A laser ablation supersonic expansion source is used to deposit self-supporting thin films of agglomerated Si nanocrystallites. Average particle size is controlled through variation of deposition process parameters, including relative ablation pulse/gas valve timing and interaction channel length, as well as post-deposition processing steps, including repeated HF etch/oxide regrowth cycles, and oxidation furnace treatments. Films are characterized using photoluminescence (PL) emission spectroscopy. Clear spectral trends in the PL emission data point to a correlation between process parameter control, mean particle size, and peak PL wavelength. We conclude that quantum size effects play a critical role in defining the PL emission wavelength of Si nanocrystallites.