in 1948, following the establishment of a nuclear sciences team at the dsir, rafter was sent to the united states to train in radiochemistry and to visit nuclear establishments in the united states, canada and england. on rafter's return, he began to work with the new technique of radiocarbon dating, which dates organic material by comparing the ratio of radiocarbon atoms (carbon-14) to regular carbon atoms (carbon-12) with established radiocarbon: carbon ratios from the past. rafter first used the method to date moa bones and ash showers from volcanos on the north island of new zealand. after difficulties with the process published by willard libby, radiocarbon dating’s american pioneer, rafter worked with dsir physicist gordon fergusson and their team to perfect a new and reliable method of radiocarbon dating using carbon dioxide gas rather than solid carbon.