ION-PAIR FORMATION IN NEAR-THERMAL ENERGY COLLISIONS OF SODIUM CLUSTERS WITH ELECTRON-ACCEPTORS

Sodium clusters (Na-x, x less than or equal to 100) were collided with A = TCNQ, C-84, C-60, Br-2, or SF6 at near-thermal energies under cro ssed beam conditions. Efficient single collisional ionization was obse rved for all A. Resulting cations and anions were studied by mass spec troscopy. Resonant electron transfer followed by charge separation to yield parent cluster cation (Na-x(+)) and anion (A(-)*) pairs is an i mportant channel-given sufficient center of mass kinetic energy. It is the only charging process observed for the fullerenes and TCNQ. For B r-2 and SF6, electron transfer can give rise to either charge separati on or bond reanangement/chemi-ionization. We discuss factors influenci ng the energetics, inelasticity, and probability of electron transfer/ ion-pair formation in these systems. (C) 1998 American Institute of Ph ysics.