Thermal spike effect on defect evolution in NaCl irradiated with light and heavy ions at 8 and 300 K

Abstract

Single crystals of NaCl were irradiated at room temperature and at 8K with energetic heavy ions (12C, 50Ti, 58Ni, 74Kr, 152Sm, 197Au, 208Pb and 238U) of 50–2600MeV providing mean electronic energy loss values from 0.7 to 19keV/nm. The creation and evolution of color centers were investigated as a function of fluence and temperature by in situ absorption spectroscopy and thermo-stimulated luminescence, complemented by thermal annealing and optical bleaching. For irradiations at 8K, primary hole centers are observed which typically annihilate at temperatures between 10 and 80K. The efficiency of color center creation at 8K strongly depends on the energy loss of the ions and is several times higher for U and Au ions than for C and Ti ions. Thermal spike estimations, taking into account the finite velocity of heat propagation, assign these effects to thermal stimulated separation of color centers in the genetic Frenkel pairs.