Total Absorptance of Ammonia in the Infrared*

Abstract

The total or integrated absorptance ∫A(ν)dν has been measured at 26°C for the ammonia bands near 950, 1628, and 3300 cm−1 in samples of pure ammonia and of ammonia mixed with nitrogen. The results are displayed graphically with ∫A(ν)dν shown as a function of absorber concentration w and an equivalent pressure Pe, which depends upon the partial pressures of the two gases. The equivalent pressure of a given sample is expressed in terms of the total pressure of the sample, the partial pressure of ammonia, and a self-broadening coefficient B, which is related by simple kinetic theory to the ratio of the optical collision diameters of ammonia and nitrogen. The graphs can be used to predict the total absorptance of ammonia in any sample at laboratory temperature for which the values of w and Pe are known, provided these values lie within the range covered in the present study. Values have been obtained for the band strengths S=∫k(ν)dν for the absorption bands studied. The self-broadening coefficient B for ammonia is greater than the corresponding values for telluric gases obtained in earlier studies.