Spontaneous Annihilation Research Articles

Resistometric measurements on molybdenum irradiated with 2.5 MeV electrons

The production and recovery of damage in molybdenum produced by irradiation with 2.5 MeV electrons at ~50°C was studied by observation of the change in electrical resistivity. All damage produced recovered completely in one stage around 195° C and is associated with an activation energy of 1.29 ± 0.04 eV. The initial recovery of the isothermal annealing is proportional with √ t whereas the tail end obeys second-order kinetics. The results are consistent with a model in which the recovery is ascribed to the random migration of interstitials to vacancies leading to their mutual annihilation, whereby the initial recovery involves predominantly the annihilation of interstitials with the vacancy from which they are originally dislodged as theoretically described by Waite. The diffusion constant for the interstitial molybdenum atom is: D/ a 2 = 0.9 × 10 12 ± 1exp {(−1.29 ± 0.04)/ kT} and the capture radius r 0 for the spontaneous annihilation of interstitials with vacancies: 15 A ̊ < r 0 < 36 A ̊ . Independent evidence for this large capture radius is obtained from the production rate curve; saturation is observed at large doses giving a maximum concentration of Frenkel pairs of ~ 8 × 10 −5.