The previous quantum mechanical close-coupling study of the dissociati
ve collisions in He+H-2 (T-shape configuration) by the present authors
[Chem. Phys. Letters 216 (1993) 613] has been extended to a wide rang
e of the total energy 4.8-7.5 eV. The dissociation process shows a cle
ar vibrational enhancement. The dissociation probability has an undula
tion as a function of the total energy, and by using classical S-matri
x theory it is shown that this feature is caused by interference of th
e contributions of multiple trajectories.