Bridges Across the Infrared-Radio Gap

The wide gap which exists between the generation and detection of coherent radiation on one hand, and the generation and detection of submillimeter incoherent radiation on the other hand, is discussed from the standpoint of spectroscopy. While the resolving powers possible with microwave spectroscopy can be indefinitely extended with refinements in technique, the resolving powers possible with infrared spectroscopy are subject to an upper limit determined by the size of the external optics utilized. In the far infrared at wavelengths greater than 10 microns the resolving powers obtained in the past have been subject to further instrumental limitations, but the attainment of the optically allowable resolving powers appears possible now with recent developments in infrared spectroscopic instrumentation.