| Popis: |
The self- and nitrogen-broadened half-widths and the strengths of three lines in the far i.r. rotational spectrum of water vapor have been measured. These lines are the 21-11 transition at 92 cm-1, the 41-31 transition at 170 cm-1, and the 50-40 transition at 188 cm-1. These are among the very few lines in this region which are sufficiently isolated to be amenable to measurement. The method of equivalent widths, as developed in the Ladenburg-Reiche theory, is used. All measurements are made in a cell of length 21·5 cm. By adding nitrogen at pressures from zero to one atmosphere to water vapor at pressures from 0·5 to 17 mm Hg, these lines may be observed in both the square root and the linear regions of the Ladenburg-Reiche curve. Fitting the data to the asymptotic expansion in the square root region, and to the exact equation in the nearly linear region by a method of successive approximations, the line strengths, self-broadened half-widths, nitrogen-broadened half-widths and relative broadening efficiency is obtained. A new method is introduced to correct for overlap, which is very severe in this region. With the assumption that W/pa, the ratio of the equivalent width to the pressure of the absorber, is constant for the pure water vapor, an equation is obtained for the observed value of this ratio in terms of certain overlap parameters. The resulting line strengths are shown to be in agreement with the calculated values. The self- and nitrogen-broadened half-widths are compared with the calculations made by Benedict and Kaplan on the basis of the Anderson theory. The observed values are larger than the theoretical by a factor of about 1·5. |
