The properties of long-lived parent anions formed by electron transfer in collisions between K(np) Rydberg atoms and CS2 molecules are investigated. Collisions give rise to two groups of CS2- ions, one that undergoes electric-field-induced detachment in fields of less than or similar to 3 kV cm(-1), the other requiring fields of similar to10-20 kV cm(-1). Measurements using a Penning ion trap indicate that ions, in both groups undergo autodetachment and radiative stabilization. The autodetachment rate for those ions that detach in low (high) fields is similar to5 x 10(2) s(-1) (1.1 x 10(2) s(-1)). The corresponding radiative stabilization rates are similar to4.7 x 10(2) s(-1) (2.8 x 10(2) s(-1)). (C) 2003 Elsevier Science B.V. All rights reserved.