Refractive index of HF from 2.5 microm to 2.9 microm.

The index of refraction of hydrogen fluoride has been measured from 2.5 to 2.9 microm with a wavelength resolution of 40 A. Fringe shifts were measured using an incandescent light, a Mach Zehnder interferometer, and a quarter-meter monochromator. The hydrogen fluoride pressure varied from 20 to 120 T. Higher pressures would not be tolerated because of the presence of HF dimers. From 2.5 to 2.7 microm, the dispersion curve is dominated by the resonant dispersion of the P-branch absorption lines. From 2.8 to 2.9 microm, n - 1 is nearly constant at a value of (1.27 +/- 0.05) x 10(-4) for standard temperature and pressure. Theoretical modeling of the dispersion curve has produced the following values for HF A coefficients: P(l) = 168 +/- 20 sec(-1), P(2) = 120 +/- 20 sec(-1), P(3) = 100 +/- 20 sec(-1).