A new formulation of the base rate and the adiabatic energy correction used in the energy corrected sudden approximation is proposed. Explicitly, the common energy gap laws are replaced with an angular momentum gap law. This law is based upon the introduction of an effective angular momentum parameter (l(c) - 2h) limiting the collision-induced intra-molecular rotational energy transfer (RET) due to the finite interaction time. The experimental results of collision induced RET for the N-2-N-2, CO-CO and N-2-He systems obtained by the application of femtosecond coherent anti-Stokes Raman spectroscopy (fs-CARS) are in excellent agreement with the proposed model. (C) 2003 Elsevier Science B.V. All rights reserved.