  Nitrogen-vacancy (NV-) color centers in diamond were created by implantation
of 7 keV 15N (I = 1/2) ions into type IIa diamond. Optically detected magnetic
resonance was employed to measure the hyperfine coupling of the NV- centers.
The hyperfine spectrum from 15NV- arising from implanted 15N can be
distinguished from 14NV- centers created by native 14N (I = 1) sites. Analysis
indicates 1 in 40 implanted 15N atoms give rise to an optically observable
15NV- center. This report ultimately demonstrates a mechanism by which the
yield of NV- center formation by nitrogen implantation can be measured.
