In contrast to the photoexcitation of hydroxyacetone (HA) at 193 nm resulting in an instantaneous dissociation of the Rydberg ¹(n,3s) state, on photoexcitation at 248 nm the singlet ¹(n,π*) excited HA molecule first undergoes intersystem crossing (ISC) to the triplet state, followed by a minor dissociation channel to CH₃COCH₂ and OH radicals. The real time formation of OH, which is probed by laser-induced fluorescence (LIF), shows a rate constant to be ≥10⁸s⁻1. The initial rotational state distribution of OH(X²Π) is found to be Boltzmann-like, characterized by a single rotational temperature T_rot of 450±40 K. The average relative translational energy of the photofragments is determined by Doppler spectroscopy to be 8.7±2.0kcal mol⁻¹. The observation of OH with a modest rotational energy, no vibrational energy, and a large amount of translational energy suggests significant exit energy barrier with the dissociating surface.