Fundamental and combination bands of CO2–C2H2 and CO2–C2D2 in the mid-infrared region

Abstract

Spectra of the weakly bound CO2–C2H2 and CO2–C2D2 complexes are observed in the regions of CO2 ν3 (≈ 2349 cm−1) and C2D2 ν3 (≈ 2440 cm−1) fundamental vibrations, using an infrared optical parametric oscillator to probe a pulsed supersonic slit-jet expansion. Five bands are measured and analysed: the fundamental asymmetric stretch of the C2D2 component, two combination bands involving the out-of-plane torsional vibrations (C2D2 ν3 + torsion and CO2 ν3 + torsion) for CO2–C2D2, and two combination bands involving an intermolecular in-plane bending vibration for CO2–C2H2 and CO2–C2D2. The resulting intermolecular frequencies are 61.408(1), 54.5(5), 39.9(5), and 39.961(1) cm−1 for CO2–C2H2 and CO2–C2D2 in-plane vibrations, and CO2–C2D2 out-of-plane torsional vibrations in CO2 and C2D2 regions, respectively. This is the first experimental determination of these intermolecular vibrational frequencies.