The research within the MuSES project - photoexcited muon spectroscopy - is breaking new ground and is quite challenging. It is important to establish the technique methodology first by performing a study in a prototype system, which is relatively simple and therefore easy to perform quantum-chemical calculations of electronic states. In general the lifetime of the fluorescence is in the order of 10 ns, which is too short to measure the interaction of the muonium (Mu) radical with the excitation on the molecule. Therefore it is ideal to use a fluorophore with long fluorescence lifetime with the simple molecular structure. One of the candidates is pyrene, whose lifetime is 450 ns in cyclohexane at room temperature, leaving a plenty of time for the Mu to interact with the local field as well as a sufficiently long timescale to allow it to be measured.