Figure 4.
(a) and (b) Average values of steady-state nuclear spin polarizations (pn,ave, solid symbols) and polarization time constants (tDNP,ave, open symbols) as a function of T1e and MAS frequency from calculations using the 3000-spin level-crossing model with biradical concentrations of 15 mM (circles) and 0 mM (i.e., without intermolecular electron-electron couplings, triangles). The nuclear spin polarization is divided by its thermal equilibrium value pn,therm. (c) Average polarization difference between the two electrons within a biradical as a function of the frequency difference between the electrons, with 15 mM biradical concentration and with T1e equal to 10−6 s (blue), 10−5 s (red), 10−4 s (green), and 10−3 s (aqua). Lines are drawn to guide the eye. Colors in panel (c) correspond to those in panel (a).