a gas decomposition reactor for the decomposition of a gas into a mixture of solid and gaseous by - products is disclosed . the gas decomposition reactor includes a reactor vessel , a raman spectrometer , and a processor . the reactor vessel has an inlet for receiving inlet gas and an exhaust outlet for releasing exhaust gas . the raman spectrometer is connected with the exhaust outlet for determining a chemical conversion within the reactor chamber and generating a corresponding signal . the processor is connected with the raman spectrometer to receive the signal from the raman spectrometer . the processor is capable of comparing the signal with a set of values and calculating differences between the signal and the set of values . the processor is connected with the inlet to regulate a flow of the inlet gas .