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 nu(1) and nu(3) modes of C2H to be 3293.3 and 1835.7 cm(1), respectively. The fundamental C-H stretching nu(1) mode of C2H was determined for the first time in solid Ne. (C) 2008 Elsevier B.V. All rights reserved.