Infrared absorption spectra of ethynyl radicals isolated in solid Ne: Identification of the fundamental C–H stretching mode

Irradiation of a sample near 3.0 K of ethyne, C2H2, in a Ne matrix with vacuum ultraviolet radiation from a synchrotron produced various photoproducts that were analyzed through their infrared absorption spectra. Photolysis with light at 171 nm yielded as major product ethynyl radical, C2H. Based on observed D-isotopic shifts and comparison of observed vibrational wavenumbers and isotopic ratios with values predicted with quantum-chemical calculations, we identified the ν1 and ν3 modes of C2H to be 3293.3 and 1835.7 cm−1, respectively. The fundamental C–H stretching ν1 mode of C2H was determined for the first time in solid Ne.