Abstract
Polarized ir absorption spectra of CsNO3‐II and RbNO3‐IV crystals have been investigated in the region of the fundamental vibrations of the nitrate ions at 80 and 300 °K as well as the Raman spectra of these crystals at room temperature. Apart from the local field effects and the Davydov splitting of some vibrational terms also a splitting due to the presence of several sets of molecules not related by symmetry in a unit cell was observed. These results agree with the more accurate data of X‐ray analysis of the crystal structure of the low‐temperature phases of cesium and rubidium nitrate.