The electronic structures of crystalline and aqueous solutions of LiBr, NaBr, KBr, and KBrO3 were studied using in-situ Br L-edge near-edge X-ray absorption fine structure (NEXAFS) under ambient conditions. The direct observation of the ligand-field potential (10Dq) allows the determination of their dependence on the interatomic distances between Br and the first near neighbor in crystalline LiBr, NaBr, KBr, and KBrO3 and the effect of hydration in the corresponding aqueous solutions. DV-Xa molecular-orbital calculations show that for both crystalline and aqueous solutions of KBr, the transitions occur from Br 2p to the unoccupied states containing mainly 4d orbitals of Br. The 5s and 5p orbitals of Br and 3d orbitals of K also contribute to the unoccupied states in addition to the 4d orbitals of neighbor Br due to the orbital mixing in crystalline KBr
