5f covalency in Americium hexachloride
The Cl K-edge XAS of Americium(III) Hexachloride were simulated and analyzed based on spin-orbit DFT transition dipole moment method. Direct evidence of 5f and 3p orbital mixing in Am–Cl bond was observed. Combining experimental Cl K-edge XAS and theoretical simulation, the comparison between AmCl63- and isoelectronic EuCl63- confirms Seaborg’s 1954 hypothesis that AmIII 5f-orbital covalency was more substantial than 4f-orbital mixing for EuIII.
Left: The experimental data (•) and the curve fitted model (blue trace) for the Cl K-edge XAS spectrum from (PPh4)3AmCl6 and (PPh4)3EuCl6. Comparison between the experimental Cl K-edge XAS spectrum (•) and orbital-difference DFT calculations (black trace). The orange, green, purple, and grey bars and dashed traces represent the energy and oscillator strength for the calculated transitions involving 5f- and 6d-final states. Right: t1u orbital in AmCl63- (HOMO) showing involvement of both Cl and Am 5f-orbitals.
