Near infrared lights emission of 40Ar16+ impacting on metal surfaces

Abstract

The highly charged ion 40 Ar 16+ with the velocity (kinetic energy E K =150 keV, velocity V=8.5×10 5 m/s) smaller than Bohr velocity (V Bohr =2.9×10 6 m/s) was found to hove impacts on the surfaces of metals Ni, Mo, Au and Al, and the Ar atomic infrared light lines and X-rays spectra were simultaneously measured. The experimental results show that the highly charged ion that captures electrons is neutralized, and the multiply-excited hollow atom forms. The hollow atom cascade decay radiates lights from infrared to X-ray spectrum. The intensity of infrared lights shows that the metallic work functions play an important role in the neutralization process of highly charged ions during their interaction with metallic surfaces, which verifies the classical over-the-barrier model. infrared light lines, X-ray, neutralization, highly charged ionsThe interaction of slow highly charged ions with solid surfaces has recently drawn considerable interest [1][2][3] . The study shows that during the impact of the highly charged ions with the velocity smaller than the Bohr velocity (V Bohr = 2.9×10 6 m/s) on the metal surface, metallic target electrons move faster than the projectile and readily react to perturbation. The ion could be rapidly neutralized (10 −15 s) by capturing conducting-band electrons in the metal. The captured electron comes into high Rydberg states with empty or only sparsely populated inner shells, leading to the formation of hollow atoms [4] . These very excited states of short lifetime then rapidly decay via ionization, Auger process and light emission.