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Strongly correlated electron systems continue to shed new light on the fundamental interactions of electrons in solids. With hallmark behaviors like metal-to-insulator transitions and high temperature superconductivity, Mott insulating transition metal oxides are a canonical example of strong electron-electron correlations. Here we investigate epitaxial heterostructures of the Mott insulating rare earth titanate SmTiO 3 (SmTO) embedded with quantum wells of the band insulator SrTiO 3 (STO). This system exhibits both quantum critical transport and pseudogap behavior suggesting strong parallels with bulk Mott materials. In this work, we use resonant X-ray reflectometry at the Ti L-edge to probe the orbital polarization depth profiles of a SmTO film and SmTO-STO superlattices with varying STO quantum well thickness. Our results suggest that the d 1 electron in SmTO preferentially occupies the in-plane d xy orbital …