Dissociative attachment of low-energy electrons to vibrationally excited molecules using a photoelectron source

The process of dissociative attachment (DA) of low-energy electrons ) to vibrationally excited sodium dimer molecules is studied with high electron energy resolution () in a supersonic molecular beam. A novel photoelectron source, based on two-step photoionization of the sodium atoms in the beam, may deliver a current of up to 1 nA and has been used with a current of typically 0.2 nA in this experiment. The energy dependence of the rate of sodium anion formation is determined by ion detection based on a time-of-flight analysis. The molecules are selectively excited to levels using the technique of coherent population transfer by delayed pulses (STIRAP). The comparison of the experimental data with recent resonance model calculations based on improved potential curves reveals generally good agreement for levels v ”>12. For some distinct differences between theoretical and experimental results persist. Received: 21 November 1998 / Received in final form: 7 April 1999