Echo-detected field-swept spectra (EDFS) of 1-Nd, 1-Ce and 1-Sm (in toluene-hexane) are observed up to 10 K (see Supplementary Information for all pulsed EPR spectra). These were recorded by integration of the Hahn echo generated with the standard pulse sequence π/2 -τ -π -echo, where π/2 and π are microwave pulses and τ is the inter-pulse delay. The EDFS spectra at 5 K for 1-Nd, 1-Ce and 1-Sm (Figures and) are consistent with the CW spectra, Qband EDFS are consistent with the rhombic g-values of 1-Nd and 1-Ce (Figure ). Measurements of the spin-lattice (T1) and phasememory (Tm) relaxation times were performed at Xband on 10 mM frozen solution samples of 1-Nd, 1-Ce and 1-Sm at 5 K. T1 data were recorded with an inversion recovery pulse sequence, and the data fitted with a bi-exponential function (see Supporting Information Eqn 3; Figures and), where the fastest process is assigned to the spectral diffusion and the slow process is attributed to the spin-lattice relaxation. The T1 value for 1-Nd is field-dependent and reaches a maximum value of 12 μs at the highest field g-value (12360 G, Table ). Measured at the maxiumum of the EDFS (6040 G), T1 is 5 μs. Much longer maximum T1 times of 89 and 150 μs were obtained for 1-Ce (at the high-field g-value, 11228 G) and 1-Sm (at the low-field g-value, 6936 G), respectively (Tables and). For comparison, T1 measured at the EDFS maxima are 78 and 118 μs for 1-Ce and 1-Sm, respectively.