Published online by Cambridge University Press: 28 February 2011
The N1 centre in Type Ia diamonds is a di-nitrogen centre with S = ½. One nitrogen's interaction with the unpaired electron at room temperature gives a large splitting, All = 46.4 G, A ⊥ = 32.2 G with <111> symmetry while the hyperfine splitting due to the other one has <110> symmetry with parameters All = 2.95 ±.03 G, A⊥ = 2.81 ±.03 G. As the temperature is increased averaging effects start; first some hyperfine lines broaden at about 150°C and disappear at 200°C. At still higher temperatures new lines appear and at about 850°C the averaging process is completed. The interpretation of the dynamics leads to a model of a non-planar N-C-C-N configuration with the electron jumping between the two N-C bonds. The measured activation energy is 0.4 eV which is about midway between the measured values for a similar effect in the isolated nitrogen centre, P1, (E = 0.7eV) and the N-C-N, W7, centre (E = 0.24 eV).