Vibrational spectra of polycrystallineMNCO (M = K,Rb, Cs)

IR and Raman spectra are reported for polycrystalline samples of the isomorphousMNCO (M=K,Rb,Cs). The lattice modes are generally assignable to the symmetry species of the factor groupD_4h by analogy with those ofMN₃, but the internal modes are not, in general, interpretable by any known practical analysis. These spectral features may be associated with the disorder of the NCO^– ions in the crystal structure.