ABSTRACT
This chapter provides to incorporate spectroscopic gas properties into the basic equations of radiative transfer, so as to present a realistic means of analyzing radiative transfer within real gases. For this purpose specific restriction will be made to infrared gaseous radiation, which results from molecular transitions involving both vibrational and rotational energies, with emphasis on the application of molecular band models to radiative transfer analyses. The chapter discusses spectroscopic models describing the total band absorptance for infrared radiating gases. Infrared absorption and emission of thermal radiation is a consequence of coupled vibrational and rotational energy transitions. While the location of a vibration-rotation band is described by the associated vibrational transition, the band structure is governed by simultaneous rotational transitions that accompany the vibrational transition. Vibrational transitions spanning three vibrational levels produce the first overtone band, located at twice the fundamental frequency of the molecule, and subsequent overtone bands occur at higher multiples of the fundamental frequency.
