Atoms in a Rydberg state should be exceptional targets for a strongly-
enhanced electron-capture process in collisions with multicharged ions
since a quadratic increase of the cross section is expected when the
binding energy of the target electron decreases. Simultaneously, becau
se of the quasi-resonance of the capture process, very high orbitals s
hould be populated. Laser excitation of the target atom to a Rydberg s
tate, combined with a new detector based on field ionization and energ
y spectrometry, has made it possible to detect very high Kr7+(n) Rydb
erg states after single electron capture. A wide n distribution, up to
n approximate to 100, of the capture cross section has been observed.
Several collision systems composed of a Kr8+ projectile and a well-de
fined Rydberg state Rb-(n(i)p) of the target atom have been investiga
ted with various kinetic energies and various initial ng states (15 <
n(i) < 25). The production of doubly excited Kr6+*(n(0), n) ions, aft
er a two-electron capture has been investigated as well, and can be ex
plained by two successive collisions with Rb(5s) and Rb(n(i)p) atoms,
leading to n(0) = 10 and a wide distribution of n states.