Field-ionizing lens system for the detection of high Rydberg states in multicharged ions of keV energies

Abstract

A new detector for state analysis of multicharged ions, excited in high Rydberg states, at kinetic energies of the order of keV is described. It is composed of a field-ionizing lens system (FILS), associated with two electrostatic spectrometers; the first one, in front of the FILS, selects the q-times charged excited ions of interest, and the second one, behind the FILS, analyzes the (q+1)-times charged ions resulting from field ionization according to their kinetic energy. The principle of the FILS is to generate a linearly increasing electric field, colinear with the excited ion beam, that the excited multicharged ions experience until they are field ionized. This detector has been successfully used to detect for the first time the distributions of very high Rydberg n states in the domain n=67–100 produced in Kr7+*(n) ions by electron capture into Kr8+ from laser-excited Rb*(nip) atoms.