Satellite Spectra Research Articles

L2,3M2,3XAuger transitions of Ag, In, Sn, and Sb: Experiment and theory

The possibility of measuring high-resolution Auger core-level spectra produced from the ionization of deep levels has recently stimulated interest in their properties. Of special interest are those properties involving the purely atomic and the satellite spectra: the former permits evaluation of theories of atomic spectra and the latter allows study of excited states. Most such studies have treated the ${L}_{2,3}{M}_{4,5}{M}_{4,5}$ spectra of the $4d$ metals: theoretical characterization of the atomic portion of the spectra facilitated separation of the satellite spectra and study of their systematics. Reports of other such spectra in the literature are sparse. In this study we present high-resolution ${L}_{2,3}{M}_{2,3}{M}_{2,3}$ and ${L}_{2,3}{M}_{2,3}{M}_{4,5}$ Auger spectra measured for Ag, In, Sn, and Sb, and compare them with the results of nonrelativistic atomic calculations of the multiplet structure intensities using a model for closed shells with the initial state treated in the jj coupling scheme and the final state in the intermediate coupling scheme. Comparison of the theoretical results and experimental spectra shows a high degree of agreement for the ${L}_{2,3}{M}_{2,3}{M}_{4,5}$ spectra. Consideration of the ${L}_{2,3}{M}_{2,3}{M}_{2,3}$ spectra would seem to indicate the presence of many-body effects.

Solvent dependence of rotational energetics and formyl-proton long-range spin-spin coupling behavior of 2,6-dichloro- and 2,6-dinitrobenzaldehydes using dipolar couplings and temperature dependence of long-range couplings

The formyl rotational energetics, solvent effects on the energetics and formyl-proton spin-spin coupling behavior of 2,6-dichlorobenzaldehyde were studied by using dipolar couplings analysis and the temperature dependence of the spin-spin couplings. The general form of the rotational potential was taken from molecular mechanics and the conjugative sin2 Θ-type component (where Θ is the formyl-ring dihedral angle) was then optimized using the dipolar couplings obtained by analyzing 1H NMR and 13C proton satellite spectra in a liquid crystal solvent. The optimization based on the dipolar couplings gave the following rotational free energy potential: V(Θ) = 4.5 cos6 Θ + 10.7 (± 2.0) sin2 Θ, in kJ/mol. The analysis based on the temperature dependence of 6J data allowed estimation of solvent effects on the potential. For example, the potentials in acetone and in acetonitrile differ by a 1.0 sin2 2Θ (in kJ/mol). The chloroform solvent effect can be described by term of -1.0 cos6 Θ. When the formyl-proton six-bond coupling data was fit, assuming it obeyed the expression 6J(Θ) = 6J90 sin2 Θ + 6J0 and assuming 6J0 = 0.015 Hz, the analysis yielded 6J90 of -0.48 (± 0.03) Hz. The scalar coupling temperature dependence method was applied also to the conformational analysis of 2,6-dinitrobenzaldehyde.Key words: spin-spin coupling, dipolar coupling, solvent effect, rotational barrier, benzaldehyde.

Diffusion mechanism of copper (I) ion in CuAlBr4 studied by nuclear magnetic resonance

The diffusion mechanism for Cu+ was studied by means of NMR, powder X-ray diffraction and AC conductivity measurements. The satellite spectra of the 63Cu- and 27Al-NMR varied anomalously with temperature. The quadrupole coupling constant of the 63Cu nucleus and the asymmetric parameter of the 27Al nucleus changed remarkably with decreasing temperature and the quadrupole coupling constant of the 27Al nucleus did not change so much. From calculation of the electric-field-gradient tensors, it was confirmed that these temperature dependencies are produced by both Cu+ diffusion and variation of the lattice constants. The diffusion path of Cu+ in CuAlBr4 was confirmed by NMR experiments: Cu+ jumps between normal sites via an interstitial site. The ionic conductivity was evaluated by assuming that the diffusion mechanism and its value were consistent with the observed AC conductivity.

Photon energy and core hole lifetime dependences of Ag high energy Auger satellites

Understanding metallic response to the presence of a dynamic, localized perturbation, such as a finite lifetime core hole, has been the theme of many studies. Although, in XPS of such metals as Ni and Pd, shake-up satellites are common, in Auger spectroscopy, an intrinsic laboratory of many-body effects, the most extensively studied metal, Cu, manifests LVV satellites which are associated with Coster–Kronig (CK) transitions. Unambiguously identified shake-up satellites have been observed in the L 123M 45M 45 spectra of the 4d metals, studied with conventional X-ray sources and, in the L 3 threshold region, with synchrotron radiation. There remain questions concerning the origin of these satellites and their relation to the corresponding XPS spectra. Here, we report a study of the Ag L 23M 45M 45 spectra as a function of photon energy and demonstrate the evolution of the satellite spectra. The change of the satellite shapes with photon energy is directly related to the validity of the sudden approximation. Correlation of the satellite spectra with core level lifetime indicates the influence of core hole dynamics. From the experimental systematics, it becomes clear that isolation of CK effects is very difficult.

Line shape variations of Ag auger shake-up satellites outside the resonance regime

Abstract In recent publications, unambiguously identified shake-up satellites have been observed in the L123M45M45 spectra of 4d metals, studied with conventional X-ray sources and, in the L3 threshold region, with synchrotron radiation. There remain questions concerning the origin of these satellites and their relation to the corresponding X-ray photoelectron spectroscopy (XPS) spectra. We report here a study of the Ag L23M45M45 spectra as a function of photon energy and demonstrate the evolution of the line shapes of the satellite spectra. The transition from the adiabatic to sudden approximation regimes appears to occur at around 80 eV above threshold, which is much less than expected for plasmon satellites. These results may reflect the influence of quasi-atomic screening, as opposed to metallic screening. The experiments were performed using the SXS-beamline at the National Synchrotron Laboratory of Brazil (LNLS).

Hot electron effects on the satellite spectrum of laser-produced plasmas

In laser-produced plasmas, the interaction of the intense laser light with plasma electrons can produce high-energy superthermal electrons with energies in the keV range. These hot electrons can influence the level populations which determine spectral line structure. In the present paper, the effect of hot electrons on the X-ray satellite spectrum of laser-produced plasmas is studied. Calculated spectra are compared with experimental observations. Magnesium targets irradiated by three different types of laser pulses are considered. These include, a high-intensity 600 fs Nd-glass laser, a 1 ns Nd-glass laser, and a 2 ns CO 2 laser. The Nd-glass laser experiments were conducted recently at the Los Alamos Trident Facility and the CO 2 data were recorded by MISDC. High-resolution spectra were measured near the He-like resonance line of magnesium. The calculations employ an electron energy distribution which includes a thermal and a hot electron component, as part of a detailed collisional-radiative model. Plasma parameters including electron temperature, density, and hot electron fraction are estimated by choosing best fits to the experimental measurements. The calculations show that hot electrons can cause several anomalous effects. The Li-like jkl, abcd , and qr satellites can show intensities which are generally attributed to electron densities in excess of 10 23 cm -3. In addition, the relative amplitude of the intercombination line can be unusually large even at high electron densities due to enhanced collisional excitation of the 1 s2p 3 P state by hot electrons.

L23[L23]−MM[L23]andL23[M2]−MM[M2]Auger vacancy satellite spectra of argon

The deexcitation of a $1s$ core hole in argon via parallel Auger cascade branches leads to the emission of several superimposed ${L}_{23}\ensuremath{-}MM$ vacancy satellite spectra. These spectra arise from the presence of various configurations of additional ``spectator'' holes left by preceding Auger transitions. Such spectator vacancies (henceforth enclosed by brackets) cause characteristic energy shifts and a more complicated multiplet splitting. The most intense lines of the superimposed spectra have been successfully assigned previously. Here we present an extensive refinement and augmentation of that work. The experimental analysis obtained for the two particular ${L}_{23}\ensuremath{-}MM$ satellite spectra arising from the principal ${K\ensuremath{-}L}_{23}{L}_{23}$ deexcitation branch is compared to multiconfiguration Dirac-Fock calculations of energies and intensities. Excellent agreement is found, enabling an almost complete assignment of the recognizable lines. Furthermore, by comparison with the electron impact excited ${L}_{23}\ensuremath{-}MM$ spectrum a number of other lines are attributed to the normal ${L}_{23}\ensuremath{-}MM$ and the ${L}_{23}[M]\ensuremath{-}MM[M]$ satellite spectrum, which here originate, respectively, from concomitant single primary ${L}_{23}$ and ${L}_{1}$ ionization. We believe this to be the first comprehensive analysis of a compound Auger cascade spectrum.

The shapes of Auger decay lines in photoelectron satellite spectra

The theory of the shapes of Auger decay lines of satellite two-hole-one particle states accompanying photoionization based on the Green's function method is developed. The lineshapes of Auger decay of satellite states [2 s 2 p ]( 1,3 P )3 s ( 2 P ), [2 s 2 p ]( 1 P )4 s ( 2 P ) and [3 s 3 p ]( 3 P )4 s ( 2 P ) in valence p-photoelectron spectra of Ne and Ar atoms are calculated (hole states are indicated by square brackets throughout). It is shown that in some cases the Auger lineshapes reproduce the shape of the photoelectron satellite line, but in other cases Auger line may be narrower then the photoelectron line and may have opposite direction of asymmetry. The theoretical results are in agreement with experimental low-energy Auger spectra.

High Resolution X-ray Spectroscopy of Laser Generated Plasmas

The application of recently developed spectroscopic instruments in laser produced plasmas with simultaneous high spectral and spatial resolution combined with high luminosity discovered new types of x-ray spectra. These new types are characterised by the disappearance of the resonance lines and the strong emission of dielectronic satellite spectra. Several types of transitions of highly charged ions are discovered which are unknown from usual sources employed in atomic physics. New theoretical models are developed and successfully applied for the interpretation and for plasma diagnostics.

Influence of charge-exchange processes on x-ray spectra in TEXTOR tokamak plasmas: experimental and theoretical investigation

Time-resolved high-resolution soft x-ray spectra from gas-puff injected Ar impurity ions have been investigated for neutral beam heated and ohmically heated discharges in the TEXTOR tokamak. The experimental spectra show systematic deviations from corona model calculations for the line intensities of the forbidden He-like lines x, y, z and the Li- and Be-like dielectronic satellite spectra: theoretical corona model calculations predict intensities significantly too low. High-intensity Li-like inner-shell excited satellites correlate with the neutral beam injection. The discrepancies could also be observed in the stationary phase of an inductively heated discharge. In the heating phase the discrepancies are even larger. We propose charge-exchange processes between the neutral atoms and the impurity ions as an explanation of the experimental findings. Good agreement with the experimental observations can then be obtained without the need for invoking large (anomalous) diffusion coefficients. A self-consistent coupling of the population kinetics of the neutrals and the impurity ions, also taking into account charge-exchange processes from excited states of hydrogen/deuterium permit the determination of the neutral fraction and of the electron lifetime on the sole basis of impurity spectra analysis. Independent Monte Carlo simulations of neutral gas transport also provides the ionization degree in the centre and the electron lifetime. These calculations are also in good agreement with the spectroscopic results.

Imaging x-ray crystal spectrometers for the National Spherical Torus Experiment

A new type of high-resolution x-ray imaging crystal spectrometers is described for implementation on the National Spherical Torus Experiment (NSTX) to provide spatially and temporally resolved data on the ion temperature, toroidal and poloidal plasma rotation, electron temperature, impurity ion-charge state distributions, and impurity transport. These data are derived from observations of the satellite spectra of heliumlike argon, Ar XVII, which is the dominant charge state for electron temperatures in the range from 0.4 to 3.0 keV and which is accessible to NSTX. Experiments at the Torus Experiment for Technology Oriented Research (TEXTOR) demonstrate that a throughput of 2×105 photons/s (corresponding to the count-rate limit of the present detectors) can easily be obtained with small, nonperturbing argon gas puffs of less than 1×10−3 Torr l/s, so that it is possible to record spectra with a small statistical error and a good time resolution (typically 50 and 1 ms in some cases). Employing a novel design, which is based on the imaging properties of spherically bent crystals, the spectrometers will provide spectrally and spatially resolved images of the plasma for all experimental conditions, which include ohmically heated discharges as well as plasmas with rf and neutral-beam heating. The conceptual design, experimental results on the focusing properties, and relevant spectral data from TEXTOR are presented.

Theoretical Analysis of Stabilization Processes of Ar Hollow Atoms Formed in a Solid with the MSCL Model

Using the multistep-capture-and-loss (MSCL) model a theoretical analysis for the K satellite spectra emitted from Ar hollow atoms formed in a solid observed by Briand et al is carried out. It is found from the simulation of the spectra with the model that the feature of the spectra is strongly dependent on the magnitude of the rate of electron capture from a solid by a projectile ion.

-V spectrum of silicon and related energy level diagram

The satellite spectrum of silicon is reported. It is found to consist of three lines at 1891.4, 1896.7 and 1903.0 eV. These have been assigned to the - group of transitions. The transition array has been, for the first time, analysed in terms of ten components as against the four reported in the literature. The relative contribution of each of the ten components in emitting these lines has been estimated and hence these lines have been identified as , and satellites, respectively. A weak structure at 1885.0 eV, in addition to the - spectrum, has also been observed and has been tentatively assigned to a - hypersatellite transition. The energy level diagram for the , and levels has also been presented.

From a Single 1s Hole to a Multiply Charged Ion: the Cascade L23–MM Spectrum of Argon

The L23–MM spectrum of argon emitted after 1s photoionization represents a superposition of several vacancy satellite spectra. They are separated by means of electron-ion coincidence spectroscopy. Excellent agreement of the gross spectral structure is found with a calculation in relativistic single configuration average approximation. With the aid of data from the literature we identify sequentially emitted L23[L23]–MM[L23] and L23[M2]–MM[M2] lines and locate intermediate 2p53p4 levels. Elaborate multiconfiguration Dirac-Fock calculations of transition energies and intensities have been performed for these two spectra. Their results show very good agreement with observation, thereby confirming and extending the experimental analysis. Other lines are shown to be known from the well investigated L23–MM and L23[M]–MM[M] spectra. Virtually all recognizable lines of the densely packed cascade spectrum are assigned.

Multistep-capture-and-loss model for stabilization processes of hollow Ar atoms formed in a solid

Using the multistep-capture-and-loss model, we carry out a theoretical analysis for the K satellite spectra emitted from Ar hollow atoms formed below the surface of a solid target, as observed by Briand et al. [Phys. Rev. A 54, 4136 (1996)]. It is found that the feature of the K x-ray spectra is mainly governed by the magnitude of the rate for the electron capture from a solid target by a highly charged ion.

Kinetics of phase transitions in modulated ferroelectrics: Time-resolved neutron diffraction from Rb2ZnCl4

The kinetics of the ferroelectric phase transition between modulated phases in Rb2ZnCl4 at about 190K has been investigated by time-resolved neutron scattering. Observing the time dependence of satellite spectra, it is found that the structural changes associated with the field-induced transformation proceed on a millisecond time scale. Under the influence of fast cycling strong electric fields unusual non-equilibrium states are obtained which are modulated in space as well as in time and characterised by the presence of internal mechanical strains.

Valence satellite and 3p photoelectron spectra of atomic Fe and Cu

The 3p photoelectron spectra of atomic Fe and Cu, and the Fe outer-shell satellites have been investigated. The complex multiline structure of the Fe spectra has been resolved using high-resolution electron spectroscopy. The thresholds of the direct 3p photoionization have been determined and are compared with experimental results from photoabsorption measurements and Auger spectra, and with the multiplet structures calculated taking into account intershell and configuration interaction. The stepwise decay of highly excited Fe states into has been verified by the detection of satellite lines with binding energies above the lowest ionization threshold.

Threshold phenomena in high-resolution core-level photoelectron spectroscopy: the ethene molecule

Abstract The creation of a core hole in a molecule leads to vibrationally and electronically excited states of the resulting ion as the system adjusts to the new molecular potential. These can be observed in the corresponding photoelectron spectrum as vibrational fine structure on the main line and as satellite excitations, respectively. In the region near the photoelectron threshold, however, other phenomena occur, such as shape resonances, multi-electron excitations and conjugate satellite processes, which affect the partial cross-sections of the various channels. As an example, we present C 1s photoelectron spectra of ethene (C 2 H 4 ) measured with high energy resolution in the near-threshold region. The vibrational fine structure on the C 1s −1 line can be fitted with two progressions with energies of 185(±5) meV and 424(±10) meV, which can be assigned to totally symmetric modes. It is expected that vibronic coupling occurs, as in the case of the corresponding photoabsorption spectrum, and that an antisymmetric stretching mode contributes to the higher energy progression. This cannot be determined from the fit, however. There is no definitive evidence for a shape resonance in the C 1s single-hole cross-section. In addition, the C 1s shake-up satellite spectrum was also measured with high resolution in the near-threshold region. Apart from the well-resolved π–π* satellites, S 0 and S 1 , the measurements revealed several other peaks. Their partial cross-sections and asymmetry parameters indicate the existence of conjugate processes.

Investigation of the Ar L23-MM Auger spectrum, emitted after 1s ionization, by means of e–ion and e–e coincidences

Abstract The L 2 3 –MM Auger spectrum of argon observed after 1s ionization is a superposition of several complete L 2 3 –MM spectra which are emitted in the presence of additional vacancies being left by preceding transitions and acting as `spectators'. The spectrum is decomposed into these partial vacancy satellite spectra by measuring in coincidence the electron energy and the charge of the final ion. Moreover the sequential emission of certain partial spectra is demonstrated via electron–electron coincidence spectroscopy. The results of both the e–ion and the e–e coincidence experiment are in very good agreement with those of a published step-by-step calculation of the deexcitation cascade in single configuration average approximation. With the help of the known levels from the 2p 4 and 3p 2 configurations pairwise sequential individual 2p 4 →2p 5 3p 4 →2p 6 3p 2 transitions have been identified. The pertinent partial spectra are compared to relativistic calculations of transition energies and rates. Very good agreement is found, permitting the identification of the spectroscopically inferred intermediate 2p 5 3p 4 levels.

Evolution of the CuKα3,4satellites from threshold to saturation

Photoexcited Cu $K{\ensuremath{\alpha}}_{3,4}$ satellite spectra were measured as a function of excitation energy, from threshold at $\ensuremath{\sim}$10.010 keV to saturation at $\ensuremath{\sim}$11 keV. A two-regime behavior is found, where in the near-threshold regime (TR) both the shape and the intensity of the spectrum vary. In the higher-energy regime (GR) only the intensity varies but not the shape. The GR spectra are well described by relativistic Dirac-Fock calculations. The analytic Thomas model, applicable in this adiabatic regime, does not agree well with the measured intensity variation with excitation energy. The continuous intensity rise from zero at threshold confirms the shake theory prediction of a pure shake-off process for inner-shell, medium-$Z$ atom satellites. The thresholds for the individual spectral features, the overall shape variation, and the variations of the individual lines in the TR regime are determined, and discussed.