Low pressure tritiation of molecules

Molecules are tritiated by depositing molecules of a substance to be tritiated on a supporting substrate in a vacuum chamber, and then subjecting the substance to low pressures of tritium gas. In a second embodiment of the invention, a substance is tritiated by placing the same near, but not in the path of, an electron beam which traverses a chamber; admitting tritium gas into the chamber; and subjecting the tritium to the electron beam thereby generating vibrationally excited tritium gas molecules which collide and react with the substance thus incorporating tritium atoms into the substance