Paramagnetism and shake-up satellites in X-ray photoelectron spectra

The correlation between paramagnetism and the shake-up satellites in the X-ray photoelectron spectra of the 3d transitional-metal compounds is examined and explained in terms of modified selection rules governing the shake-up transitions.     

Shake-up satellites in x-ray photoelectron (ESCA) spectra of 5f0 Th(IV) compounds

X-ray photoelectron (ESCA) spectra of the Th 4f levels have been recorded in 12 Th compounds. Weak satellites are observed in all the 4f spectra at binding energies 4–6 eV from the primary photolines. On the basis of a multiple scattering calculation in ThO₂, these satellites are assigned to ligand (e.g. O 2p) to Th 5f shake-up transitions. As with La 3d satellites, the satellite intensities correlate well with the nephelauxetic order of ligands.     

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.     

Shake-up satellites in Hel photoelectron spectra: N2O4 and CH3O

Low-lying vacant molecular orbitals may lead not only to a breakdown of Koopmans' theorem but also to satellite structure in photoelectron spectra. This paper reports examples of the relatively infrequent appearance of shake-up satellites in Hel photoelectron spectra, namely those of N₂O₄ and CH₃NO. An extended version of the HAM/3 program was used to interpret these spectra.     

Sulphur Kβ X-ray emission spectra of SO2−3 and SO3F− ions

The SK_β X-ray emission spectra of the SO^2?₃ and SO₃F^? ions are studied in detail and the observed fine structures are interpreted with the aid of existing molecular orbital (MO) calculations. The different MO methods are compared with regard to success and the effect of d-orbitals is discussed. The spectrometer is a double-crystal type with an instrument fwhm resolution of 0.25 eV for SK_β X-rays.     

Satellite Phenomena in X-ray photoelectron spectra of actinide compounds

Satellite structure to one side of the 4f photoelectron lines of a number of thorium compounds has been investigated. The origin of these and similar lines observed in uranium compounds is discussed together with those recorded near the 3d photoelectron signals of lanthanide compounds.     

Phonon assisted site-to-site electronic energy transfer between Eu3+ ions in an amorphous solid

We have investigated the dynamics of phonon assisted electronic energy transfer between Eu³⁺ ions, experiencing different crystal fields in an amorphous Ca(PO₃)₂ matrix, using the technique of time-resolved fluorescence line-narrowing (TRFLN). From the concentration and temporal dependence of the transfer rate, the mechanism of the ion—ion electronic coupling has been identified as electric dipole—dipole. Both the excitation wavelength independence and the power law temperature dependence of the transfer rate identify the mechanism of the phonon participation in the transfer process as one involving a two-phonon process, with one-phonon action at each of two coupled ion sites.     

2s and 2p X-ray photoelectron spectra of Ti4+ ion in TiO2

A detailed experimental study of the 2s- and 2p XPS spectra of TiO₂ revealed new (charge-transfer) shake-up satellite structures (at 4.0–5.0 eV from the main peaks) which can be explained using molecular orbital representation. The satellite peaks, situated at about 26 eV from the main peaks, the origin of which was in doubt in the previously reported works are shown conclusively in the present investigation to be energy loss peaks. The relative energies and intensities of the observed satellites are presented and the theoretical implications of the work are discussed.     

Low energy satellites in X-ray emission and X-ray photoelectron spectra of some transition metal ions: The identification of multiplet splitting effects

X-ray emission and X-ray photoelectron spectra from manganese and nickel compounds are compared. It is suggested that a comparison of the satellite structure of Kβ_1,3 X-ray peaks and photoelectron 3p peaks can be used to determine their origin since identical features would only be expected to arise from multiplet effects. Shake-up, shake-off and other multi-electron effects should therefore give rise to low (kinetic) energy satellites unique to the photoelectron spectrum.     

Preionization effects in photoelectron spectra: vibrational enhancement of NO+, X1Σ+

The nature of the superexcited state(s) responsible for part of the vibrational intensity distribution of the NO⁺, X¹Σ⁺, photoelectron band produced by 104.8–106.7 nm irradiation is discussed.Franck-Condon factors for preionization are calculated and a comparison with experiment is attempted with the result that preionization appears as the dominant process at these wavelengths.     

Energy transfer between Eu2+ ions in RbMgF3 crystals

Time-resolved spectroscopy after pulsed nitrogen laser excitation was used to characterize the energy transfer between Eu²⁺ ions in different crystal field sites in RbMgF₃ crystals. The results are consistent with electric dipole—dipole interaction and indicate that the Eu²⁺ ions are forming clusters in this host. As temperature is raised, the upper crystal field components of the metastable states of the ions become thermally populated and this changes the characteristics of the transfer process.     

Optical oscillator strengths of 3p63d 2D → 3p53d22po, 2Do, 2Fo transitions in Co8+, Cu1O+ and Zn11+ ions

We have calculated the excitation thresholds and optical oscillator strengths (OOS) for 3p⁶3d ²D → 3p⁵3d²²po, ²Do and ²F^o transitions Co⁺⁸, Cu¹⁰⁺ and Zn¹¹⁺ ions of the potassium isoelectronic sequence using Hartree-Fock (HF) and configuration interaction (Cl) wavefunctions for both initial and final states. Our Cl values of the length and velocity form of OOS are in good agreement with each other. The trends in the oscillator strengths for the potassium isoelectronic sequence are plotted.     

Satellite phenomena in the X-ray photoelectron spectra of some titanium compounds

The extra peak, located at ca 13.6 eV on the high-binding-energy side of the core levels of titanium in rutile, anatase and barium titanate, probably arises from a shake-up process involving an O(2p) → Ti(4s) transition.     

H+ and OH− ions in aqueous solutions vibrational spectra of hydrates

The ions (H₂O ... H ... OH₂)⁺ and (HO ... H ... OH)^? are the simplest stable H⁺ and OH^? hydrates in aqueous acid and base solutions, respectively. Using the attenuated total reflection method, the IR spectra of aqueous HCl and KOH solutions are obtained and the assignment of the H₅O₂⁺ and H₃O₂^? vibrational frequencies is performed. The absorption spectrum of the OHO fragment is separated from the spectra of the solutions investigated. This spectrum exhibits a broad continuous band and two rather narrow bands at its background which are assigned to the antisymmetrical stretching vibration and to the bending vibrations of the fragment. A theoretical model is suggested which explains the origin of the continuum by a strong proton-phonon coupling. The model takes into account the large number of low-frequency vibrational modes of the system; the frequency dispersion for these modes is assumed to be sufficiently large. The continuous absorption bandshape is calculated in the Condon approximation. The theoretical absorption curve is in good agreement with experiment at reasonable values of the parameters involved.     

X-ray photoelectron spectra and structure of cobalt compounds with N-heterocyclic ligands

The electronic structure of cobalt complexes with bi-, tri-, and tetradentate ligands and the mutual influence of ligands in them have been studied by X-ray photoelectron spectroscopy. The Co2p, N1s, and O1s photoelectron spectra have been studied. Unlike low-spin Co(III) complexes, the high-spin Co(II) compound exhibits a strong satellite line in the Co2p spectrum. For the high-spin Co(II) compound having unpaired 3d electrons, the Co2p _1/2-Co2p _3/2 spin-orbit splitting is larger than that in the low-spin Co(III) complexes. All cobalt complexes under consideration contain strongly bound dioxygen, which can be considered an inherent structural unit.     

Nature of satellites in x-ray photoelectron spectra XPS of paramagnetic cobalt (II) compounds

XPS spectra of a number of paramagnetic Co(II) compounds are studied and the correlation between the intensity of the Co 2_{p$\text{3}\text{2}$} satellite and the magnitude of its magnetic moment is shown. A new approach is put forward to explain the experimental data.     

Fe3s X-ray photoelectron spectra of polynuclear iron complexes

Specific features of the electronic structure and spin magnetic state of iron atoms in bi-, tri-, and hexanuclear iron trimethylacetate complexes were studied by X-ray photoelectron spectroscopy. A correlation was found between the ionicity (of the spin state of iron atoms) and Fe3s binding energies, exchange splitting of the final photoionization state, and the energy position and intensity of charge-transfer satellites. Nonequivalent iron states were identified in tri- and hexanuclear complexes. The overall magnetic moment of the complexes was found to decrease with an increase of the individual magnetic moments of iron atoms, which is evidence of complicated mutual orientation of atomic magnetic moments in the complexes.     

13C NMR spectra of η3 -allylmanganesetetracarbonyl compounds; structural implications

The ¹³C NMR spectra of η³-allylmanganese tetracarbonyl complexes are consistent with an overall C_s, symmetry and involving a σ_v plane in the Mn(CO)₄ fragment. A dynamic carbonyl interchange process was looked for but the results are inconclusive, however the barrier for this process is certainly greater than 42 kJ/mol. This observation suggests an octahedral type geometry rather than a square pyramid type configuration.     

Radiative lifetimes of the CO a′3Σ+, b3Σ+, c3Π, d3Δ and B1Σ+ states. Absolute emission cross sections for t

Radiative lifetimes have been measured for the CO a′³Σ⁺(ν′=4–9), b³Σ⁺(ν′= 0), c³Π(ν′=0), d³Δ(ν′=1–16) and B¹Σ⁺(ν′= 0) states. Our experimental values, arranged in the same order, are 7–10 μs, 56 ns, 16 ns, 3–7.5 μs, 34 ns. Some of these values disagree with the results of previous experiments. To our opinion this is due to an incomplete identification of the emission spectrum in regions where many bands may overlap, dependent on the applied spectral resolution. For the a′Σ⁺?a³Π and d³Δ?a³Π emissions effective cross sections for quenching by CO molecules are given. In connection with the identification of the spectrum, absolute emission cross sections for electrons incident on CO have been measured for the b³Σ⁺?a³Π and c³Π?a₃Π transitions. For an electron energy, corresponding to the maximum of the excitation function we find cross sections of 5.94 (?1.2) × 10^?18 cm² and 0.630 (? 0.13) × 10^?18 cm², respectively.