Direct and Indirect Action of Radiation | SpringerLink
link.springer.com › chapter › 10If the absorption of radiation occurs in the molecule in which the lesion appears, then this is the direct action of radiation ,while with indirect action the absorption of the radiation energy and the response to this energy occur in different molecules. This definition is considerably more rigorous than the one used in the past, in which the irradiation of dry systems was considered as direct, while the indirect effect was considered to occur predominantly in the presence of water.