Positron annihilation in colourless centres in heavily gamma-irradiated NaCl

F.J.NAVARRO; L. C. DAMONTE; J.L.ALVAREZ RIVAS; J.RIVAS; J.L.FERRERO

JOURNAL OF PHYSICS CONDENSED MATTER

IOP

Año: 1995 vol. 7 p. 8273 - 8278

0953-8984

A detailed study of posivon lifetimes in heavily ga"a-inadiared NaU single crystals, which undergo a pulsed thermal annealing treatment up to 740 T. is presented. Above 300 "C at which temperature the samples ae completely bleached, two exponential terms suffice to fit lhe lifetime curve. While the shortest lifetime q does not depend upon the annealing temperalure and has a value close to that found in unirradiated samples. the olher lifetime rzdetailed study of posivon lifetimes in heavily ga"a-inadiared NaU single crystals, which undergo a pulsed thermal annealing treatment up to 740 T. is presented. Above 300 "C at which temperature the samples ae completely bleached, two exponential terms suffice to fit lhe lifetime curve. While the shortest lifetime q does not depend upon the annealing temperalure and has a value close to that found in unirradiated samples. the olher lifetime rzto 740 T. is presented. Above 300 "C at which temperature the samples ae completely bleached, two exponential terms suffice to fit lhe lifetime curve. While the shortest lifetime q does not depend upon the annealing temperalure and has a value close to that found in unirradiated samples. the olher lifetime rz"C at which temperature the samples ae completely bleached, two exponential terms suffice to fit lhe lifetime curve. While the shortest lifetime q does not depend upon the annealing temperalure and has a value close to that found in unirradiated samples. the olher lifetime rzfit lhe lifetime curve. While the shortest lifetime q does not depend upon the annealing temperalure and has a value close to that found in unirradiated samples. the olher lifetime rzhas a value close to that found in unirradiated samples. the olher lifetime rz exhibits a monotonic increase with annealing temperature and two recovery stages at about 340a monotonic increase with annealing temperature and two recovery stages at about 340 and 540 T, This pattern parallels the thermal recovery of the ionic conductivity of~irradialed NaCI. It is suggested that n reflects the annihilation of positrons at cation vacancies thermally released from radialion-induced divacancis. The 72 evolution with the annealing temperature has been analysed in terms of a trapping model and a value of 1.96&0.08 eV for the divawncy formation enthalpy is obtained.T, This pattern parallels the thermal recovery of the ionic conductivity of~irradialed NaCI. It is suggested that n reflects the annihilation of positrons at cation vacancies thermally released from radialion-induced divacancis. The 72 evolution with the annealing temperature has been analysed in terms of a trapping model and a value of 1.96&0.08 eV for the divawncy formation enthalpy is obtained.that n reflects the annihilation of positrons at cation vacancies thermally released from radialion-induced divacancis. The 72 evolution with the annealing temperature has been analysed in terms of a trapping model and a value of 1.96&0.08 eV for the divawncy formation enthalpy is obtained.72 evolution with the annealing temperature has been analysed in terms of a trapping model and a value of 1.96&0.08 eV for the divawncy formation enthalpy is obtained.