Enhanced electron attachment to Rydberg states in molecular hydrogen volume discharges

We review recent studies on negative ion formation and studies in other are as that are relevant to the role of high-Rydberg states of H-2 and H-3 in h ydrogen negative ion sources. Possible mechanisms for the formation of thes e excited states are discussed, including the formation of long-lived super excited (core-excited) Rydberg states. Experimental evidence for negative i on formation via electron attachment to core-excited Rydberg states in a gl ow discharge apparatus is presented. An expression for the dissociative ele ctron attachment rate constant for Rydberg molecules is derived based on el ectron capture by a Rydberg molecule due to polarization interaction. (C) 1 999 American Institute of Physics. [S0021-8979(99)03310-1].