This thesis is about the tunneling dynamics of the Fe₈ molecule in the presence of an environment. Although a lot of progress has been made experimentally to determine among many things the extremely small tunnel splitting energies of this macromolecule, the question of how the environment affects the molecule has still not been properly understood.

It is the purpose of this thesis to put forward a coherent model for the decoherence processes that affect the Fe₈ molecule. The decoherence allows us to treat the Fe₈ molecules as classical objects and we can write down rate equations that determine the relaxation dynamics of the entire Fe₈ solid. The theoretical predictions are in very good agreement with Monte-Carlo simulations of spherical samples.

We believe that the model developed can be generalized to different geometries and also improvised to tackle the different experimental protocols that have been undertaken on these macroscopic molecules.