An analytical formula for the Barkas correction to the theory of ion stopping

Nonperturbative methods of nonrelativistic quantum mechanics have been used to obtain a simple analytical form of the Barkas correction to the stopping factor for arbitrary values of the charge of projectile ion and collision velocities greater than or comparable with atomic values. The proposed theory involves the notion of the effective interaction radius that is borrowed from the well-known Bohr theory of stopping of fast charged particles.