Fourier transform spectroscopy of C4H (butadiynyl) in Ar at 10 K: C–H and C≡C stretching modes

Abstract

A Fourier transform infrared (FTIR) isotopic study of the C4H (butadiynyl) radical produced by trapping the products from the vacuum ultraviolet photolysis of diacetylene (C4H2) and 1,3-butadiene (C4H6) in solid argon at 10 K has been carried out in the midinfrared from 400–3900 cm−1. A variety of carbon-13 and deuterium substituted C4H2 and C4H6 parent molecules were used to produce various isotopomers of C4H. On the basis of their isotopic behavior two absorptions at 3307.4 and 2083.9 cm−1 have been assigned to the ν1, C–H stretching and ν2, C 3/4 C stretching modes. The previous identification of the other C 3/4 C stretching mode, ν3=2060.6 cm−1, which was based on the effects of deuteration, has been confirmed and the corresponding frequencies for various 13C-substituted isotopomers have been measured. The following frequencies have been obtained for ν1, ν2, and ν3 for C4H isotopomers: 3307.2, 2078.9, and 2023.8 cm−1 for H–C 3/4 C–C 3/4 13C; 3307.2, 2069.9, and 2032.5 cm−1 for H–C 3/4 C–13C 3/4 C; 3307.2, 2066.8, and 2054.0 cm−1 for H–C 3/4 13C–C 3/4 C; 3293.3, 2048.9, and 2057.4 cm−1 for H–13C 3/4 C–C 3/4 C; 3292.5, 2050.6, and 2024.6 cm−1 for H–13C 3/4 C–C 3/4 13C; 3292.5, 2050.6, and 2030.0 cm−1 for H–13C 3/4 C–13C 3/4 C; 3306.3, 2063.3, and 2019.5 cm−1 for H–C 3/4 13C–C 3/4 13C; 3306.3, 2050.6, and 2018.0 cm−1 for H–C 3/4 13C–13C 3/4 C; 3290.1, 2007.9, and 1981.6 cm−1 for H–13C 3/4 13C–13C 3/4 13C; and 2579.3, 2056.5, and 2049.7 cm−1 for D–C 3/4 C–C 3/4 C.