Radiation effects in organic metals: The mechanisms of damage production

Single crystals of several organic conductors have been irradiated with X-rays of several energies. The molecular concentration of defects and damage rates, estimated from the transport properties of the damaged crystals, have been compred to calculated values in order to decide if the damage is proportional to the number of protons displaced by nuclear collisions or to the total energy absorbed by the crystal in the form of electronic excitations. It is demonstrated that, from the point of view of radiation effects, organic metals behave more like normal molecular insulating crystals than like metals. The fraction of destroyed molecules scales with the total absorbed energy. An absorbed energy of 7.1 keV is needed to damage a molecular unit of TMTSF-TCNQ, 21.2 keV for a molecular unit of TTF-TCNQ and 147 keV for a molecular unit of TTT2-I3. The local structures of the molecules are probably responsible for these differences rather than the crystal structures or the electronic metallic properties.