A Dynamic Jahn-Teller Effect in the ESR Spectrum of the N1 Centre in Diamond

Abstract

The NI centre in Type Ia diamonds is a di-nitrogen centre with S = One nitrogen's interaction with the unpaired electron at room temperature gives a large splitting, All = 46.4 G, Al = 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; fiFst some hyperfine lines broaden at about 1500C and disappear at 200'C. At still higher temperatures new lines appear and at about 8501C 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).

Long coherence times at 300 K for nitrogen-vacancy center spins in diamond grown by chemical vapor deposition

“…with gϭ2.0028 and Dϭ960ϫ10 Ϫ4 cm Ϫ1 with the z axis along a ͗111͘ direction. 5 The electron paramagnetic resonance ͑EPR͒ or optically detected magnetic resonance line for the NV Ϫ center in a high-purity diamond is inhomogeneously broadened by magnetic interactions with other spins through dipolar interactions and electric interactions with other charges through the D term in the Hamiltonian. The static effects lead to dephasing over the ensemble of spins.…”

EPR studies on the di-nitrogen centers with nonequivalent atoms in a reddish-brown plastically deformed diamond

“…We have selected for analysis those symmetryrelated sites of the W7 and M2 centers for which the direction of the principal axis of A~ coincides with the [111] axis. The direction of the principal axis of A 2 for all currently known centers on two nonequivalent nitrogen atoms does not coincide with any special direction in the diamond structure, it appears close to one of the (111) axes, but not to the principal axis of A v In earlier investigations, this fact gave a basis to assign the model NI..c..N2+ to the NI and W7 centers [5,7]. A similar relationship between the orientations of the principal axes of A~ and A 2 is observed for center M2.…”

“…Centers with two nitrogen atoms ate of special concem because the observed hyperfine structure allows one to establish a positional relationship of nitrogen atoms and to constrain, thus, a model for the center. Such centers as NI [3][4][5], N4 [6], W7 [7], and W24 [8] have been found in various crystals of plastically deformed natural diamonds. The electron paramagnetic resonance (EPR) parameters of these centers were repeatedly updated, and electronnuclear double resonance (ENDOR) measurements [9,10] have supplemented them also by quadrupole characteristics.…”

Raman heterodyne detected electron-nuclear-double-resonance measurements of the nitrogen-vacancy center in diamond

“…Uniaxial stress measurements with the zero-phonon line have shown that it is associated with an A-E transition at a site of trigonal symmetry. 5 There is also an associated EPR signal from a spin triplet, 6 which has been shown to be associated with the ground state. 7 The spin Hamiltonian for a 3 A ground is H = fHgS + SDS + SM -AHg 1 I + IPI.…”

“…EPR measurements give a value of g = 2.0028 and a magnitude of the crystal field splitting of the triplet IDI = 2.88 GHz. 6 The hyperfine structure is associated with nitrogen, the only atom in the center with a nonzero nuclear spin, resulting in an EPR spectrum consisting of three lines separated by A = -2.3 MHz. The nuclear Zeeman splitting of nitrogen is known to be ,ugj = 3 MHz/ T. However, EPR is not sensitive to terms that depend only on nuclear spin, and consequently the value of the quadrupole interaction parameter P in the last term in Eq.…”