EELS white line intensities calculated for the 3d and 4d metals

Author(s):  
C. C. Ahn ◽  
D. H. Pearson ◽  
P. Rez ◽  
B. Fultz

Previous experimental measurements of the total white line intensities from L2,3 energy loss spectra of 3d transition metals reported a linear dependence of the white line intensity on 3d occupancy. These results are inconsistent, however, with behavior inferred from relativistic one electron Dirac-Fock calculations, which show an initial increase followed by a decrease of total white line intensity across the 3d series. This inconsistency with experimental data is especially puzzling in light of work by Thole, et al., which successfully calculates x-ray absorption spectra of the lanthanide M4,5 white lines by employing a less rigorous Hartree-Fock calculation with relativistic corrections based on the work of Cowan. When restricted to transitions allowed by dipole selection rules, the calculated spectra of the lanthanide M4,5 white lines show a decreasing intensity as a function of Z that was consistent with the available experimental data.Here we report the results of Dirac-Fock calculations of the L2,3 white lines of the 3d and 4d elements, and compare the results to the experimental work of Pearson et al. In a previous study, similar calculations helped to account for the non-statistical behavior of L3/L2 ratios of the 3d metals. We assumed that all metals had a single 4s electron. Because these calculations provide absolute transition probabilities, to compare the calculated white line intensities to the experimental data, we normalized the calculated intensities to the intensity of the continuum above the L3 edges. The continuum intensity was obtained by Hartree-Slater calculations, and the normalization factor for the white line intensities was the integrated intensity in an energy window of fixed width and position above the L3 edge of each element.

1994 ◽  
Vol 72 (1-2) ◽  
pp. 57-60 ◽  
Author(s):  
A. M. Gonzalez ◽  
M. Ortiz ◽  
J. Campos

Relative transition probabilities for 43 lines arising from the 3d4 4p configuration of Cr(II) with cores 3d4 (5D), 3d4 (3P), and 3d4 (3H) were determined from measurements of emission-line intensities in a laser produced plasma. This experiment was carried out with Al–Cr alloys with a Cr content of about 0.1%, in order to have an optically thin plasma. Transition probabilities were placed on an absolute scale by using, where possible, accurate experimental lifetimes from the literature and line-strength sum rules. Comparison of the present results with the available theoretical and experimental data are made.


1974 ◽  
Vol 52 (9) ◽  
pp. 786-794 ◽  
Author(s):  
K-H. Tan ◽  
F. G. Donaldson ◽  
J. W. McConkey

Polarization free measurements are presented of the excitation of the 3s3p62S and 3s23p44s2P levels of Ar+ by electron impact. Line intensity measurements yielded relative transition probabilities in good agreement with the recent calculations of Luyken. A double peaked structure is demonstrated to be a common feature of the excitation functions and reasons for this are discussed. Cascade is shown to be an important excitation process for the 4s levels. Comparison is made with other work where available. As a means of calibration of some of the Ar line intensities, a careful measurement was made of the 736 Å Ne excitation function using the Bethe normalization procedure and the known optical oscillator strength.


1977 ◽  
Vol 32 (1) ◽  
pp. 21-27 ◽  
Author(s):  
K. Erhardt ◽  
I. Meyer ◽  
P. Stritzke

Abstract The continuum emission of an argon-and nitrogen plasma developed in an electrical discharge has been investigated in the wavelength range from 3000 Å to 6700 Å. To this purpose the time-and radial dependent plasma parameters such as temperature and the total pressure have been determined in the high conducting stage of the spark by measuring several line intensities. The continuum coefficient was calculated from these data according to the Kramers-Unsöld theory. The comparison of the theoretical and the measured values shows deviations which are discussed. In the case of the argon continuum the ξ-factors for T = 14 000 K agree with the calculated values of Schlüter and the experimental ones of Schulz-Gulde. In the case of the nitrogen plasma the ξ-fac­tors have been determined in the temperature interval from 18 000 K to 45 000 K. Since at these temperatures the particles NII-NIV contribute to the total continuum coefficient, the measured ξ-factors can only be correlated to ξII, ξIII, ... in a narrow temperature range. The measured cor­rection factor ξ for λ = 5050 Å has been applied to determine the temperatures and the pressure of a laser produced spark. The plasma parameters agree with those determined by measuring the line-intensity of the NII-line at 5000 A.


2019 ◽  
Vol 17 (42) ◽  
pp. 27-41
Author(s):  
NOORI S. Manie

In the present work, the nuclear shell model with Hartree–Fock (HF) calculations have been used to investigate the nuclear structure of 24Mg nucleus. Particularly, elastic and inelastic electron scattering form factors and transition probabilities have been calculated for low-lying positive and negative states. The sd and sdpf shell model spaces have been used to calculate the one-body density matrix elements (OBDM) for positive and negative parity states respectively. Skyrme-Hartree-Fock (SHF) with different parameterizations has been tested with shell model calculation as a single particle potential for reproducing the experimental data along with a harmonic oscillator (HO) and Woods-Saxon (WS) single-particle potentials. The effect of the nuclear effective charge has been implemented via using different folding models; valance, Tassie and Bohr-Mottelson. The evaluated results have been discussed and compared with available experimental data.


Author(s):  
Douglas H. Pearson

A feature of considerable interest in the electron energy loss spectra of transition metals is the L23 edge which is composed of two sharp “white lines” superimposed on a broad edge that makes up the trailing background. The white lines are due to the excitations of electrons from filled 2p1/2 and 2p3/2 states to unoccupied 3d or 4d states, and the background intensity is due to continuum excitations. Recent work on the white lines of the 3d transition metals has shown that when normalized to the continuum excitations, the total white line intensity decreases nearly linearly with atomic number (or d band occupancy) across the 3d series. Furthermore, this linear relationship may be used to measure the changes in 3d state occupancy local to specific atoms during alloying and during solid state phase transformations. In the present paper the experimental analysis of the white lines is extended to the 4d transition metals and is then compared to experimental results from the 3d metals.Electron-transparent specimens of the pure 4d metals were prepared by standard electropolishing and evaporation techniques. To prevent oxidation of the Yttrium specimen, however, a 40 nm film of Yttrium was deposited between 15 nm films of Vanadium by direct current ion sputtering in a chamber with a base pressure of < 1.0 × 10−7 Torr. Energy loss spectra were obtained using a Gatan 607 electron energy loss spectrometer attached to a Philips EM 430 electron microscope operating in image mode at 200 kV.


Author(s):  
D. H. Pearson ◽  
C. C. Ahn ◽  
B. Fultz ◽  
P. Rez

A straightforward method for measuring the white line intensities of the L23 absorption edges of 3d transition metal electron energy loss spectra was recently reported by Pearson et al. [1]. In that analysis, the white line intensities were isolated by assuming that the continuum contribution for the 3d metals could be approximated by an edge shape similiar to that of copper, which has a full 3d band. When normalized to the continuum, the white line intensities were found to decrease linearly with atomic number (or 3d state occupancy). A similar analysis for the 4d metals showed that the white line intensities initially increased, peaked at Nb, and then decreased nearly linearly with atomic number [2]. The white line calculations of Ahn et al. were in qualitative agreement with these results for the 4d metals, but deviated from experimental results for the early 3d metals [3]. In an effort to determine if the continuum L23 edge is indeed copper-like for the early 3d metals we have calculated the continuum edge shapes based on an atomic, one electron model.


1985 ◽  
Vol 63 (11) ◽  
pp. 1389-1392 ◽  
Author(s):  
I. Tanarro ◽  
J. Campos

Relative transition probabilities for the infrared lines 3p–4s of Ne I and 4p–5s of Ar I have been determined from emission line-intensity measurements of optically thin light sources. In this experiment a photoconductive cell and a digital phase-sensitive amplifier have been used for light detection. Transition probabilities have been put on an absolute scale by using the Coulomb approximation. The present experimental data are compared with the existing theoretical data for neon and with experimental and theoretical data for argon.


Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 48
Author(s):  
M. Raineri ◽  
M. Gallardo ◽  
J. Reyna Almandos ◽  
A. G. Trigueiros ◽  
C. J. B. Pagan

A capillary pulsed-discharge and a theta-pinch were used to record Kr spectra in the region of 330–4800 Å. A set of 168 transitions of these spectra were classified for the first time. We extended the analysis to twenty-five new energy levels belonging to 3s23p24d, 3s23p25d even configurations. We calculated weighted transition probabilities (gA) for all of the experimentally observed lines and lifetimes for new energy levels using a relativistic Hartree–Fock method, including core-polarization effects.


2007 ◽  
Vol 21 (13n14) ◽  
pp. 2204-2214 ◽  
Author(s):  
BEATE PAULUS

The method of increments is a wavefunction-based ab initio correlation method for solids, which explicitly calculates the many-body wavefunction of the system. After a Hartree-Fock treatment of the infinite system the correlation energy of the solid is expanded in terms of localised orbitals or of a group of localised orbitals. The method of increments has been applied to a great variety of materials with a band gap, but in this paper the extension to metals is described. The application to solid mercury is presented, where we achieve very good agreement of the calculated ground-state properties with the experimental data.


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