Method of and apparatus for non-equilibrium chemical kinetic separation of deuterium from hydrogen are described wherein hydrogen with its normal abundance of deuterium and an appropriate reactant, bromine, are supplied to a deuterium reaction vessel wherein they are vibrationally excited by, for example, being exposed to a volumetrically scalable ionizing-sustainer electrical discharge effective to provide vibrational excitation of the H.sub.2 and HD following which selective intermolecular vibration-vibration energy pumping occurs giving conditions effective to produce an HBr/DBr product mixture. The ionizing-sustainer discharge is effective to generate vibrational excitation from which follows chemical reactions that produce DBr and HBr at such relative rates that the mixture is enhanced in deuterium content relative to said content of the entering hydrogen stream. For the production of heavy water, the DBr and HBr are then dissolved in water. This water is then reacted with oxygen to chemically separate the bromine and the bromine is removed to leave water enriched in deuterium. Additional DBr/HBr product mixture is then dissolved in this deuterium enriched water and the process repeated to produce water having the deuterium content of the product DBr/HBr.