Radiative cooling with selectively infrared-emitting gases

Gases which are strongly emitting only in the 8–13-μm wavelength range can be employed for radiative cooling to low temperatures. We carried out a general discussion of molecular vibration and rotation to identify a number of candidate gases. Three of the most promising ones—ammonia, ethylene, and ethylene oxide—were then studied in detail. Infrared transmittance spectra were recorded for 5–50 μm by spectrophotometry. These data were used to compute the basic cooling parameters and the relation between cooling power and temperature difference for pure and mixed gases. The results of some practical field tests of radiative cooling are reported.