A SYSTEMATIC INVESTIGATION OF CONCENTRATION VARIATIONS OF ATMOSPHERIC TRACE GASES PASSED THROUGH TUBINGS OF DIFFERENT MATERIALS USING A FOURIER TRANSFORM INFRARED (FT-IR) $SPECTROMETER^{a}$

$^{a}$Financial support from the Center for the Study of Terrestrial and Extraterrestrial Atmospheres (NASA NAGW-2950) and the NASA Lewis Research Center (NAG3-1677) is gratefully acknowledged.Author Institution: Laser Spectroscopy Laboratory, Department of Physics and AstronomyRovibronic spectra of the fundamental bands of $^{3}2S^{\bot}6O_{2}, ^{1}4N^{1}6O$ and its isotopomers of HCL ($^{1}H^{3}5Cl$ and $^{1}H^{3}7Cl$) have been recorded using Nicolet Magna-IR 550 Fourier Transform Infrared spectrometer in the region $400 - 4000 cm^{-1}$ spectral region, under quasi-static conditions, when the sample gas was passed in turn through tubings of aluminum, copper, stainless-steel and teflon. The absorbances were measured for the individual rotational lines corresponding to the three modes of vibration ($\nu_{1}$-symmetric stretch, $\nu_{2}$- symmetric bend, $\nu_{3}$-antisymmetric stretch) of the $SO_{2}$ molecule for the pressures in the range 50-250 Torr range. The absorbances were also measured for the rotational lines of the isotopomers HCl for pressures in the range 100-1000 Torr range; and for the NO molecule in the range 100-300 Torr. A plot of absorbance versus pressure for all the observed transitions showed a linear relationship, thereby validating Beer's law for the chosen pressure ranges. A measurable difference in the absorbance peaks was observed for HCl and NO confirming the interaction of these molecules with the corresponding tubing materials. Quantifiable changes in the absorbance peaks were not observed for the $SO_{2}$ molecules flowing through the different tubing materials. A detailed and systematic analysis pertaining to the observed concentration changes of the trace gases studied will be presented