1. A method for marking an item comprising at least the steps of: depositing by evaporation a lithium fluoride film having a thickness of at least 20 nm obtained by evaporating the same on the item or on a mark support to be applied to the item to be marked; irradiating the previously obtained lithium fluoride film by means of a ionising radiation beam having an energy of at least 0.4 keV controlled by computerised means to carry out the desired identification mark, wherein the depositing step is performed at an atmospheric pressure and in an atmosphere consisting of air or nitrogen.