DISPERSION THROUGH THE $2_{{\nu}3}$ BAND OF METHANE AT 1.7 $\mu$

Abstract

Work has been continued on the measurement of optical dispersion of gases in the infrared for the purpose of obtaining absolute intensities of rotational lines. The opical dispersion of methane at atmospheric pressure has been determined through the $2\nu_{3}$ overtone band at 1.7$\mu$. The change in refractive index, on passing through the strongest lines amounts to about $3\times 10^{-6}$. The accuracy of the measurement of refractive index is $\pm 1 \times 10^{-7}$. A dispersion curve will be presented showing details of the P and R branches and also individual lines in the Q branch. The line intensities will be given. Calculation of line widths, however, involves the application of a complicated slit width correction and this has not yet been carried out successfully.