In December 1966, Leona married Willard Libby, who had received the 1960 Nobel Prize in chemistry for his work with radiocarbon dating. Leona worked on numerous problems and issued nearly sixty publications during her time in Colorado.
Leona worked in conjunction with Libby on about ten papers. After moving to the University of California in Los Angeles in 1970, she created a research program to examine past climates by analyzing isotope data in ancient wood samples. Her second book, Past Climates: Tree Thermometers, Commodities, and People, was published in 1983. The Isotope People remains an unpublished manuscript.
Throughout the years and every place Leona traveled, she and her companions would talk of problems from many different fields. One example shared while traveling to her work at the Argonne Lab was the computation of "the cross section of an automobile for collision with other automobiles, using 50,000 crashes per year, 20 million cars, and putting them all on two-lane roads." 6 In an interview with John Marshall, her second son, he recounted continual conversations between Leona and Bill Libby in their home, at their work, and when they traveled "because Leona was having fun constructing all sorts of theoretical scenarios." 7
Leona Libby died on November 10, 1986, at Saint John's Hospital in Santa Monica, California. She had most recently been examining spectroscopic data from quasars and found tentative evidence for the fission products of superheavy elements. At the time of her death she was an adjunct professor of environmental science and engineering at the University of California at Los Angeles and a consultant to the Los Alamos Scientific Laboratory. Her published works include her books and two hundred articles.
At the fiftieth anniversary of the CP-1 in November 1992, four women were honored as pioneers in nuclear science. Leona Woods Marshall Libby was one of those women. She was in the company of Lise Meitner, Marie Curie, and Irène Joliot-Curie.