The internal and translational energy distributions of the OD X (2) Pi
photofragment resulting from the 218 nm photolysis of acetic acid-d a
re presented. Comparison of these results with those of acetic acid-h
photolysis reveals the effects of isotopic substitution on the alpha-c
leavage photodynamics of (1)(n, pi)-excited acetic acid. The OD produ
ct contains only approximately 17% more rotational energy than the cor
responding OH fragment, and the OD translational energy distributions
broaden with increasing fragment rotational level. A pure impulsive mo
del for the dissociation dynamics is inadequate to explain these resul
ts. Interpretations which also include contributions from excited stat
e bending motions may be more realistic.