Knowledge Bank

The infrared spectra of thin films of the hexafluorides of sulfur, selenium, tellurium, molybdenum, tungsten, and uranium have been observed from 2 to 15$\mu$. For $UF6$, the observations were extended to 18$\mu$ in order to observe $\sigma 3$. The films were deposited on a silver chloride plate chilled by heat conduction through a hollow silver mounting bracket containing liquid nitrogen. $\sigma 3$ was found to fall at longer wavelengths in the solid state than in the gas state for all six molecules. $\sigma 1+\sigma 3$ and $\sigma 2+\sigma 3$ were observed doubled in the solid state in each case.