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.