| Collisions between atoms in high Rydberg states and polar targets can lead to the formation of dipole-bound negative ions. We examine the dynamics of CH3CN- ion production through electron transfer in K(np)/CH3CN collisions using velocity selected Rydberg atoms. The CH3CN- ion formation rate decreases markedly with decreasing Rydberg atom velocity, principally as a consequence of postattachment electrostatic interactions between the product ions. Implemented using Monte Carlo techniques, a curve-crossing model, which considers the effect of crossings between the diabetic potential curves for the covalent K(np)/CH3CN system and the K+/CH3CN - system, provides a clear explanation of several characteristics seen in electron transfer in K(np)/CH3CN collisions including: the n dependence in the CH3CN- ion production rate, the velocity dependence in the CH3CN- ion production rate, and the relatively small rate constant ∼0.5 - 1.0 x 10-8cm3 s-1 for production of long-lived CH3CN - ions. |
