Temperature Sensitivity of 14 N- V and 15 N- V Ground-State Manifolds.

We measure electron- and nuclear-spin transition frequencies in the ground state of nitrogen-vacancy (N- V ) centers in diamond for two nitrogen isotopes (14 N- V and 15 N- V ) over temperatures ranging from 77 to 400 K. Measurements are performed using Ramsey interferometry and direct optical readout of the nuclear and electron spins. We extract coupling parameters Q (for 14 N- V ), D , A ‖ , A ⊥ , and γe/γn, and their temperature dependences for both isotopes. The temperature dependences of the nuclear-spin transitions within the ms=0 spin manifold near room temperature are found to be 0.52(1) ppm/K for 14 N- V (| mI = -1⟩ ↔ | mI = +1⟩) and -1.1(1) ppm/K for 15 N- V (| mI = -1/2⟩ ↔ | mI = +1/2⟩). An isotopic shift in the zero-field splitting parameter D between 14 N- V and 15 N- V is measured to be ~ 120 kHz. Residual transverse magnetic fields are observed to shift the nuclear-spin transition frequencies, especially for 15 N- V . We have precisely determined the set of parameters relevant for the development of nuclear-spin-based diamond quantum sensors with greatly reduced sensitivity to environmental factors.