Production and properties of dipole-bound negative ions

The properties of dipole-bound CH3CN− ions formed in collisions between K(np) Rydberg atoms and CH3CN molecules are investigated. The data show that rotationally excited target molecules can form dipole-bound ions. Studies of electric-field-induced detachment point to an electron binding energy of ≈ 11 meV and demonstrate that the characteristics of this process are not strongly dependent on the rotational state of the ion. Measurements also reveal that the weakly bound electron can be removed by collisions with CH3CN, with other polar targets, and with SF6, and possible mechanisms for this are discussed.