| Popis: |
The refractive index of gaseous 14NH3 was measured at distances of -24, -18, -12, -6, +6, +12, +18 and +24 MHz from the (3,3) line of the microwave inversion spectrum. The measurements were performed at pressures of up to 10 mm Hg and at a temperature of 300°K. The measured refraction can be split into two parts: 1) The anomalous dispersion of the (3,3) line with a relatively small additional contribution to the refraction due to all other inversion lines. Using known molecular data the latter contribution was quantitatively calculated on the basis of Van Vleck and Weisskopf's theory on the collision broadening of spectral lines and afterwards subtracted from the measured values in order to obtain the actual refraction of the (3,3) line. The resulting values of the ratio -(n′ − 1)(v − v3,3)p, plotted vesus p|v − v3,3|, are in agreement with the theoretical curve, which reaches a maximum value of 2.03 × 10−3 MHz/mm Hg at zero pressure and decreases by p|v − v3,3| according to a Lorentz curve. The collision broadening constant of the (3,3) line proves to be Λ3,3 = (26 ± 1) MHz/mm Hg at T = 300°K. 2) A part proportional to the pressure caused by transitions in spectral regions of much higher frequency. This part amounts to (n′ − 1) = (3.1 ± ± 0.5) × 10−6p(mm Hg). Rotational transitions theoretically cause (n′ − 1) = = 2.1 × 10−6p(mm Hg) in the microwave and radio-frequency region. Vibrational and electronic transitions are estimated to contribute (n′ − 1) = (0.7 ± 0.2) × 10−6p(mm Hg). |
