Pleasonton was an active researcher in neutron decay.[5] There were several attempts to measure neutron half-life before the second world war, all of which failed due to the lack of availability of intense neutron sources.[5] Arthur Snell and Leonard Miller built the Oak Ridge Graphite Reactor, which could focus beams of neutrons and allow scientists to observe their decay.[5] They measured the half-life of a neutron in 1951.[6] Pleasonton was supported by the United States Atomic Energy Commission and published broadly.[7][8][9] In 1958 they examined the decay of helium-6, Pleasonton and Snell monitoring the directions of neutrinos and electrons.[10] This result confirmed the electron-neutrino theory of beta decay.[6] In 1973 she authored several sections of the report for the Nuclear Regulatory Commission.[11] At Oak Ridge National Laboratory, Pleasonton's laboratory was visited by the Queen of Greece and the King of Jordan.[10] Pleasonton went on to study the ionisation of xenon x-rays.[12]
Pleasonton remained in Tennessee after her retirement from Oak Ridge National Laboratory and was involved in citizens groups to protect the environment.[13]
