2.1. Attachment of free electrons

In our earlier experimental studies we have shown that dissociative attachment of free low-energy electrons to Na₂ molecules in the electronic ground state depends not only on the electron energy, but also drastically on the vibrational excitation of the molecule [1]. This behaviour could be theoretically well described by the transient formation of an electronically excited  ion Na₂^- * (called also ? resonance) in the repulsive A ²S_g⁺state with vibrational level dependent coupling to the Na₂ ground electronic X ¹S_g⁺ state.This transient ion either decays through the emission of the electron, possibly leaving the neutral molecule in a vibrationally excited state v*, or dissociates into Na^- and Na fragments:

The branching ratio of both channels is strongly dependent on the vibrational level v" excited in Na₂ before the collision.

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