Knowledge Bank

The infrared absorption of hydrogen fluoride vapor in the 3-micron wavelength region has been measured as a function of pressure and temperature between $-70\circ$ and $+100\circ C$. This absorption can be interpreted entirely on the basis of two overlapping bands. The absorption of one band varies as the fourth power of the pressure as would be expected for a tetramer, $(HF)4$, in low concentration. This band predominates at the lower pressures and higher temperatures. The absorption of the other band varies as the sixth power of the pressure as would be expected for a hexamer; $(HF)6$, in low concentration. No evidence has been found to indicate absorption by any other polymer. The tetramer band appears to have three broad maxima at 3500, 3380, and about 3080 Kaysers. The hexamer band has but a single maximum at 3380 Kaysers. These bands are very broad. The first overtone bands are nearly twice as broad as the fundamental bands, indicating a wide distribution of force constants. Attempts have been made to evaluate the heats of polymerization, and the monomer polymer equilibrium constants. Preliminary investigations of the longer wavelength region have also been made. Here the absorption can be interpreted on the basis of broad overlapping bands which show the same fourth- and sixth-power pressure variations. There is a maximum absorption attributed to the tetramer at 709 Kaysers. There are two maxima attributed to the hexamer at 1175 and 775 Kaysers.