Knowledge Bank

The spectrum of gaseous cyclopropane, $C3H6$, has been observed between 10,000 and $16,000cm-1$ with a high resolution Fourier Transform Spectrometer at a pressure of $13.3$ kFa (100 Torr). The $4-0$ and $5-0$ vibrational overtone bands of the C-H stretch have been observed using a Local mode $model1$ to assign the spectrum, and absolute absorption cross sections have been measured. The 4--0 band has not previously been observed. The $5-0$ band has recently been used as the standard far photoacoustic cell $calibration.2$ The maximum absorption cross section for this band, at $14055.1cm-1$ is $\sim 5.2\times 10-24$ $cm2$. This band is ideally suited for photoacoustic cell calibration because it is broad and contains no rotational line structure. It is easily accessible with a dye laser, and variations in the laser frequency and bandwidth will be unimportant in the calibration. In additional the fast vibrationt-translation relaxation rates guarantee complete thermalization of the absorbed energy.{$\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}$ This work was supported in part by AFWL Contract F29601--82--C--0019 and supported in part under the McDonnell Douglas Independent Research and Development Program.} 1. R. G. Bray, SPIF Vol. 236, Laser Spectroscopy for Sensitive Detection, pp 9--17 (1980). 2. S. A, Lawton-u S. L. Bragg and C, B, Wiswall, Absorption Spectra of Atmospheric Gases Near the 1.315 $\mu$m Iodine-Atom Laser Line"", Proceedings of the Lasers ‘82 Symposium (In press).