AbstractRaman frequencies for the totally‐symmetric NSi3stretching mode of14N(SiH3)3and15N(SiH3)3have been carefully compared. In the gas phase the isotopic shift is zero within experimental error, which indicates planar trigonal geometry for the heavy‐atom skeleton. For the liquid and solid phases there are small but real isotopic shifts. The skeleton is therefore slightly distorted in these phases, but it is impossible to say just how.Complete Raman and infrared data are given for14N(SiH3)3in several physical sta