New technique for measuring the refractive index of gases near 10 microm

A method to measure quickly and easily the index of refraction of gases near 10 microm using a Mach-Zehnder interferometer and a discretely tunable CO(2) laser is described. This technique employs the use of two gas cells positioned at 45 degrees to the incident beams in adjacent arms of the interferometer. By translating these cells in a direction perpendicular to the beam direction, a shift in the fringe pattern occurs due to the change in the optial path. Gases investigated include SF(6) and CCl(2)F(2).