Formation of Na3<\sub>+ by associative ionization in collisions of Na* and Na2(v") A.Ekers, O.Kaufmann, M.Keil, and K.Bergmann Fachbereich Physik der Universitaet, 67653 Kaiserslautern, Germany The vibrational dependence of the rate of Na3+ formation in collisions of Na(nl) and Na2 is studied. While no significant v" dependence is found for (nl)=(5s) and (4d), a marked change of the ion formation is observed for the processes Na(3d) + Na2(X1Sg+, v">25) and Na(3p) + Na2(A1Su+, v'>10). The total (electronic and vibrational) energy, at which the change in the two processes occurs is approximately the same. We speculate that the opening of a new eletronic channel is responsible for this observation.