INFRARED TRANSMITTANCES OF INHOMOGENEOUS GASES DETERMINED FROM HOMOGENEOUS GAS DATA.
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Date
1965
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Ohio State University
Abstract
Some earlier work reported from this $laboratory^{1}$ pointed out the effect of the band-pass nature of a monochromator on the measured spectral transmittances of gases and presented a method for dealing with this effect with fair accuracy when working with inhomogeneous optical paths. Recently, more exacting experiments and a better theoretical treatment have produced a five-fold improvement in the agreement between theory and experiment. Measurements were made of the spectral transmittances of inhomogeneous paths of hot gas which consisted of series of homogeneous zones. The transmittance of each zone was measured separately, as was the transmittance of the entire multizone assembly. Water vapor in two furnace-heated quartz cells in series was studied in the $2.7\,\mu$ region. Inhomogencity was obtained by having the two cells at different temperatures and/or pressures. A row of flat flames, each burning a different mixture, generated suitable series of homogeneous zones containing $CO_{2}$. The $4.3\,\mu$ bands of $CO_{2}$ were investigated with hot samples produced in this way. The measured transmittance of each inhomogeneous path was compared with a transmittance calculated from the zonal transmittances, using the Curtis-Godson approximation in conjunction with a random band $model.^{2}$ The formulae depend on the parameter $x =S_{\rho}l/2\pi\gamma$, where S is mean line strength, p partial pressure of absorber, l path length, and $\gamma$ mean line half width, for the spectral interval considered. When the inhomogeneous path is low x or each homogeneous zone is high x, the formulae require as input data only the measured transmittances of each separate homogeneous zone. A general formula for the inhomogeneous transmittance was developed for the case when each zone is medium or high x. This requires a knowledge of the transmittance and only an approximate value of x for each homogeneous zone.
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Supported by NASA --- Marshall Space Flight Center.
Author Institution: The Warner \& Swasey Company Control, Instrument Division 32--16
Author Institution: The Warner \& Swasey Company Control, Instrument Division 32--16