The transition at 1062 cm -1 may be attributed to a transition to the second sextet of the ground state spin ladder. From this, however, a value of only J = 288 cm -1 would follow, which is in conflict with the value indicated by the position of the lowest quartet (see discussion above) and with the measured susceptibility. This likely points to the limits of the simple spin Hamiltonian models for the higher lying states, where couplings to further states may become important. In summary, the observed FIR and Raman transitions allow us to conclude that the spin-orbit coupling at the Co centers is essentially the same as in the mononuclear compound and that the exchange coupling strength is of the order of 390 cm -1 . Additional higher-lying signals are transitions to excited sextet states and point to the presence of additional spin-ladders due to low-lying excited electron configurations at the Co centers.