The formation of hollow ions in dense Z-pinch and laser produced plasmas is
investigated by means of high-resolution X-ray spectroscopy and atomic dat
a calculations. Dense plasma effects are found to result in highly populate
d excited states which open up excitation channels not accessible in low-de
nsity plasma sources. This makes fs-laser radiation interacting with matter
an important tool for modern atomic physics investigations. (C) 2001 Elsev
ier Science B.V. All rights reserved.