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

Abstract

Two new di-nitrogen centers, which were labeled M2 and M3, were found together with known W7 and N4 centers in an unusual reddish-brown natural diamond. The following magnetic hyperfine interaction parameters (expressed in MHz) were determined for the two nitrogen atoms:A ⁽¹⁾₁ =117.95(5),A ⁽²⁾₁ =A ⁽³⁾₁ =84.48(5),A ⁽¹⁾₂ =7.1(1),A ⁽²⁾₂ =A ⁽³⁾₂ =6.6(1) for M2 andA ⁽¹⁾₁ =121.55(5),A ⁽²⁾₁ =A ⁽³⁾₁ =85.90(5),A ⁽¹⁾₂ =6.0(1),A ⁽²⁾₂ =5.4(1),A ⁽³⁾₂ =5.1(1) for M3. Hyperfine interaction tensors for the nitrogen atom N₁ with a larger interaction have axial symmetry about the <111> direction, but those for the other nitrogen atom, N₂, appear to be small, almost isotropic. Probable models of the M2 and M3 centers are suggested and discussed.