The electronic structure and electron momentum density distribution in BaO and BaS are presented using Compton spectroscopy. The first-ever Compton profile measurements on polycrystalline BaO and BaS were performed using 59.54？keV gamma-rays. To interpret the experimental data, we have computed the theoretical Compton profiles of BaO and BaS using the linear combination of atomic orbitals method. In the present computation, the correlation scheme proposed by Perdew-Burke-Ernzerhof and the exchange scheme of Becke were considered. The hybrid B3PW and Hartree-Fock based profiles were also computed for both compounds. The ionic configurations are performed to estimate the charge transfer on compound formation, and the present study suggests charge transfer from Ba to O and S atoms. On the basis of equal-valence-electron-density profiles, it is found that BaO is more ionic as compared to BaS. 1. Introduction The II–VI alkaline earth compounds have interesting bond characteristics and simple crystal structures. BaO and BaS have potential applications in light-emitting diodes (LEDs), laser diodes (LDs), and magnetooptical devices [1–4]. BaO is an indirect bandgap, whereas BaS is a direct bandgap material. At normal conditions, BaO and BaS crystallize in NaCl (B1) structure, but under pressure, they show structural phase transition from B1 to B2 structure [5, 6]. Using the full-potential linearized augmented plane wave (FP-LAPW) method, Drablia et al. [7] reported the electronic and optical properties of BaO and BaS in cubic phase at normal and under hydrostatic pressure. Lin et al. [8] observed that the electronic structure of these compounds containing oxygen atoms always obeys a different relationship from the compounds not containing oxygen atoms using density functional theory (DFT). Most of the earlier studies, both experimental and theoretical, involve the electronic, optical, and structural properties of BaO and BaS [5–15]. To the best of our knowledge, no one attempted the electronic structure and momentum density of BaO and BaS using Compton spectroscopy. It is well established that Compton spectroscopy provides a useful test to examine the bonding in solids [16, 17]. Thus, we found it worth to study the electronic structure in BaO and BaS using Compton profile. The Compton profile, , is related to the ground state electron momentum density as [16, 17] where integration is performed over a constant- plane, is scattering vector direction, and is given as where is the electron wave function and summation extends over all occupied states. In this paper,
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