Knowledge Bank

Infrared spectrum of the weakly-bound CO$2$--C$2$H$2$ complex in the region of the CO$2$ $\nu 3$ fundamental band ($\sim$ 2349 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) is observed in a pulsed supersonic slit jet expansion using a tunable diode laser probe. Two bands are observed and analyzed: the fundamental (C--O asymmetric stretch) and a combination involving the intermolecular torsional (out-of-plane bend) vibration. The resulting torsional frequency is 44.385(10) cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. This represents the first observation of an intermolecular frequency for carbon dioxide-acetylene complex. A comparison between the results obtained here and those previously reported for N$2$O--C$2$H$2$ complex is discussed.