The classical-trajectory Monte Carlo method has been used to investigate collisions of ions and Rydberg atoms in strong dc electric fields. Cross sections are presented for n = 10 and n = 20 Rydberg atoms at velocities 1 ^ v /ve ^1 0 where ve = n” 1 a.u. Electric fields which ionize product Rydberg atoms in states n’ – n + An with An = 1, 2, and 4 were used. The electric field caused the cross sections for electron capture to decrease by up to fourfold while the ionization values increased by up to two orders of magnitude.
