Rydberg to plasma evolution in a dense gas of very excited atoms

Abstract

A Rydberg atom gas quickly evolves into a plasma above a threshold density. The process is attributed to Rydberg-Rydberg and Rydberg-electron collisions occurring faster than the medium expansion. Observations are found in good agreement with a simple rate equation model. This effect is different from a Mott transition. Conditions for the occurrence of this latter effect in a Rydberg atom gas are briefly discussed.