High-temperature photoelectron spectroscopy of the 3d-transition metal dihalides

High-temperature He(I) photoelectron spectra of the vapors over a heated mixture of a metal powder and AgX (X = Cl, Br) and of the vapor species (AgCl)₃ and (AgBr)₃ have been obtained. The vapor has been determined to be predominantly MX ₂ (M = Cr, Mn, Fe, Co, Ni) or (CuX) ₃ (X = Cl, Br) except over the Ni powder-AgBr mixture where the vapor contains a significant AgBr component. The spectra of (AgCl) ₃, (CuCl) ₃, and (CuBr) ₃ are similar to published spectra. The (AgBr) ₃ spectrum is and 10.77 eV assigned to halogen ionizations and three peaks at 12.59, 13.54, and 14.06 eV thought to arise from Ag 4d orbitals.

Spin-restricted overlapping spheres multiple scattering Xa calculations have been performed on several electronic configurations of TiX ₂, VX ₂ , CrX ₂ , MnX ₂, FeX ₂ CoX ₂ , NiX ₂, and ZnX ₂ (X=Cl, Br) Configurations include both high-spin and low-spin occupancy in all molecules plus δ³&pi²&sigma⁰ MnX₂ and δ³&pi³&sigma¹ CoX_{2(X = Cl, Br). Agreement with experiment, where available, is satisfactory. Analogous spin polarized calculations have been performed on the same electronic configurations of CrCl 2, MnCl 2, FeCl 2, CoCl 2, and NiCl 2 with less satisfactory agreement with experiment. The lowest ionization energy peaks at 9.92 eV from CrCl 2 , 9.32 eV from CrBr 2 , 10.92 eV from MnCl 2 , 10.37 eV from MnBr 2 , and 11.37 eV from NiCl 2 are assigned as arising from metal 3d orbitals. The two lowest energy ionization peaks at}

eV (intensity ratio 1.0:2.6) from FeCl _{2, 9.68 and 10.35 eV (intesnisty ratio 1.0:2.6) from FeBr 2, 10.71 and 11.48 eV (intensity ratio 1.0:2.8) from CoCl 2 , and 9.88 and 10.46 eV (intesity ratio 1.0:1.2) from CoBr 2 are thought to arise form metal 3d orbitals. A broad band appears in the region ~l2-14 eV in the dichlorides and ~11-13 eV in the dibromides thought to arise primarily from halogen orbitals. The number of d-electron peaks and their intensities are discussed and appear consistent with the peaks grouping by spin multiplicity of final ion states produced upon d-electron ejection. Vapor-phase ground state configurations appear to be δ⁴π²σ⁰ in FeCl 2 and FeBr 2 , δ³π³σ¹ in CoCl2, δπ³σ⁰ in CoBr2, and δπ⁴σ⁰ in NiCl2 and NiBr2. Results seem to favor no particular ground state configuration in CrX2, or MnX 2 (X = Cl, Br).}