High-temperature photoelectron spectroscopy of alkali nitrate, metaphosphate, and cyanide vapors

The high-temperature He(I) photoelectron spectra of the gas-phase molecules KNO₃, RbNO₃, CsNO₃, NaPO₃, KPO₃, RbPO₃, CsPO₃, NaCN, and KCN have been obtained. The vapors were produced by resistance heating a tantalum-strip-wound quartz sample oven which was coated with a hightemperature ceramic cement. Analysis of the ejected electrons was carried out using a modified truncated cylindrical-mirror electron spectrometer. Assurances regarding the identities of the vapor-phase species were had by using data obtained from the techniques of electron diffraction, mass spectrometry, microwave spectroscopy, and matrix-isolation and vapor infrared spectroscopies. The ionization energies were assigned molecular orbital origins through the use of molecular orbital calculations, comparisons with X-ray, He(I), and He(II) photoelectron data for the solids, and analogies with other compounds of similar type.

Observations concerning the similarities of the spectra of all compounds containing the same anion and concerning the correlation of the experimental data with theoretical calculations for the corresponding free anions led to the possibility that a high-temperature structural model cailed polytopic bonding might be applicable to these vapor species. The observed spectral band breadths, however, were considerably greater than the splits expected on the basis of theoretical calculations for various structural parameter changes. It was, therefore, concluded that no judgment could be made concerning the possible polytopicity of these compounds at high temperatures.