Vibrational Spectra and Thermodynamics of the Zinc Halides

The infrared absorption spectra of the four zinc halides have been investigated by the low-temperature matrix-isolation technique. The spectral range 800–35 cm−1 has been covered. Four absorption regions have been observed in all cases. The highest energy region is structured and represents the antisymmetric stretching frequency ν3. The structure has been fully characterized as due to molecules of different isotopic compositions. The second and third absorption regions have been demonstrated to be due to higher polymers by means of double-oven experiments. The lowest-frequency absorption has been assigned as the bending vibration ν2. Statistical calculations of the molecular entropies have been carried out on the basis of the new results, and these entropy values are found to be in excellent agreement with third-law entropy values where available.