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Abstract

It is of great importance to study the alignment of atoms in collision process in elementary analysis with a Particle Induced X-ray Emission (PIXE) technique. The measurement of alignment can also offer an effective testing ground for developing theory models in ionization process. The typical L X-ray spectra are measured for Ag thin target by 15 keV electron impact at emission angles from 0° to 25°. Angular dependence of intensity ratios L_α/L_β1, L_β2/L_β1 and L_γ/L_β1 are investigated as a function of the second-order Legendre polynomial P₂(cosθ). This study found that L_β2 line exhibits anisotropic emission spatially, while the emission of L_α, L_β1 and L_γ1 lines is isotropic. The results are interpreted by the influence of the Coster-Kronig (CK) transitions on the spatial distribution of X-ray emission. The anisotropy parameter β for L_β2 lines is obtained experimentally and consequently the alignment degree A₂₀ for L₃ subshell is determined by taking CK transition into account. Namely, the alignment does exist in L₃-subshell for atomic ionization by electron impact. The measurements offer an evidence to the existence of alignment for atomic ionization in electron-impact process.

Keywords

X-ray angular distribution particle induced X-ray emission (PIXE)electron impact alignment of atoms

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L 3 -subshell alignment of Ag in collision with 15 keV electrons

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