Fig. 6.

Intrinsic linewidth of Gd³⁺ chelates. The cw EPR spectra compare the central transition of Gd³⁺ at 1 mM (r̄ = 6.6 nm) in three different coordinating environments. Gd595 is plotted as a dotted blue line, and shows a linewidth slightly narrower than freely dissolved GdCl₃ (dashed green line), where the Gd³⁺ is coordinated by the solvent. 4MMDPA, plotted as a solid red line, shows a linewidth nearly twice as broad as the others.