where C is a constant of dipolar interaction, 𝜏 𝑐 is the correlation time of the dipolar interaction, and ω is the resonance frequency. The spin-spin relaxation time is given by 5 : The T1, δ measurements at 133 kHz were carried out to understand the field dependence of T1 relaxation, since the difference between 233 MHz and 291 MHz was not significant. However, in the range of temperatures available on the VNS 750 solid-state probe, T1,δ is T2-limited, and therefore, we cannot make conclusions on the field dependence on T1 based on our rotational frame of reference T1, δ measurements.