The photofragment excitation spectra for O(D-1) production from the 317-327 nm photolysis of ozone under supersonic free-jet and low-temperature flow conditions show structure superimposed on an underlying continuum. Doppler profiles of the nascent O(D-1) photofragments confirm that the O(D-1) formed by photolysis at the wavelengths of the peaks in the photofragment excitation spectrum arises from the hitherto unobserved spin-forbidden predissociaton to O(D-1) + O-2(X(3) Sigma(g)(-)) products.