We report the first observation of the vibrational Raman spectrum of hydrogen molecules H2 in crystalline silicon treated with hydrogen atoms at 400 °C. The Raman spectrum of H2 in silicon observed at room temperature exhibits a frequency shift of around 4158 cm-1 and a very broad half-width of approximately 34 cm-1. An isotope shift was also detected at around 2990 cm-1 in silicon treated with deuterium atoms at 400 °C. The frequency shifts of the observed lines are in close agreement with those reported for H2 and D2 in the gas, liquid, and solid phases
