A Fourier transform infrared study has resulted in the first observation of a vibrational spectrum of the nonplanar H2SiCCH radical produced by trapping the products of the vacuum ultraviolet photolysis of a mixture of SiH4 silane, and C2H2 acetylene, in an Ar matrix at similar to 10 K. Two vibrational fundamentals have been observed, the nu(3)(a＇), silicon-carbon stretching mode at 2055.6 cm(-1) and the nu(4)(a＇), hydrogen-silicon bending mode at 926.8 cm(-1). The Vibrational frequencies, relative intensities, and extensive measurements of D and C-13 isotopic shifts are all in good agreement with the values predicted by new density functional theory calculations.