Knowledge Bank

The intensities and shapes of the lines in the fundamental band of hydrogen fluoride have been studied at $117\circ C$. and pressures ranging from 200 to 3860 mm Hg. Slit corrections, performed with the aid of an IBM calculating machine, amounted to less than 3% in the absorption coefficient at 3860 mm Hg for the lines R(5) to P(7) and went as high as 25% on even the strong lines at 700 mm Hg. The lines were found to be symmetrical about the line center. A shift in the line center of the order of tenths of a wave number at 3860 mm Hg was observed. The line breadths vary with J from 0.5 to less than $0.2cm-1$/atmosphere. A study of the line intensity gives |{d}\mu{d}{r}|=1.6\times 10^{-10}\mbox{c.s.u.} with the dipole moment increasing with increase in r. In the wings of the lines where no slit corrections are required the absorption coefficient was found to be quadratic in the pressure and always appreciably higher than calculated for a Lorentz line of the same height and breadth. At the center of the R(2) line the absorption coefficient was observed to decrease 11% with increase in pressure from 700 to 3860 mm Hg. A decrease of 3% was observed between 2310 and 3860 mm Hg, in which pressure range the maximum slit correction was 3%. Polymer absorption peak was found adjacent to the band center, on the high wave number side.