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[en] Variation trends across the AnO2 series of An5f-electron covalent bonding and An5f→O3s, O2p→An5f charge transfer energies, are studied using DV-Xα relativistic spin-polarised computation of electronic structures applied to 11 'AnO8' clusters, from ThO8 to FmO8. It is found that the binding energies of 5f orbitals, therefore the An5f-O2p hybridisation, are increasing though the 5f orbitals are localising across the An series. In our calculations, the 3s and 3p ionic-like orbitals of O2- ions are included for the first time as LCAO-MO bases. Then, the conduction band is a mixing of O3s and An6d and its lower edge corresponds to an O3s-dominated state. Moreover, the calculated charge transfer (CT) energies of An5f→O3s and O2p→An5f transitions show the so-called tetrad effect when CT energies, respectively increasing and decreasing across the AnO2 series. It is pointed out that the tetrad effect here comes mainly from the special spin-polarised pattern of 5f levels and the increasing general trend of 5f binding energies. (orig.)
[en] A background correction method based on wavelet transform was devised and applied to inductively coupled plasma atomic emission spectrometry (ICP-AES). The proposed approach separated background from analyte signal according to their different frequencies. Compared with the analyte signal, the background has a low frequency. By removal of the components attributed to the signal, the background over the spectral window of the analyte line can be fitted through wavelet reconstruction. The results showed that the wavelet transform technique could handle all kinds of background and low signal-to-background ratio spectra, and required no prior knowledge about the sample composition, no selection of suitable background correction points, and no mathematical assumption of the background distribution. This technique performed as well as the conventional three-point background correction method for linear backgrounds, and provided better results than the latter for curved backgrounds. The proposed procedure was illustrated, by processing real spectra, to be an effective and practical tool for background correction in ICP-AES
[en] Calibration is required to obtain analyte concentrations in atomic spectrometry. To take full benefit of it, the adequacy of the coefficient of determination r2 is discussed, and its use is compared with the uncertainty due to the prediction bands of the regression. Also discussed from a tutorial point of view are the influence of the weighting procedure and of different weighting factors, and the comparison between linear and quadratic regression to cope with curvatures. They are illustrated with examples based on the use of ICP-AES with nebulization and laser ablation, and of LIBS. Use of a calibration graph over several orders of magnitude may be problematic as well as the use of a quadratic regression to cope with possible curvatures. Instrument softwares that allow reprocessing of the calibration by selecting standards around the expected analyte concentration are convenient for optimizing the calibration procedure.
[en] Analytical expressions and numerical results describing ionization of atoms by intense linearly polarized ultrashort laser pulses are obtained in the frame of the Keldysh approach. Photoelectron spectra and total ionization probabilities are presented for several analytical models of a single-cycle laser pulse. In particular, strong left-right asymmetry of the spectra is shown for the case of odd pulses.
[en] A new class of charged particle energy analyzers, spheroid energy analyzers (SEA) that are characterized with very high energy resolution and transmission, is presented. A prototype analyzer was built that has achieved a relative energy resolution of 0.05% at a transmission of 21% out of a 2π steradian. A very high order of focusing of these analyzers is presented via simulation that indicates the existence of 13th order focusing in one of our models. This promises further improvements in energy resolution in future practical analyzer embodiments. A novel geometrical framework is presented, which describes SEA analyzers in general terms within which well known types of analyzers CMA and CHA appear to be only particular examples.
[en] A discrete two-hole one-particle (2hlp) shakeup/down state can decay either by spectator Auger transitions or by participant Auger transitions. The 2hlp state created by the participant Auger transition of the 2hlp shakeup/down state can be the same as the one created by the Auger transition of the 1h state. The participant Auger transition by which the electron excited by the shakeup/down fills the core hole, can be dominant. If this is so, when the two discrete core-hole states couple to the same continuum and their separation energy is smaller than or comparable to the core-hole lifetime width, there is a possibility of an interference between the Auger transition of the 1h state and the participant Auger transition of the 2hlp state. The screening of the Auger electron emission of the 1h state via the participant Auger transition of the 2hlp state leads to a pronounced interference in the Auger-electron spectroscopy (AES) spectrum. Because the screening function behaves like a Fano resonance. As the function is critically energy dependent, the photoelectron spectroscopy (PES) line peaks do not coincide with the AES ones, when the latter ones are shifted by the 2h final-state energy. In such a case, the PES line peak measured in coincidence with the AES one is shifted from the noncoincidence PES one. When the photoelectron is collected in coincidence with the Auger electron (or X-ray fluorescence) for a selected decay channel, i.e., when the doubly differential photoionization cross section of the photoelectron and the Auger electron (or X-ray fluorescence) being emitted and collected in coincidence is integrated over the Auger-electron kinetic energies (or X-ray fluorescence energies) of the selected decay channel and summed for the final states of the selected decay channel, the photoelectron spectrum is the noncoincidence (singles) photoelectron spectrum weighted by the branching ratio of the partial decay rate of the selected decay channel so that we can extract the screening function by comparing the coincidence photoelectron spectrum with the singles (noncoincidence) photoelectron one