# ACETYLENE SPECTRA OBSERVED IN N-TYPE STARS: A LABORATORY STUDY

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 Title: ACETYLENE SPECTRA OBSERVED IN N-TYPE STARS: A LABORATORY STUDY Creators: Rinsland, C. P.; Rao, K. Narahari; Baldacci, A.; Ciorcianni, S. Issue Date: 1979 Publisher: Ohio State University Abstract: The molecule acetylene has been recently detected from infrared spectra of several cool carbon $stars.^{1,2}$ Since $C_{2}H_{2}$ is a useful probe of the chemical composition and temperature structure of the upper atmospheres and circumstellar shells of these objects, we have studied the bands observed in stellar spectra in the laboratory using the Ohio State University 10-m focal length Czerny-Turner vacuum grating spectrometer. Positions, accurate to $\pm 0.005 cm^{-1}$, have been measured for 3000 lines in the 3 $\mu m$ region using samples heated to 160 C. Since elevated temperatures and high resolution were used, the molecular constants have been improved for previously assigned bands as well as many new transitions have been observed. Absolute strengths of 100 lines in the 7 strongest bands in the 3 $\mu m$ region have been measured, including the $\nu_{1} + \nu_{5}^{1}$ band of $^{12}C^{13}CH_{2}$. Absolute strengths of 1.67 and $0.290 cm^{-2}$ $atm ^{-1}$ at 300 K have been determined for the integrated Q branch strength of the $\nu_{1}+\nu_{5}^{1}$ band at $4091 cm^{-1}$ and the $\nu_{2+}\nu_{5}^{1}$ band at $2701 cm^{-1}$, respectively. These values have been used to provide revised estimates of $3 \pm{1}\times 10^{18} mol\ cm^{-2}$, and $T_{R}^{\cong} 300 K IRC+10^{\circ} 216$. The total internal partition function of $^{12}C_{2}H_{2}$ has been evaluated in the temperature range 200 to 350 K from a tabulation of rotational and vibrational constants of all bands within $2200 cm^{-1}$ of the ground state. The present work has been combined with results from previous studies to deduce improved ground state constants for $^{12}C_{13}CH_{2}$ of $B=1.148115 \pm 18 cm^{-1}$ and $D=1.550 \pm 11 \times 10^{-6} cm^{-1}$. Description: Author Institution: URI: http://hdl.handle.net/1811/10751 Other Identifiers: 1979-FA-07