- Abstract The bending dynamics of acetylene undergo a normal-to-local transition in the vicinity of twelve quanta of excitation. We report the observation, by stimulated emission pumping, of the first few eigenstates exhibiting local-mode behavior. Assignments are made on the basis of complementary information in spectra recorded from intermediate levels with gerade and ungerade vibrational symmetry. The highest energy state currently assigned (N bend= 16) is characterized by a large (> 75^ o) distortion from the linear geometry at its classical turning point. Large geometrical distortions will lead to unique electronic, collisional, and chemical properties for these eigenstates.