The transient four-wave mixing signal from a three-level system coupled to a bath of harmonic oscillators is calculated in the short-pulse limit and analyzed at short times. The two excited states of the system are coupled by a constant nonadiabatic interaction V which is treated exactly. This allows an examination of the influence of V on the dynamics in the excited levels at short times. We show that the positions of the minima of the potential energy surfaces of the excited states with respect to the one of the fundamental state play an important role in the relaxation processes. We also show that for high nonadiabatic coupling it is possible to minimize the effect of the bath and hence to minimize, at short times, the coherence losses of the system. The identification of the molecular parameters required to take advantage of this effect should be of interest in the selection of materials for applications in nonlinear optics. (C) 2003 American Institute of Physics.