High-resolution photoabsorption and photoelectron spectra of bromine-containing molecules at the Br 3d edge: the importance of ligand field splitting

Abstract

Using monochromatic synchrotron radiation, we have recorded high-resolution Br 3d photoelectron and photoabsorption spectra (PES and PAS, respectively) for the five molecules: HBr, DBr, and . The Br 3d PES of HBr, DBr and show five peaks due to the combined effects of ligand field (or molecular field) and spin - orbit splitting. The and PES are vibrationally broadened, but also show additional broadening from ligand field splitting. The Br 3d ligand field splittings (as quantified by the crystal field parameter) are similar to the I 4d values for the iodine analogues, and increase in the order of . The Br 3d binding energies also increase in the above order due to the increasing electronegativity of the substituents. The very complex Br 3d photoabsorption spectra also show the same ligand field/spin - orbit splitting which split each transition into five transitions. These spectra are dominated by the peaks from the five transitions; but a myriad of other peaks from the (n = 4, 5), np (n = 6 - 9), ns (n = 6, 7) and nf (n = 4, 5) transitions are required to fit these spectra. Good fits to all the spectra have been obtained using ligand field splittings which are similar to the PES results, and quantum defects for s, p, d and f orbitals of , 1.6 - 2.0 and 0.8 - 1, respectively.