Atomization mechanisms of copper, platinum, iridium and manganese were studied by taking into account several parameters affecting the number of gaseous atoms present in the atomizer. The contributions of thermal expansion and diffusion to the dissipation rate of atoms were investigated. It was observed that the dissipation process cannot be described by diffusion only. Thermal expansion substantially contributed to the removal of atoms from the furnace and should not be ignored. It was possible to decide to what extent the several processes affect the concentration of the gaseous atoms at any time. From the E(a) values obtained for the elements studied, the last step leading to gaseous atoms for copper, platinum and iridium was found to be the thermal dissociation of dimers in the gas phase; for manganese this was the dissociation of its monoxide in the gas phase.