X-ray emission of exotic ions in dense plasmas

Hollow ion X-ray emission has been observed in experiments studying interaction of heavy ion beams with solids and their occurrence has been ascribed to charge exchange processes occurring when highly charged ions interact with a metal surface. In high temperature high-density plasmas, like, e.g., high intensity laser produced plasmas or high current Z-pinches, numerous researchers have reported about “exotic” X-ray transitions of hollow ions: K0LX →K1LX−1+hνhollow. Although atomic structure calculations seem to confirm that measured line positions correspond to transitions in hollow ions, line identification is difficult and the observed high intensity remains a mystery (by orders of magnitude) up to present days.