Fig. 5: Outlook for the application of the ENDOR qdyne detection scheme.
From: High-resolution nanoscale NMR for arbitrary magnetic fields
a Schematic of the extension of the sensing scheme to sample detection. Only the target spins with sufficient Azz coupling (red spins) will be detected by our measurement scheme. b Relation between implantation depth of the NV centers and the detected linewidth. By increasing the depth of the NV centers, the dipolar coupling via Azz decreases, resulting in a decreasing linewidth of the ENDOR qdyne protocol (see Eq. (3)). For example, a linewidth of 1 Hz is predicted at dNV = 4.2 nm for 1H target spins (grey line). However, as the Azz coupling decreases, the number of detected target spins has to increase to maintain sufficient signal quality. The orange lines represent the necessary number of detected 1H target spins to reach a SNR of 3 in a 10 min measurement cycle with 100 points. For the case of dNV = 4.2 nm104 target spins in the detection volume are sufficient if a NV ensemble of 1000 sensor spins is used. This can easily be achieved, as the dashed orange line shows the number of 1H target spins of a water sample in the detection volume of the sensor when thermal polarization in a 3 T bias field is considered.
