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Earlier studies of the direct photolytic decomposition of t-butyl azide, $(CH3)3CN3$, or trimethylsilyl azide, $(CH3)3SiN3$, or their substituted congeners showed little evidence for the production of triplet nitrene intermediates. Furthermore, the absence of the expected imine photoproduct with the silicon analog suggested substantially different chemistry. The independent existence of the t-butyl nitrene radical $(CH3)3CN$ has been previously confirmed by sensitized photolysis experiments. Here, signals attributable to triplet trimethylsilylnitrene, $(CH3)3SiN$, are reported. Fragmentation products formed when trimethylsilyl azide vapor interacts with matastable $N2$ or Ar generated in a microwave discharge were trapped in $N2$ or Ar matrices at 10 K. The ESR spectrum showed a strong xy line near 8000 G, indicating an axially symmetric triplet ground state molecule with $D-1.56cm-1$. The line appears as a poorly resolved triplet split by 13.5 G. comparable to the N hyperfine observed in other nitrenes. This signal could not be produced by photolysis, and decayed on UV irradiation or annealing to $T>35K$. IR studies indicated a set of new bands that followed the behavior of the ESR line; these were substantially different from IR spectra produced by photolysis. Examination of the data suggests the formation of triplet trimethylsilylnitrene.