Experimental measurement of state selective double electron capture in 1.4-20 keV/u Ar<sup>8+</sup> collision with He

Abstract

Electron(s) capture in highly charged ions collision with atoms and molecules is a fundamental process related to the electron transition between bound states belongs to two atomic-centers. The X-ray emission following electron capture is important for X-ray astrophysical modeling, fusion plasma diagnosing, and ion irradiated biophysics. Over past decades, momentum-imaging cold-target recoil ion momentum spectroscopy is one of significantly developed techniques and has been widely applied to measure the quantum state-selective population in electron(s) capture processes. Based on the cold target recoil ion momentum spectroscopy mounted at the 150 kV highly charged ion platform in Fudan University, the state-selectivity of double electron capture in 1.4-20 keV/u Ar<sup>8+</sup> on He collision was measured, and the relative cross sections of the 3<i>l</i>3<i>l</i>’to 3<i>l</i>7<i>l</i>’ double excited states were obtained. It is found that with the increase of collision energy, more quantum state-selectivity channels are open in the double electron capture (DEC) of Ar<sup>8+</sup>-He collision. It is also found that the relative cross section of the quantum state population is strongly dependent on the collision energy of the projectile ion. This present measurement not only enriches the state-selective cross-section repository and collision dynamics for highly charged ion charge exchange processes, but also provides experimental benchmarks for the available theoretical calculations.