Fluorescence spectra resulting from extreme ultraviolet photon excitation of a number of molecular systems have been obtained. The final states produced have been determined from the dispersed fluorescence so that the species and the vibronic levels populated could be quantitatively determined. From these data, specific cross sections for the production of excited molecular photofragments have been obtained. In addition, the kinetic energy distribution of excited atomic photofragments following dissociative ionization excitation of molecular nitrogen has been obtained by using a fluorescence photon-photoion coincidence technique. A discussion of the various multichannel processes, their significance, and their relevance to planetary and astronomical problems, together with relevant data are presented.