Figure 4.

2D frequency versus resonance field plot for compound 4 at 10 K. The circles denote experimental data points, and the curves are fits to an effective spin S = 1 Hamiltonian [eq 1] with the parameters given in the main text. Colors denote different components (x, y and z; see legend) of the powder spectra; the solid curves indicate cold transitions (assuming D > 0) originating from the ground state of the S = 1 manifold and, therefore, persist to the lowest temperatures. The dashed curves indicate transitions within excited states of the S = 1 manifold.