The time-dependent wavepacket method is used to study the associative ionization process N + O -> NO+ + e(-). We make use of the sudden approximation, effectively assuming that the ionization process itself is fast with respect to the timescale of the motion of the wavepacket and we calculate probabilities and cross-sections for transition to various rovibrational levels of the NO+ ion. The dependence of these quantities on the initial collision energy and the initial partial wave singles out interesting three-dimensional effects which we interpret here. (C) 2012 Published by Elsevier B.V.