Energy emanating from the molecular nanomagnet Fe₈ revisited

In the molecular nanomagnet Fe$_{8}$ tunneling can occur from a metastable state to an excited state followed by a transition to the ground state. This transition is accompanied by an energy release of $115.6$GHz. We constructed an experimental setup to measure whether this energy is released in the form of thermal or electromagnetic energy. Contrary to a previous publication we find no evidence for release of electromagnetic radiation. Our results for transitions between the first and second excited states to the ground state are consistent with a release of only thermal energy. This energy release extends for a longer time for the second excited state than for the first excited state.