Long-Lived Electron Spin Resonances in Rats Irradiated at Room Temperature

to be very reactive, disappearing in microseconds after the irradiation (1). Within the same magnitude of time essentially all the energy of the radiation is said to reach its final chemical form. In contrast to these assumptions, studies in this laboratory indicate that unpaired species in at least one irradiated mammalian tissue (bone) do exist for prolonged periods. This observation suggests that some energy from ionizing radiation may be available for considerable periods after the irradiation of tissue. The existence of relatively stable radiation-induced electron spin resonances also offers the possibility of an in vivo dosimeter for accidental radiation exposures to X- or y-rays. METHODS