Quantum tunnelling and classical above-barrier transitions in electron detachment from negative ions by negatively charged projectiles

A simple model of electron detachment from negative ions by negatively charged projectile impact is developed as a combination of quantum tunnelling and classical field ionization. While the tunnelling theory has been discussed previously by Smirnov and Chibisov, we have substantially amended Solov'ev's classical model for above-barrier transition. As the most important modification we introduce the concept of decay rate for the classical ensemble related to the quantum state and evaluate the rate in terms of the simple free-fall atomic model. The present theory compares very well with recent experiments while the isolated application of the tunnelling model and of the classical model yields results that are a factor of two too large and too small, respectively.