The Refractive Index of Methyl Chloride at 10 Gc/s

The dielectric behaviour of gases in an electromagnetic field has been studied theoretically by Van Vleck and Weisskopf (1945). They found expressions for the contributions to the absorption coefficient a and the refractive index n at a frequency v arising from transitions between quantum states j and i. If v is much less than the natural frequency Vii associated with the transition, and if the line width is also small compared with Vii' their results give: