To avoid overparameterization, the QTM was set to zero (and is therefore not included in Equation ) and this assumption is validated by the dependence of the QTM rate to H -2 (where H is the magnetic field), which causes suppression of this relaxation phenomenon under an applied field. For the same reason, we chose to fix the energy barrier to the theoretically expected value of 2D using the experimentally obtained D (224 K (156 cm -1 ), 170 K (118 cm -1 ) and 273 K (190 cm -1 ) for [Co(1-3)](ClO4)2, respectively; all parameters obtained from the fitting are summarized in Table ). We note that for such large zero-field splittings, the D-values derived from dc magnetic measurements are quite reliable. This resulted in reasonable fits of the data, with a minimal contribution from the Orbach process (see Figure ). The direct process was considered in the fitting, due to the dependence of the direct coupling between the |+3/2> and |-3/2> states to H 4 . The exponent of the Raman mechanism n was set here as fit parameter and values in the range from 2.9 -4.0 were obtained: even though n = 9 is predicted for Kramers doublets in extended lattices whose dynamics are well described by the Debye model, much lower values have been reported for molecular compounds due to the importance of optical phonons (essentially molecular vibrations) to the relaxation process. Furthermore, fixing n = 9 did not lead to satisfactory fits of the data. for fitting parameters.