Interaction of Fast Ion Beams with Low- and High-Density Targets

are considered in collisions of fast positive ions X with lowand high-density targets A. In the case of a lowdensity, the electron-capture cross section σec(n) has a certain distribution over the principal quantum number n with a maximum at n = nmax and asymptotic behavior σec(n) ≈ n−3 at n nmax. For Rydberg states n 1, ions with the orbital quantum numbers = 0 and 1 are created with the highest probability (see, e.g. [1]). The distribution of σec over n states depends not only on the relative velocity v and the atomic structure of colliding systems but also on the target density. In a dense target, the maximum possible principal quantum number ncut which the X(q−1)+(n) ion can be created with, is limited because the population of highly excited n states is destroyed by ionization collisions with the target: