Laser Irradiation of Monomeric Acetylene and the T-Shaped Acetylene Dimer in Xenon and Argon Matrices

Abstract

Irradiation of acetylene (4) in an argon matrix with an ArF laser (λ = 193 nm) yields the ethynyl radical C2H· (5) and C2 (6). If the same wavelength is used to irradiate 4 in a xenon matrix, only the infrared signal of the compound Xe–C2 (7) can be detected. The same band is found on irradiation at λ = 248 nm (KrF laser) in a xenon matrix, despite the fact that acetylene (4) does not absorb light of this wavelength. Irradiation of the T-shaped acetylene dimer 9 in an argon or xenon matrix at λ = 193 nm yields butadiyne (11) and vinylacetylene (12). However, irradiation with a KrF laser (λ = 248 nm) in a xenon matrix additionally yields cyclobutadiene (13). The dependence of the mechanisms of the fragmentation and dimerization of acetylene (4) on the matrix material is discussed.