Raman, resonance-Raman, and electronic spectra of tetraethylammonium hexabromoantimonate(V) and of tetra-n-butylammonium hexa-bromoantimonate(V)

Abstract

The resonance-Raman (r.r.) spectrum of the [SbBr₆]^– ion, as the tetraethylammonium salt, is dominated by a high-intensity overtone progression in the ν₁(a_1g) fundamental (191.5 cm^–1) extending as far as 9ν₁. Three other progressions have also been observed, in each of which ν₁ is the progression-forming mode, viz. ν₂(e_g)+v₁ν₁(to v₁= 5), ν₅(t_2g)+v₁ν₁( to v₁= 1), and ν_L+v₁ν₁(to v₁= 3, ν_L being a lattice mode at 49 cm^–1). The fifth observed progression in the r.r. spectrum of this ion involves the ν₂(e_g) fundamental (169 cm^–1) as the progression-forming mode, to v₂= 4. Calculated harmonic frequencies ω₁, and ω₂ are 191.6 and 169.5 cm^–1 respectively, and anharmonicity constants x₁₁, x₂₂, and x₁₂ are –0.05, –0.14, and 0.15 cm^–1 respectively. The resonant electronic transition (maximum at 21 500 cm^–1) is concluded to be the electric-dipole allowed transition a_1g(σ*)â†�t_1u(π), ¹T_1uâ†�¹A_1g, in O_h nomenclature.