HF LINE $FREQUENCIES^{*}$

Author Institution: K-25 Technical Division, Carbide and Carbon Chemicals Company; Physics Department, The University of TennesseeThe pure rotational spectrum of monomeric hydrogen fluoride has been observed in the region 16-23 $\mu$ both in absorption and emission. The sample cell used for all measurements was of Monel closed with silver chloride windows, filled to one-half to one atmosphere pressure, and was heated up to $320^\circ C$ to observe the lines $J = 10 - 15$ inclusive. Wave numbers of the lines observed were $J = 10, 441.21 cm^{-1}; J = 11, 479.00 cm^{-1}; J = 12, 516.27 cm^{-1}; J = 14, 588.90 cm^{-1}; J = 15, 624.13 cm^{-1}$. The rotational constant $B_{o} = {h}/8\pi^{2}{cI}_{o} = 20.546$ cm$^{-1}$, and the centrifugal stretching constant $D_{o}= 0.002035 cm^{-1}$ as compared with 20.555 cm$^{-1}$ and 0.0022 cm$^{-1}$ given previously by Talley, Kaylor and $Nielsen.^{1}$ These earlier measurements on the fundamental vibration-rotation band of HF were limited to lines of low J values because of the use of fluorothene windows and because of polymer absorption at high pressure. At $100^\circ C$ $CaF_{2}$ windows are not etched as they are at lower temperature and no polymer is persent. Higher J lines up to R(11) and P(11) were measured and the first overtone lines remeasured, permitting a more accurate evaluation of the molecular constants.[FIGURE] With these values for the constants the calculated line frequencies agree with the experimental values within $\pm 0.2 cm^{-1}$