We demonstrate the excitation of a molecular vibrational coherence via impulsive stimulated Raman scattering (ISRS) by using a pump pulse longer than the vibrational period of the excited mode. By making use of the reshaping of the pump pulse during nonlinear propagation, a Raman vibrational coherence can be excited via ISRS with a pump pulse incapable of such excitation at the input of the medium. (C) 2003 Elsevier Science B.V. All rights reserved.