Single-chain magnets are an interesting, novel class of molecular nanomagnetic materials. In order to understand the relaxation of the magnetization in these materials, it is essential to understand the lowest energy excitations. These were predicted to be either excitations localized on one of the units composing the chain, or collective excitations delocalized over the chain (spin waves). We have studied the single chain magnet abbreviated as Mn2Ni by by means of broadband high-frequency electron paramagnetic resonance. We observe a zero-field transition at ca. 331 GHz (1.37 meV) and a further, weaker transition. For a local excitation, one would expect the ground state transition at 5D, and excited state transitions at 3D and D, where D is the second rank axial zero-field splitting. However, no excited state transitions were observed. Inelastic neutron scattering is the ideal technique to resolve this issue, leading to an improved understanding of the relaxation of magnetization in Mn2Ni and in single-chain magnets in general. Excitation energies up to 1.4 meV are involved.