Influence of chemical effects on Al high-resolution Kα X-ray spectra in proton and alpha particle induced X-ray spectra

Abstract

Kα X-ray emission induced by 2 MeV protons and 3 MeV He ions in thick pelletized Al metal, Al₂O₃, Al₂S₃, AlN, AlPO₄ was measured using a wavelength-dispersive spectrometer with a flat diffraction crystal to study the chemical sensitivity of related X-ray spectra. The energy shifts and relative intensities of KαL¹ multiple ionization satellites were determined for proton excitation. For He excitation we were able to study KαL¹, KαL² and KαL³ multiple ionization satellite components of Al Kα spectra. Intensity ratios of two major KαL¹ components (Kα₃ and Kα₄) were determined for both 2 MeV proton and 3 MeV He excitations. Relative intensities of Kα diagram lines (KαL⁰) and KαL¹, KαL² and KαL³ multiple ionization satellites were determined for 3 MeV He excitation. The energy shifts of Kα_1,2 and multiple ionization satellite (MIS) peaks were determined using the spectra obtained from the Al and Al compounds mixed with MgBr, where Br Lα and Lβ peaks were used as internal calibration standards. The results confirm statistically relevant energy shifts for Al Kα_1,2 X-ray peaks from the measured compounds. The Al Kα_1,2 energy shifts show a linear decrease with the increase of the calculated effective charge on Al atoms. Similar linear dependances of the peak energy shift vs. the effective charge on Al atoms have been observed on KαL¹ multiple ionization satellite components Kα′ and Kα₄ measured by 3 MeV He excitation. The work reported here demonstrates the importance of studying chemical effects of the Kα X-ray band for low-Z elements and suggests future directions for the construction of an extensive and accurate database of diagram lines and related multiple ionization satellites for proton and He ion excitation in the MeV energy range.