The combination of a microwave excitation source with a small spectroscope mounted in focus to a 35 mm camera (Figure 1) has proved to be rapid and relatively simple for the identification of various gases. The source is a standard magnetron unit, type CMD-4, from Raytheon which produces microwave power of 10 to 100 watts at a frequency of 2450 megacycles. Both the excitation source and the spectroscope-camera are compact and portable and can be used under a wide variety of conditions. All parts are comparatively inexpensive and easily assembled.
J. W. Mellichamp, I. Adams, and G. A. Wolff, "Gas Identification with Microwave Excitation and a Small Spectroscope-Camera," Appl. Spectrosc. 15, 52-53 (1961)