MEASUREMENTS OF THE $\nu_{3}$ BAND HCN BROADENED BY $N_{2}$ AND BY HF

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1983

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Ohio State University

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$N_{2}$-broadened halfwidths have been measured for 51 lines belonging to the $\nu_{3}$ fundamental band of hydrogen cyanide ($^{1}H^{12}C^{14}N$). Data were obtained at room temperature ($\simeq$299K) using a Fourier transform interferometer spectrometer with a nominal resolution of $0.06 cm^{-1}$. Spectra were recorded in the region from 3200 to $3400 cm^{-1}$, using a 10-cm absorption cell with broadening gas pressures varying from 150 to 700 torr. The halfwidth values were obtained through a nonlinear least squares spectral fitting procedure, and are generally consistent from scan to scan. The resulting $N_{2}$-broadened halfwidths, determined for all lines with $j\leq 25$ in both the P and R branches, are smaller than $CO_{2}$-broadened halfwidths, but larger than Ar-broadened halfwidths measured for the same $band^{1}$, and also show a decrease in halfwidth for increasing J. HF-broadened HCN halfwidths have also been measured in spectra of 3 separate 10-cm absorption cells, each filled to a total pressure of approximately 150 torr with a 50-50 mixture of HF and $N_{2}$ and containing several hundred ppm of HCN. An oscillatory dependence of the halfwidth on m, indicative of near-resonant dipole-dipole interactions between HF and HCN, has been observed and is consistent with a similar m-dependence previously measured for HCN broadened by HC$\ell .^{1}$ $^{1}$R. J. Thibault, A. G. Maki and E. K. Plyler. J. Opt. Soc. Am. 53, 1255 (1963).

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Author Institution: Mail Stop 401A NASA, Langley Research Center Hampton

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