Table 3.

Comparison of the experimental and simulated B_1e at the sample position

solvent	Irradiated volume (µL)	Cal. $B_{1\mathrm{e}}^{\mathrm{av}}$ (lin. pol.) (mT)	Cal. $B_{1\mathrm{e}}^{\mathrm{av}}$ $\left(\mathrm{circ}.\mathrm{pol}\right).$ (mT)	Experimental $B_{1\mathrm{e}}^{\mathrm{av}}$(circ. pol.) (mT)
CCl4	20	0.033	0.036–0.040	0.045–0.065
H2O	5	0.027		–

Simulated average (av.) B_1e of the sample (CCl₄ and H₂O) (from Supplementary Fig. 3). Values are reported for an input power of 10 W at a frequency of 263.3 GHz. Simulated MW losses at the sample are ~4.2 dB for a 75 mm long wave guide, while experimentally ~6.5 dB were determined (Supplementary Fig. 2). Therefore, for a comparison with the experiment, the simulated $B_{1\mathrm{e}}^{\mathrm{av}}$ of a linearly polarized wave (lin. pol.) was scaled to the same power as used in the experiment $\left(P=40\mathrm{W}\right)$. This was performed by additionally scaling the initial power ratio (40 vs 10 W) by the respective calculated and measured losses in the waveguide (4.2 vs 6.5 dB):

$B_{1\mathrm{e}}^{\mathrm{av}}\left(\mathrm{circ}.\mathrm{pol}.\right)=\frac{1}{\sqrt{2}}\sqrt{\frac{P_{\mathrm{MW}}^{\exp .}\cdot {10}^{-0.65}}{P_{\mathrm{MW}}^{\mathrm{sim}.}\cdot {10}^{-0.42}}}{B}_{1\mathrm{e}}^{\mathrm{av}}\left(\mathrm{lin}.\mathrm{pol}.\right)$.

The factor $1/\sqrt{2}$ accounts for the fraction of linearly polarized field, which is absorbed by the nutating spin.

The obtained experimental and calculated values (last two rows of the Table) are in close agreement. Source data are provided as a Source Data file⁶⁰.