  We report a systematic investigation on the spectral splitting of negatively
charged, nitrogen-vacancy (NV-) photo-luminescent emission in single crystal
diamond induced by strain engineering. The stress fields arise from MeV
ion-induced conversion of diamond to amorphous and graphitic material in
regions proximal to the centers of interest. In low-nitrogen sectors of a HPHT
diamond, clearly distinguishable spectral components in the NV- emission
develop over a range of 4.8 THz corresponding to distinct alignment of
sub-ensembles which were mapped with micron spatial resolution. This method
provides opportunities for the creation and selection of aligned NV- centers
for ensemble quantum information protocols.
