HIGH-DISPERSION MEASUREMENTS ON $\sigma_{2}$ OF $NO_{2}$ AT $175^{\circ} C$$^{*}$
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Date
1954
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Ohio State University
Abstract
The vibration-rotation band $\sigma_{2}$ of $NO_{2}$ originally observed prismatically by Bailey and $Cassie^{1}$ and by $Schaffert^{2}$ has been reexamined with a 1200 lines-per-inch grating. The sample was contained in a 10-cm monel cell closed with silver chloride windows at a temperature of $175^{\circ} C$ and a pressure of 45 cm of mercury. This band extends from about 650 K to 900 K and consists of lines which vary in separation from about 9 K at the low-wave-number end to 19 K at the high-wave-number end. It was necessary to record at high temperature because the central region of the band is completely obscured by a band of $N_{2}O_{4}$, with which $NO_{2}$ exists in equilibrium at ordinary temperature. The band has the appearance of a perpendicular band for a symmetric top, with the exception that the convergence of the lines is not uniform. The convergence is interrupted at the band center by the abnormal spacing of $^{R}{Q}_{O}$, $^{R}{Q}_{1}$, $^{P}{Q}_{1}$, $^{P}{Q}_{2}$. $^{R}{Q}_{O}$ and $^{R}{Q}_{1}$ are unsymmetrical in form, shade off toward high wave numbers, and appear to be too close together. $^{P}{Q}_{1}$ and $^{P}{Q}_{2}$ shade off toward low wave numbers and are too close together. The central pair $^{R}{Q}_{O}$ and $^{P}{Q}_{1}$ are too far apart. A band analysis carried out with symmetric top assumptions and neglecting the four central lines gives a band center of $749.6_{5} K$ and $\Delta(A-B)$ of 0.337 K. This band center differs by 1.2 K from the value 750.9 K quoted by Moore . Rotational constants obtained from this analysis are ($A^{\prime\prime}-B^{\prime\prime}) = 7.58_{3} K$, and $(A^{\prime}-B^{\prime}) = 7.92_{3} K$. The difference between these numbers, 0.340 K, is in good agreement with the slope of the band center graph quoted above. A value of $D^{\prime}_{K}=D^{\prime\prime}_{K} 2.59 \times 10^{-3} K$ may be obtained as the slope of the $(A - B)$ graphs. This is about one-half the value quoted by $Moore^{3}$.
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$^{*}$This work was supported by the Office of Ordnance Research, U. S. Army. $^{1}$ C. R. Bailey and A. B. D. Cassie, Nature 131:239, 910 (1933) $^{2}$ R. Schaffert, J. Chem. Phys. 1:507 (1933) $^{3}$ G. Moore, J.O.S.A. 43:1045 (1935)
Author Institution: The University of Tennessee
Author Institution: The University of Tennessee