We report nanometer‐sized silicon (Si) crystallites prepared by excimer laser ablation in constant pressure inert gas ambient. Size distribution of the Si ultrafine particles depends on the pressure of inert gas ambients. The relation between the average size and the ambient pressure can be explained by an inertia fluid model. It is verified that the size of the Si ultrafine particles is ∼3 nm and greater in diameter. Furthermore, crystallinity of the nanoscale ultrafine particles is crystalline similar to that of bulk Si. ©1996 American Institute of Physics.