We request 5 days on EMU to study the NH4+ ion mobility in the light borohydride materials NH3BH3, NH4BH4 and CH3NH3BH4. As has been proposed by Stowe et al., during the dehydrogenation of NH3NH3 there forms a "mobile" phase, identified by 11B NMR spectroscopy as the diammoniate of diborane. This phase is the crucial intermediate for the dehydrogenation of NH3BH3 and also forms in situ during the dehydrogenation of NH4BH4. Muon spin relaxation spectroscopy on EMU will allow us to study the muon hopping mechanism in these sample as a function of temperature. These information will help us to understand the nature of the "mobile" phase and will provide evidence for the proposed dehydrogenation mechanism.