity have been investigated in the range 1–12 eV. In all cases, strong wide absorption bands (denoted as CT₁) were observed at energies below the 4f ⁿ -4f ^{n ? 1}5d absorption threshold of impurity ions. Weaker absorption bands (denoted as CT₂) with energies 1.5–2 eV lower than those of the CT₁ bands have been found in the spectra of CaF₂ and SrF₂ crystals with EuF₃ or YbF₃ impurities. The fine structure of the luminescence spectra of CaF₂ crystals with EuF₃ impurities has been investigated under excitation in the CT bands. Under excitation in the CT₁ band, several Eu centers were observed in the following luminescence spectra: C _4v , O _h , and R aggregates. Excitation in the CT₂ bands revealed luminescence of only C _4v defects.     

Photoemission studies of single crystals of titanium carbide

The electron distribution in the valence band from single crystals of titanium carbide has been studied by photoelectron spectroscopy with photon energies h?ω = 16.8, 21.2, 40.8 and 1486.6 eV. The most conspicious feature of the electron distribution curves for TiC is a hybridization between the titanium 3d and carbon 2p states at ca. 3–4-eV binding energy, and a single carbon 2s band at ca. 10 eV. By taking into account the strong symmetry and energy dependence of the photoionization crosssections, as well as the surface sensitivity, we have identified strong emission from a carbon 2p band at ? 2.9-eV energy. Our results are compared with several recent energy band structure calculations and other experimental data. Results from pure titanium, which have been used for reference purposes, are also presented.The valence band from single crystals of titanium carbide have been studied by means of photoelectron spectroscopy, with photon energies ranging from 16.8 to 1486.6 eV.By taking into account effects such as the symmetry and energy dependence of the photoionization cross-sections and surface sensitivity, we have found the valence band of titanium carbide to consist of two peaks. The upper part of the valence band at 3–4 eV below the Fermi level consists of a hybridization between Ti 3d and C 2p states. The C 2p states observed in our spectra were mainly excited from a band about 2.9 eV below the Fermi level. The APW^5–9, MAPW¹⁰ and EPM¹¹ band structure calculations predict a flat band of p-character between the symmetry points X′₄ and K₃, most likely responsible for the majority of C 2p excitations observed. The C 2s states, on the other hand, form a single band centered around ?10.4 eV.The results obtained are consistent with several recent energy band structure calculations^{5–11, 13} that predict a combined bonding of covalent, ionic and metallic nature.     

Valence band structure of single crystal titanium carbide,studied by soft X-ray and ultraviolet photoelectron spectroscopy

Valence states of single crystal titatium carbide (TiC_x, X?0.88) have been studied with photon energies ranging from far ultraviolet (u.v.) to soft X-ray. The valence band consists of two peaks located at 3 and 10 eV below the Fermi level. This is in good agreement with recent APW band structure calculations that predict a strong hybridization of the Ti 3d and C 2p bands and a C 2s band at lower energy.     

Laser photoelectron spectrometry of Sc− and Y−: A determination of the order of electron filling in transition-metal anions

The photoelectron spectra of Sc^? and Y^? have been obtained in a crossed ion- and laser-beam experiment. Analysis of the Sc^? spectrum yields two bound terms of 3d4s² 4p configuration (¹D⁰ and ³D⁰), with EA(Sc) = 0.189 ± 0.020 eV and an excited-state binding energy of 0.042 ± 0.020 eV. Similarly, the (4d5s² 5p) ¹D⁰ ground state of Y^?is bound by 0.308±0.012eV and a (4d5s²5P)³D⁰ excited term is bound by 0.165± 0.025 eV. With the determination of the bound electronic configuration of Sc^? as 3d4s²4p, the order of filling of electron shells of the first transition series negative ions is found to be 4s²4p, 3d4s²4p, followed by 3d^k4s² (k = 3,4,…, 10).     

Luminescence and decay times of CsI:In+

Luminescence spectra of single crystals of CsI:In⁺ excited in the A(304 nm), B(288 nm), C(268 nm) and D(257 nm) absorption bands have been studied in the temperature range 4.2–300 K. Excitation in the A band at 4.2 K gives rise to the principal emission at 2.22 eV accompanied by a partly-overlapping weak band at 2.49 eV. An additional emission band at about 2.96 eV is observed on excitation in the B, C or D bands. Yet another emission band located at 2.67 eV is excited only in the D band. The relative intensities of the bands are very sensitive to excitation wavelength as well as to temperature. The origin of all these bands is assigned in terms of a model for the relaxed excited states (RES). All the luminescence spectra were resolved into an appropriate number of skew-Gaussian components. Moments analysis leads to a value of (1.35 ± 0.02) × 10¹³ rad s^-1 for the effective frequency (ω_eff) of lattice vibrations coupled to the RES. At the lowest temperature, the radiative decay times of each of the intracenter emission bands (2.22, 2.49 and 2.96 eV) show a slow decay ( ～ 10–100 μs) and a fast decay ( ～ 10–100 ns). The 2.96 eV band, which is assigned to an emission process which is the inverse of the D-band absorption, exhibits a single decay mode ( ～ 10 μs). The intrinsic radiative decay rates (k₁, k₂), the one-phonon transition rate (K) and the second-order spin-orbit splitting (D) for the RES responsible for the principal emission are: k₁ = (6.0±-0.3)×10³ s^-1, k₂ = (1.33±-0.06)×10⁵ s^-1, K = (2.4±-0.4)×10⁷ s^-1 and D = (13.8±-0.5) cm^-1.     

Atomic and electronic structures of lutetium oxide Lu2O3

The chemical composition, electronic structure, structure, and physical properties a lutetium oxide Lu₂O₃ film are studied by X-ray photoelectron spectroscopy, ellipsometry, and X-ray absorption spectroscopy. The short-range order in Lu₂O₃ is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of oxygen and the 4d _5/2 and 4f _7/2 levels of lutetium are 529.2, 5.0 and 7.4, 195.9 eV, respectively. The energy gap determined from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index is shown to increase from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu₂O₃ is 3.31.     

Enhancement of shake-up structure in alkali-metal-ion exchanged forms of α-Zr(HPO4)2 by sputtering

Mg Kα ESCA spectra of several α-Zr(PO₄)₂M₂ compounds (M = Li⁺, Na⁺, K⁺, Cs⁺) have been obtained. Satellite structure is observed at ～7–8 eV from the main P 2s peak (corresponding to ～15–16 eV from the main Zr 3d_{$\text{5}\text{2}$} peak). The intensity of the satellite depends on the counter-ion intercalated. For a given counter-ion it is strongly increased by sputtering, the rate of increase being also dependent on the counter-ion. This observation is interpreted mainly in terms of electron-defect formation similar to that involved in the formation of colour centres by radiation damage, and subsequent charge-transfer shake-up of the trapped electrons to the electron-deficient phosphorus or Zr(IV) centres.     

An AES analysis of oxide films on iron

The Auger spectra of the iron oxides have been investigated. The relative amplitudes of the Auger lines from oxygen and iron have been determined for FeO, Fe₃O₄, α-Fe₂O₃, γ-Fe₂O₃, and FeOOH. It was found that the amplitude ratio s of the O (510 eV)/Fe (703 eV) lines was, to a first approximation, directly proportional to the ratio of oxygen and iron in the chemical formula. Structure was observed in the spectra resulting from the Fe M_2,3 VV transition. Different spectra were observed for Fe, FeO, Fe₃O₄, Fe₃O₃, and FeOOH; however, the same spectra were obtained for α- and γ-Fe₂O₃.     

Gas phase high temperature photoelectron spectroscopy: an investigation of the transition metals scandium and vanadium

The He(I) photoelectron spectra of atomic scandium and vanadium have been recorded in the gas-phase. For scandium two bands associated with a (4s)^?1 ionization and one band associated with a (3d)^?1 ionization of the neutral atom have been observed. Measurement of their relative intensities allows the σ_3d:σ_4s photoionization cross-section ratio in atomic scandium to be estimated as 57.1 ± 9.0. In the atomic vanadium spectrum, six bands were seen. Four of these correspond to (3d)^?1 and (4s)^?1 ionizations of the ground state of the neutral atom, the V a⁴F state, whereas two bands correspond to (3d)^?1 ionizations of an excited state, the V a₆D state, which is approximately 2100 cm^?1 above the ground state. Measurement of the intensities of bands arising from the V a₄F state allows σ_3d:σ_4s to be estimated as 29.8 ± 2.5 for vanadium. Spectra of vanadium have been recorded with both single- and multi-detector photoelectron spectrometers. Comparison of the data acquisition rates obtained with both spectrometers demonstrates the advantage of using a multidetector instrument in high temperature photoelectron spectroscopy.