Photoelectron Spectra Of CO Research Articles

The structural, magnetic and electrical properties of cobalt-doped SrRuO3

The influence of Co doing at Ru site on the structural, magnetic and electrical properties of polycrystalline SrRu1-xCoxO3 (0≤x≤0.3) have been investigated. All the compounds have single phase with Pnma space group. The chemical homogeneity of synthesized samples are confirmed by scanning electron microscopy and energy-dispersive spectroscopy. The X-ray photoelectron spectra of Co and Ru reveal that both two transition metal elements exist in the mixed ionic pair, that is Co3+/ Co2+ and Ru5+/ Ru4+. With Co doping, the ferromagnetic transition temperatures Tc decreases moderately, but the magnetic moment drops substantially. The coercive field Hc is enhanced by the substitution of Co, which may originates from the high degree randomness of Co and Ru ions, as well as from the improved competition between ferromagnetic Ru4+-O-Ru4+ and antiferromagnetic Co2+-O-Ru5+ and/or Co3+-O-Co3+ iterations. Co substitution in SrRu1-xCoxO3 system weakens the itinerant properties of Ru 4d electrons and results in localization of mobile electrons, and thus gives rise to the metal-insulator transition at around x = 0.15.

A HIGH-RESOLUTION VACUUM ULTRAVIOLET LASER PHOTOIONIZATION AND PHOTOELECTRON STUDY OF THE CO ATOM

ABSTRACT We have measured the vacuum ultraviolet–photoionization efficiency (VUV–PIE) spectrum of Co in the energy range of 63,500–67,000 cm−1, which covers the photoionization transitions of Co(3d74s2 4F9/2) Co+(3d8 3F4), Co(3d74s2 4F7/2) Co+(3d8 3F3), Co(3d74s2 4F9/2) Co+(3d8 3F3), Co(3d74s2 4F9/2) Co+(3d8 3F2), and Co(3d74s2 4F9/2) Co+(3d74s1 5F5). We have also recorded the pulsed field ionization photoelectron spectrum of Co in the same energy range, allowing accurate determinations of ionization energies (IEs) for the photoionization transitions from the Co(3d74s2 4F9/2) ground neutral state to the Co+(3F J ) (J = 4 and 3) and Co+(5F5) ionic states, as well as from the Co(3d74s2 4F7/2) excited neural state to the Co+(3d8 3F3) ionic state. The high-resolution nature of the VUV laser used has allowed the observation of many well-resolved autoionizing resonances in the VUV–PIE spectrum, among which an autoionizing Rydberg series, 3d74s1(5F5)np (n = 19–38), converging to the Co+(3d74s1 5F5) ionic state from the Co(3d74s2 4F9/2) ground neutral state is identified. The fact that no discernible step-like structures are present at these ionization thresholds in the VUV–PIE spectrum indicates that direct photoionization of Co is minor compared to autoionization in this energy range. The IE values, the autoionizing Rydberg series, and the photoionization cross sections obtained in this experiment are valuable for understanding the VUV opacity and abundance measurement of the Co atom in stars and solar atmospheres, as well as for benchmarking the theoretical results calculated in the Opacity Project and the IRON Project, and thus are of relevance to astrophysics.

Spectral distributions of vibrational excitations accompanying 1s shell photoionization in small molecules

Distribution of vibrational excitations accompanying inner-shell ionization in small molecules is investigated. Within the vibrationally dependent-fixed-nuclei and the harmonic oscillator models the distribution is presented as a product of the Franck–Condon distribution and the interferential factor. It is shown that this factor varies strongly in the shape resonance vicinity and oscillates far above the core-ionization threshold. Analytical relationships between the spectral distributions and the potential functions of initial and final molecular states as well as intramolecular interference of scattered photoelectron waves are obtained and applied for the description of C 1s ionization in CO. The extended oscillations of the intensity ratio of vibrational components v′ = 0 and v′ = 1 of C 1s photoelectron spectrum of CO far above the threshold are discussed in more detail. The non-Franck–Condon, chemical and multi-electron effects on the distributions are also examined.

A ZEKE photoelectron study of the D [formula omitted] and 3 [formula omitted] satellite states of CO +

The zero kinetic energy (ZEKE) photoelectron spectrum of CO has been obtained from 22.3–23.75 eV with resolution of 0.7 meV and shows the structure of the D 2 Π ( v +=0–8) and 3 2 Σ + ( v +=0–4) bands. The intensity with which these are formed at threshold, band origins, rotational constants and spin orbit splittings of the D 2 Π state are reported. The decreased lifetimes of the D 2 Π , v +=3, 4 levels are also recorded. All states observed are above the lowest dissociation limit of the ion, and these spectra provide information about the intramolecular dynamics in this high energy region.

Autoionisation of doubly excited states in the C 1s photoexcitation of CO

The vibrationally resolved C 1s −1 main line in the photoelectron spectrum of CO has been investigated just above the C 1s ionisation threshold where the absorption cross section is characterized by sharp, intense doubly excited states. They decay in part via resonant Auger processes, but can also couple via autoionisation to the C 1s −1 continuum, causing striking changes in the vibrational fine structure. In some cases very high vibrational levels up to quantum numbers of ν′= 7 are populated.

Relaxation effects in C1s photoionisation of CO: a high resolution photoelectron study in the near-threshold region

The angle-resolved C1s photoelectron spectrum of CO has been measured with high resolution in the threshold region. An analysis of the vibrational fine structure on the main C1s photoelectron line indicates that the vibrational energy of the CO + ion is 302 ± 2 meV and the lifetime broadening is 78 ± 10 meV. The form of the vibrational fine structure changes dramatically with photon energy due to the influence of the σ ∗ shape resonance and the double excitations. On a more quantitative level, this is reflected in the corresponding partial cross-sections and asymmetry parameters. A meaningful comparison of these data with theory awaits, however, the inclusion of dynamic effects in the calculations. In addition to the direct shake-up satellites observed at high photon energies several additional, conjugate shake-up satellites are found in the near-threshold region. The lowest of these overlap partly with the triplet-coupled, direct shake-up satellite S 1 but it is still possible to determine the cross-section of the latter to within a few electronvolts of threshold.

The vibrationally resolved participator Auger spectra of selectively excited C 1s(2σ)−12π1 vibrational states in carbon monoxide

The fully vibrationally resolved participator Auger spectra originating from the decay of the C 1s(2σ)−12π1 resonance in CO are presented. The C 1s(2σ)−12π1 v′=0 resonance has been excited with a 75 meV monochromator bandpass, i.e., in Auger resonant Raman conditions, and the participator Auger spectrum observed. The C 1s(2σ)−12π1 v′=1 resonance is also excited and the corresponding participator Auger spectrum observed with a monochromator bandpass slightly larger than the inherent width. The results are compared to theoretical simulations using coherent lifetime-vibrational interference theory which accounts for the details of the spectrum. We have observed an interference shift on the transitions to different vibrational sublevels in the final state. A high resolution C 1s photoelectron spectrum of CO is also presented. The lifetime width of the C 1s core–hole state is determined to be 97(10) meV, whereas the C 1s(2σ)−12π1 resonance is measured to have a width of 86(10) meV.

Spin-polarized electronic structure of cobalt cluster anions studied by photoelectron spectroscopy

The photoelectron spectra of Co−n (3≤n≤70) were measured at the photon energy of 4.025 eV by use of a XeCl excimer laser. For Co−n with n=3, 4, and 6, the geometric and electronic structures were obtained from the spectra in comparison with the calculated spectra by the spin-polarized DV-Xα method. The spectra observed are reproduced reasonably well by the calculation with postulating the most probable geometrical structures. It is revealed that the 3d band with the majority spin is separated by 1.0–2.8 eV from that with the minority spin; the former is completely filled while the latter is partly filled and extends above Fermi level. The magnetic moments and the average exchange energies of these cluster anions were estimated. For Co−n with n≥7, the observed electron affinity depends linearly on the reciprocal of the cluster radius and approach the work function of a cobalt metal, as n increases. Below n=6, the electron affinity deviates from the linear dependence. This finding indicates that a size-dependent transition in the electronic structure occurs at n≂7. The spherical conducting drop model suggests the presence of mobile electrons in Co−n with n≥7.

Photon Energy Dependence of the Vibrational Fine Structure in Core Level Photoemission Spectra Near Threshold

AbstractThe C 1s and N 1s main lines in the photoelectron spectra of CO, CO2, CH4, C2H2, C2H4, C2H6, N2, and N2O have been measured with high resolution in the threshold region, revealing in each case the extent of the rich vibrational fine structure. Using a simple line shape analysis which allows for the effect of post‐collision interaction, the vibrational energies and approximate lifetimes of the core‐excited ions are determined. The relative intensities of the vibrational lines change dramatically with photon energy due to the influence of shape resonances and double excitations.

Electron affinity of dicarbonylnitrosylcobalt (Co(CO)2NO) measured by negative-ion photoelectron spectroscopy

In this work, we present the fixed-frequency (at 355 nm) negative-ion photoelectron spectrum of Co(CO) 2 NO - . Analysis of the spectrum yields the electron affinity of Co(CO) 2 NO; EA[Co(CO) 2 NO]=1.73±0.03 eV. The lack of extensive vibrational progressions in the spectrum is consistent with the neutral species and the negative-ion having similar equilibrium geometries

Photon energy dependence of the high resolution C 1s photoelectron spectrum of CO in the threshold region.

The C 1s photoelectron spectrum of CO has been measured with high resolution in the threshold region. The data exhibit hitherto unresolved vibrational structure on the C 1s main photoelectron line as well as new features in the satellite region. The vibrational energy of the ${\mathrm{CO}}^{+}$ ion is 301\ifmmode\pm\else\textpm\fi{}3 meV. The vibrational structure changes dramatically with photon energy due to the influence of the ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$ shape resonance. The new satellite lines which are not present at high photon energies are attributed to conjugate shakeup processes.

Satellite intensities in the K-shell photoionization of CO.

A recently proposed scheme for calculating K-shell ionization cross sections in atoms and molecules using the relaxed-core Hartree-Fock (RCHF) approximation is extended to the treatment of shakeup processes. As an example, this scheme is applied to the \ensuremath{\pi}-${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ satellites in the C 1s photoelectron spectrum of CO. These results for the (S0, S1) pair of \ensuremath{\pi}-${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ satellite states reveal strong interference effects between the ``direct'' (bound-free dipole integral) and ``conjugate'' (bound-free overlap integral) contributions in the transition moment at near-threshold energies. These effects are particularly dominant in the k\ensuremath{\pi} subchannel and, for the triplet-coupled satellite (S1), lead to a drastically increasing cross section with decreasing photon energy. For the singlet-coupled satellite (S0) destructive interference leads to a comparatively small cross section near threshold. While these findings may explain the strikingly different behavior of the S0 and S1 satellite intensities in recent experiments, the present results also show distinct \ensuremath{\sigma}-type shape resonances in both satellite channels at about 10 eV photoelectron energy that are apparently at variance with the experimental evidence. An analysis of the RCHF transition moment via perturbation theory shows that already in first order some potentially important dynmical contributions are missing. In these studies a direct method based on the Schwinger variational principle and single-center expansion techniques is used to obtain the photoelectron orbitals.

Multielectron excitations in high-energy photoelectron spectra of CO adsorbed on Ni(100).

High-resolution x-ray-excited core-level shake-up and valence-electron spectra of CO adsorbed on Ni(100) in the c(2\ifmmode\times\else\texttimes\fi{}2) structure are presented. A number of newly resolved structures are reported. The C 1s and O 1s shake-up spectra show pronounced differences. The shake-up transitions are treated as local molecular excitations in the presence of the core hole. It is proposed that transitions from the 2${\ensuremath{\pi}}^{\mathrm{*}}$ screening orbital into 3p and other higher states with Rydberg character give rise to the most intense shake-up peaks in adsorbed CO. In the C 1s spectrum a low-energy satellite is identified as an excitation from bonding to antibonding 2${\ensuremath{\pi}}^{\mathrm{*}}$-3d combinations. The high-energy shake-off continua reveal several broad structures which are interpreted as autoionizing or shape resonances in the shake-off continua. These features are compared with thresholds observed in photon-stimulated-ion-desorption spectra for adsorbed CO. The difference spectrum between the valence region of Ni with and without adsorbed CO reveals several features over an energy range of 40 eV. The 3\ensuremath{\sigma} state and the correlation satellites are compared with features in the autoionizing spectra at the core-level thresholds.

ChemInform Abstract: X‐Ray Photoelectron Spectroscopy Studies of Some Cobalt(II) Nitrate Complexes

X-ray photoelectron spectra of Co(NO3)2·2L with L = tdpo, tppo and tpyrp, were recorded and interpreted. It seems that in these complexes tpyrp is the strongest electron donor, followed by tdpo and then tppo. In these complexes a stronger electron donor ligand results in a more ionic Conitrate bond, and it could thus result in a less stable complex. Paramagnetic CoII satellite structures were observed. The modified Auger parameters (α′) were calculated and used to compare the polarizability of the compounds to each other. Co(NO3)2·2tpyrp seems to be the most polarizable of the three complexes, and Co(NO3)2·2tppo the least polarizable.

X-ray photoelectron spectroscopy studies of some cobalt(II) nitrate complexes

X-ray photoelectron spectra of Co(NO 3) 2·2L with L = tdpo, tppo and tpyrp, were recorded and interpreted. It seems that in these complexes tpyrp is the strongest electron donor, followed by tdpo and then tppo. In these complexes a stronger electron donor ligand results in a more ionic Conitrate bond, and it could thus result in a less stable complex. Paramagnetic Co II satellite structures were observed. The modified Auger parameters (α′) were calculated and used to compare the polarizability of the compounds to each other. Co(NO 3) 2·2tpyrp seems to be the most polarizable of the three complexes, and Co(NO 3) 2·2tppo the least polarizable.

High resolution angle resolved photoelectron spectrum of co excited with polarized resonance radiation

The photoelectron spectrum of CO involving ionization from the three outermost valence orbitals has been studied by He I, He II, Ne I and Ne II excitation. Angular distributions of the electrons have been obtained and β-parameter spectra (βPS) showing the value of β recorded in small energy steps at high resolution are presented. The vibrational structure of the ionic states has been resolved in detail. In the spectrum excited by He Iα radiation, long progressions have been observed, the one of the X state extending up to υ' = 33. By using the energies of this progression, the coefficient of the third order term ħω ey e(υ+1/2) 3 in the power series in υ+1/2 for the vibrational energy has been determined. The value is ħω ey e = −(12±3) × 10 −3cm −1. The intensity distribution in the vibrational progressions of both the Ne I and He I excited spectra indicates that the ionization proceeds partly via autoionization from a vibrationally excited level. For these excitation sources, large variations in the β -value have also been observed. They are associated with both autoionization and shape resonances. At the higher excitation energies of Ne II and He II, no such variations are present. A similar study of N 2 gave no indications of autoionization contributions to the He I excited spectrum.

High resolution UV photoelectron spectroscopy of CO +2, COS + and CS +2 using supersonic molecular beams

Very high resolution HeI (584 Å) photoelectron spectra of CO + 2, COS +, and CS + 2 are presented. The spectra were obtained by using supersonic molecular beams to eliminate the rotational and Doppler broadenings. The spin-orbit split components in the Π bands are all explicitly resolved. The removal of the inelastic scattering peaks, due to the use of molecular beams, allowed new features to be observed in the B̃ and C̃ bands of CS + 2, and new spectroscopic constants were derived.

Near-threshold measurements of the C 1s satellites in the photoelectron spectrum of CO.

The cross sections and asymmetry parameters of the two $\ensuremath{\pi}\ensuremath{-}{\ensuremath{\pi}}^{*}^{2}\ensuremath{\Sigma}^{+}$ shakeup satellites on $\mathrm{C} 1s$ in the photoelectron spectrum of CO are found to differ significantly in the threshold region. The first satellite (due to triplet $\ensuremath{\pi}\ensuremath{-}{\ensuremath{\pi}}^{*}$ coupling) shows intensity enhancement near threshold whereas the second satellite (singlet $\ensuremath{\pi}\ensuremath{-}{\ensuremath{\pi}}^{*}$ coupling) decreases in intensity as expected for the adiabatic limit. Moreover, the data indicate that a shape resonance in the first-satellite channel is responsible for the observed effect rather than a conjugate shakeup process.

High resolution angle-resolved photoelectron spectrum of CO 2, excited with polarized resonance radiation

The He(I) excited and angle-resolved photoelectron spectrum of CO 2 is investigated using a focussing VUV-polarizer. High resolution combined with the additional information given by comparing spectra taken at different angles permits detailed analysis of the vibrational structure. β-values are given for all vibrational components hitherto observed in the photoelectron spectrum of the ≈X, ≈A, ≈B and ≈C electronic bands. Single excitations of the v 3 mode with vibrational energies 181 meV in the estate and 279 meV in the ≈B-state are reported. The peak at 360 meV vibrational energy in the ( ≈C-state is reinterpreted as a single v 3 excitation. The β-values of the most intense peaks are also measured using Ne(I) (16.67 and 16.85 eV), Ne(II) (26.86 and 26.95 eV) and He(II) (40.81) resonance radiations.

High-resolution UV photoelectron spectrum of CO 2

The highly-resolved HeI photoelectron spectrum of CO 2 is presented and its vibrational structure studied in detail. In the X̃ 2Π g ionic state the v 3 antisymmetric mode is found to be excited in double quanta ( v 1- v 2- v 3 = 0. 0. 2) with energy hv 3 = 181 meV. In the C̃ 2Σ g + state a single quantum of the same mode is found to be excited ( hv 3 = 189 meV) in combination with a v 1 excitation. Vibronic interaction with vibrational levels in the B̄ 2Σ u + state of the ion is suggested to promote this (1, 0, 1) excitation. It is established that inelastic scattering processes contribute to the vibrational structure in the C̃ 2Σ g + band. The spin-orbit splitting in the X̃ 2Π g is determined to be 19±1 meV and 10±2 eV in the Ā 2Π u state. Vibronic structure is resolved in the X̃ 2Π g band where the Renner-Teller coupling constant is determined to be ϵ = 0.21±0.02 and the vibrational energy of the v 2 mode as 60±7 meV. In the Ā 2Π u state the v 2 energy is found to be hv 2 = 60 meV from the observed hot-band structure.