Spectra of soft X ray and EUV emissions of oxygen ions, precipitating into the Jovian atmosphere, are calculated, taking into account the dynamical evolution of the energy and charge distributions of the ions as they propagate. Monte Carlo simulations are performed using experimental and theoretical cross sections of ion collisions with the atmospheric gases. The numbers of X ray and EUV photons produced per precipitating oxygen ion are calculated as functions of the initial ion energy and charge. The energy and charge distribution functions are used to evaluate the intensities of characteristic X ray and EUV emission lines of oxygen ions in Jovian auroras. Radiative cascade transitions from highly excited ion states are shown to be an important source mechanism of soft X ray and ultraviolet emission lines. ¿ 1998 American Geophysical Union