Yoshida, T., Tanabe, T., Okabe, Y., Sawasaki, T. and Chen, A. Decomposition of Carbon Dioxide by Metals during Gamma Irradiation. Radiat. Res. 164, 332–335 (2005). We have proposed a technique to enhance the decomposition of carbon dioxide by γ irradiation. This is possible by putting metal components into CO 2 gas to promote the conversion of γ rays to lower-energy electrons through Compton, photoelectron and cascading electron knock-on events in metals. Numerical simulations using the EGS code indicated that the number of lower-energy electrons ejected from metals into CO 2 gas increases with increasing Z number and/or density of the metals; this was supported by the experimental results, i.e., the CO 2 -containing metals with a higher Z number exhibited a greater efficiency for production of CO. In addition, production of CO could be enhanced by carefully controlling the volume and surface area of metal components as well as the proximity to adjacent metal components. These experimental results successfully demonstrated that modification of the kinds of metal components and metal structures can control the energy and the number of electrons ejected from the metals and can lead to enhancement of production of CO from CO 2 .