Surface Plasmon-Assisted Excitation of Atomic Visible Light Spectral Lines in the Impact of Highly Charged Ions ¹²⁶Xe^q+ on Solid Surfaces

We measured the visible light spectral lines of sputtering atoms from solid surfaces of Al, Ti, Ni, Ta and Au which are impacted by 150 keV ¹²⁶Xe^q+ (6 ≤ q ≤ 30). It is found that intensities of the light spectral lines are greatly and suddenly enhanced when the charge state of the ion is raised up to a critical value. If assuming that potential energy released from the incident ion due to capturing one electron is enough to excite a surface plasmon, we can estimate the critical charge states and obtain the results very well consistent with the measurements for the above mentioned target materials. This means that a surface plasmon induced by one electron capture can enhance the excitation of atomic visible light spectral lines in the impact of a highly charged ion on a solid surface.