Silicon is currently the base of all modern electronics and advanced computing. One route to future advanced computing called spintronics exploits the energy saving and quantum information encoding possible in the spin, rather than the charge of the electron. Silicon spintronics research has been impeded by the generally accepted absence of a means to optically inject spin-polarized electrons due to its indirect bandgap. We recently observed it is possible to inject spin-polarized electrons and detect these spin-polarized electrons using the difference in how they interact with spin-polarized muons. In the proposed research we hope to understand the detailed microscopic mechanism for the muon sensitivity to spin-polarized electrons and to quantify what fraction of optically-injected electrons are spin-polarized. The larger the fraction the more impact it will have on Silicon spintronics.