Resonance Raman and electronic spectra of different salts of the [AuBr4]– ion
Abstract
Three different salts of the [AuBr4]– ion display the resonance Raman effect when irradiated in the solid state with any one of several different exciting lines (frequency νo). For 457·9 nm excitation, which approximately coincides in frequency with that of an intense electronic band maximum (νe) of the anion, the resonance is most effective, with high-intensity overtone progressions in the ν1(a1g) fundamental extending as far as the ninth harmonic. For each salt, two other progressions in the ν1(a1g) fundamental have also been observed, viz. ν2+nν1 and ν4+nν1, where ν2(b1g) is an AuBr stretching fundamental, and ν4(b2g) is a BrAuBr bending fundamental. The members of each overtone progression decrease in intensity and increase in half-bandwidth with increase in the vibrational quantum number. The relationship between the overtone intensities and νe–νo is detailed. The observation of various overtone progressions has permitted the determination of the spectroscopic constants ω1 and x11 for the [AuBr4]– ion in each crystalline environment.