Raman spectrum of rubidium iodide

Raman spectrum of rubidium iodide has been recorded for the first time using the resonance radiation of mercury (λ 2537 Å) as the exciter. The frequencies of the 24 p limiting modes ( p = 2, the number of non-equivalent atoms in the unit cell), postulated by Raman in 1943, which correspond to the frequencies from the critical points Γ, L and X, have been worked out using the shell model of Cochran, taking into account the nearest and the next-nearest neighbour short-range interactions and the polarization of both the ions. The observed Raman lines have been assigned to the overtones and the combinations of the phonon branches from Γ, L and X.