Ion Collisions with Rydberg Atoms in Strong Electric Fields

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<~vvₑ<~10 where vₑ=n^-1 a.u. Electric fields which ionize product Rydberg atoms in states n^'=n+Δn with Δn=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.