Dissociative charge transfer from highly excited Na Rydberg atoms to vibrationally excited Na₂ molecules

We report the observation of the vibrational dependence of dissociative charge transfer (DCT), Na₂(X¹Σ_g⁺, v″) + Na**(nl) → Na^- + Na + Na⁺, in a single Na/Na₂ supersonic beam at low intrabeam collision energies (1.6 meV) using the STIRAP technique for selective vibrational excitation of Na₂ in the electronic ground state and time-of-flight mass analysis of the ions. The efficiency of this process increases by about an order of magnitude in the range 13 ≤ v″ ≤ 22. Some perspectives are discussed regarding the implementation of a field-free ion-imaging technique for the detection of ions that will allow the direct determination of the kinetic energy distributions of product negative ions and thus distinguish among different possible mechanisms of the DCT process. The first results of test experiments on imaging of photodissociation products of Na₂(v″) without an extraction field are presented, confirming the potential of the new detection concept.