Influence of intermolecular resonance of fundamental oscillations on the fine structure of luminescence spectra of uranyl compounds

A previous investigation of the contours of fluorescence spectrum lines of uranyl crystals of an island structure has shown that the broadening of optical transitions on energy sublevels of stretching fully symmetrical vibrations of UO2+2 may be explained by the intermolecular resonance (IR) of ν1(UO2+2) vibrations of nearby luminescence centers. A successive increase of the vibrational quantum number n of this vibration is appropriate for the gradual isolation of a low-frequency diffuse wing (presumably of a background nature) and the narrowing of the lines. At the same time the Raman scattering (RS) line is narrower by more than one order than the appropriate fluorescence line (FL) even with deduction of the quantity of inhomogeneous broadening of the latter. In this connection, of interest is a comparison of the FL width and location in the crystals of uranyl compounds and in the UO2+2-activated suitable crystalline matrix where IR is, in fact, absent