Kinetic Features of the Radical Species Produced in γ-Irradiated dl-Tartaric Acid and the Dosimetric Potential of this Acid

The room-temperature and high-temperature kinetic features of the radical species produced in solid dl-tartaric acid (dl-TA) gamma-irradiated at room temperature and the dosimetric potential of this acid were investigated in a detailed ESR study. Irradiated dl-TA presents an ESR spectrum with many unresolved resonance lines even at the lowest radiation dose applied (100 Gy). The evolution of the signal intensities associated with induced radical species with microwave power, applied dose and temperature was followed. Three groups of resonance intensities originating from three different radicals exhibiting different spectroscopic features, stabilities at room and high temperatures, and radiation yields were found to take part in the formation of experimental ESR spectrum. These three species were calculated to exhibit spectroscopic features similar to those already reported for X- or gamma-irradiated deuterated single crystals of dl-TA and assigned as I, II and III. The same radical notation was adopted in the present work, and the intensities related to these species were denoted with the names of their corresponding species. Species III, which had the lowest radiation yield and the lowest stability, was observed as a species of four resonance lines. The two inner constituents of these four lines were partially obscured by the two central doublets originating from species I and II. The latter were relatively stable and had activation energies around 35 kJ/mol. The percentage concentrations of the involved species were estimated by comparing experimental and calculated spectra. The reasonably high radical yields of the dl-TA in the dose range of interest, the fairly good stabilities of the species produced (I and II) at room temperature, and the almost linear features of the constructed dose-response curves led us to conclude that the intensities associated with the stable species (I and II) could be used to estimate the applied dose in the dose range of 100 Gy-34 kGy with fairly good accuracy and that dl-TA could be a good candidate for exploring low radiation dose measurements by ESR dosimetry. (C) 2009 by Radiation Research Society