Matrix isolation infrared observation of H_xSi(N ₂)_y, (x = 0, 1, 2 and y = 1, 2) transient species using a 121-nm vacuum ultraviolet photolysis source

Vacuum ultraviolet photolysis (121.6 nm) of silane in a nitrogen matrix at 12 K leads to the observation of several transient species, which have been characterized using Fourier transform infrared spectroscopy. Four transient species containing silicon and nitrogen have been observed (SiN₂, Si(N₂)₂, HSiN₂, and H₂SiN ₂), and one transient species containing only silicon and hydrogen has been observed. The assignment of the infrared bands due to each of these species is accomplished by performing isotopic substitution experiments (SiD₄, ¹⁵N₂, and mixtures with SiH₄ and ¹⁴N₂), matrix annealing experiments, UV-visible photolysis experiments, by comparison with previous experimental matrix isolation frequencies, where available, and for HSiN₂ and H ₂SiN₂ by comparison to B3LYP/aug-cc-pVTZ-calculated vibrational frequencies. The observation and infrared assignment of the HSiN₂ and H₂SiN₂ molecules in these experiments is significant in that HSiN₂ has not been previously reported in the matrix isolation literature, and H₂SiN₂ has only been reported once previously by a different route of formation. The energetics of the overall formation pathways for the molecules observed in these experiments is discussed using B3LYP/aug-cc-pVTZ calculations.