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 . This behaviour could be theoretically well described by the transient formation of an electronically excited ion Na2- * (called also ? resonance) in the repulsive A 2Sg+state with vibrational level dependent coupling to the Na2 ground electronic X 1Sg+ 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.