[en] Average energy-transfer values are reported from trajectory studies of Xe and He colliding with highly excited azulene-d₀ and azulene-d₈. The calculated isotope effect is small, in agreement with experiments on related systems. This suggests that the low-frequency modes are important in determining the amount of energy transfer. Furthermore, the fact that both calculated and observed changes with deuteration are small for helium suggests that the classical description of the energy transfer is adequate. The biased random walk model for collisional energy transferred is found to reproduce the observation of a small isotope effect. The calculated fraction and magnitude of supercollisions are in accord with extant data and are predicted to be relatively unaffected by deuteration. 33 refs., 2 figs., 2 tabs