Proton-induced x-ray production cross section for the Ar- K shell measured using a gaseous Ar target confined in crystalline Si

Abstract

The measurement of the x-ray production cross sections of the noble gases by proton impact has always been challenging. This is due to their insolubility and their impossibility to form compounds, which requires a complex experimental setup that enables the insertion of a controlled gas jet in vacuum. In this communication, an alternative method involving gaseous nanometer-thick blisters implanted in a crystal surface region is reviewed. To this end, Ar+ ions were implanted in Si single crystals, thus producing confined high-pressure Ar blisters just below the Si(1 1 1) surface. The surface composition and stability of these samples was analyzed by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry, respectively. The thin-target approximation was employed to deduce the Ar-𝐾 x-ray production cross section for 0.3 MeV to 3.0 MeV protons. The comparison with data from the literature and theoretical calculations based on the plane-wave Born approximation with corrections confirms the efficacy of the method. These results might be helpful in the development of a simple and reliable way to measure x-ray production cross sections of the noble gases. Besides, owing to the great stability of the samples, they could be used to produce noble-gas standards.