Knowledge Bank

The far infrared collision induced absorption (CIA) of gas phase cyclopropane (CP) and cyclopropane-rare gas mixtures has been observed. The absorption coefficient for the CP-CP CIA is $\gamma max(70cm-1)=7.3\times 10-5(cm-1amagat-2)$ using $I(\nu ~)/I0(\nu ~)=\exp (-\gamma (\nu ~)IP2)$ Where $\ell$ is the cell length and $P2$ is the pressure square. The theoretical band calculated from the superposition of translationally broadened rotation lines using the literature value of the isotropic polarizability and quadrupole moment of CP with Lennard-Jones pairwise distribution function and a normalized line shape function peaks at $60m-1$ with an absorption coefficient several times smaller that the observed value. This is absorption coefficient several times smaller that the observed value. This is contrasted with the observed CIA results of other nonpolar hydrocarbons (i.e., allene, ethane, ethylene) which exhibited maxima in CIA bands at frequencies much higher than that calculated from this quadrupole-polarizability term. The frequency distribution of the band for cyclopropane is similar to the results of the more isotropic molecules such as $N2$ and $CH4$. Intensity variation will be discussed.