Measurement of the O2O3O4 and O3O4O5 super Coster–Kronig rates in tungsten via asymmetric diffraction spectrometry

Abstract

The tungsten Lγ transitions between 11 and 12 keV and Kα transitions from 57 to 60 keV were produced by a laboratory electron-bombarded x-ray source and simultaneously recorded with high resolution by using multiple diffraction planes of the same quartz crystal operating in Cauchois transmission geometry. The W Kα transitions were dispersed by the (5 0 2) planes, which were perpendicular to the crystal entrance surface, and by the (6 0 2), (7 0 2), and (8 0 4) planes which were rotated with respect to the (5 0 2) planes by angles up to 4.80 • . The W Lγ transitions were dispersed by the (2 0 1) planes rotated from the (5 0 2) planes by 4.01 • . The spectra from the five planes were simultaneously recorded on image plate detectors, and spectra were also recorded by scanning solid-state electronic detectors with narrow slits across the spectral lines. The metrology of the L and K shell spectra diffracted from multiple quartz planes enabled the detailed analysis of the detector spatial resolution and accurate measurement of the instrumental broadening produced by the various quartz diffraction planes. The W Lγ spectra had the highest instrumental resolving power, 1800, permitting for the first time the resolution of the blended Lγ 4 (L1O2) and Lγ 4 (L1O3) transitions. After subtracting the instrumental and detector contributions to the line widths, the remainder was assigned to the natural line widths. The measured widths of the O2 and O3 levels were 2.9 eV and 1.9 eV, respectively, and based on atomic code calculations these widths are attributed to the O2O3O4 and O3O4O5 super Coster-Kronig processes. This work demonstrates the ability to simultaneously record high resolution (<1 eV) L and K spectra to determine the line shapes of the heavy elements (e.g. W through Am) by using multiple planes of a single quartz crystal and to accurately measure the non-radiative super Coster-Kronig rates which are closely related to the energy level structure of the outer shells of the heavy elements.

High resolution spectrometer for extended x-ray absorption fine structure measurements in the 6 keV to 15 keV energy range

“…The Lorentzian and Gaussian widths resulting from the spatial resolution of the TR image plate from Ref. 9, corresponding to 0.58 eV ± 0.1 eV Lorentzian and 0.66 eV ± 0.1 eV Gaussian at the Cu K edge, were removed from the fitted Lorentzian and Gaussian widths. The resulting widths are shown in Fig.…”

Measurement of high-energy (10–60 keV) x-ray spectral line widths with eV accuracy

“…These asymmetric planes and rotation angles are (602) and 2.78 • , (702) and 4.80 • , and (804) and −4.01 • . 1 In the small angle approximation, 1, 2 a spectral line is dispersed from the spectrometer axis by the distance x = R c (θ − α), where R c is the crystal bending radius and θ is the Bragg angle with respect to the diffracting planes. Since the asymmetric planes (602), (702), and (804) have larger Miller indices compared to the (502) planes, the lattice spacings are smaller, the Bragg angles are larger for a given x-ray energy, and so the spectral dispersion and resolution are larger.…”

Ultra-thin curved transmission crystals for high resolving power (up to E/ΔE = 6300) x-ray spectroscopy in the 6–13 keV energy range

“…The Cauchois spectrometer has the property that to first order, monoenergetic x-rays from an extended source are focused at one point on the RC, and different energies are dispersed along the RC. Previously, we have used this type of spectrometer to record the W L spectra from electronbombarded tungsten anode sources with resolving power E∕ΔE 1800 [1,2]. In this study, ultra-thin crystals are employed to minimize absorption at the lower energies of interest.…”

“…X-rays having energy E from the extended source are focused on the RC at a distance x R c θ − δ from the spectrometer axis. The dispersion is Δx∕ΔE R c tan θ∕E [1], and high dispersion is achieved by using a large crystal-bending radius R c , within the limitations of the instrument footprint, and large Bragg angle θ that results from small lattice spacing 2d. In addition, the crystal should be sufficiently thin so that attenuation of the x-rays of central energy E is small and sufficiently thick so that the diffraction efficiency is optimal.…”

“…The Lα 1 transition was selected for the evaluation of the crystal's resolving power because it is the most intense of the L transitions, is well isolated from the other intense Lβ and Lγ transitions, and is near the much weaker Lα 2 transition, which provides an excellent energy scale without perturbing the Lα 1 . In addition, the Lα 1 transition originates from the radiative decay of the tightly bound 3d 5∕2 level of W and is unperturbed by multiple vacancies, oxidation, and other material properties of the tungsten anode that might influence the higher-lying levels [1]. Finally, the natural lifetime width of the Lα 1 transition is well known and can be accurately accounted for when determining the crystal's resolving power [6].…”