Frances Pleasonton

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Frances Pleasonton
Alma materBryn Mawr College
Known forNeutron decay
Scientific career
InstitutionsOak Ridge National Laboratory

Frances Pleasonton (1912–1990) was a Particle Physicist at the Oak Ridge National Laboratory. She was an active teacher and researcher, and a member of the team who first demonstrated neutron decay in 1951.

Early life and education[edit]

Pleasonton earned her Bachelor's degree at Bryn Mawr College.[1] She was an editor of the Bryn Mawr College yearbook.[2] She went on to teach at Winsor School, Girls Latin School of Chicago and Brearley School.[1] She returned to Bryn Mawr College for her Master's degree, working as a Warden at Pembroke East, and graduated in 1943.[1][3] She was demonstrator-elect in physics and took a leave of absence for government service in 1942.[3] During her Master's degree she identified the crystal structure of Rochelle salt.[4]


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]


  1. ^ a b c College, Bryn Mawr (1944). Bryn Mawr College Calendar. Bryn Mawr College.
  2. ^ "Bryn Mawr College Yearbook. Class of 1934". Bryn Mawr College. Retrieved 2018-06-15.
  3. ^ a b Bryn Mawr College (1944). Bryn Mawr College Calendar, 1943-1944. Special Collections Bryn Mawr College Library. Bryn Mawr, PA: Bryn Mawr College.
  4. ^ Pleasonton, Frances (1944). "A Model of the Structure of Rochelle Salt". American Journal of Physics. 12: 19–22. doi:10.1119/1.1990525.
  5. ^ a b c "The short life of a neutron | ORNL". Retrieved 2018-07-15.
  6. ^ a b "History of Fundamental and Applied Sciences Achievements in Oak Ridge National Laboratory: Nuclear Physics and Astrophysics – Discovery of America by Queltanews - Technopark QUELTA". Retrieved 2018-07-15.
  7. ^ Pleasonton, Frances; Snell, A. H. (1957-08-07). "Ionization following internal conversion in xenon". Proc. R. Soc. Lond. A. 241 (1225): 141–152. Bibcode:1957RSPSA.241..141P. doi:10.1098/rspa.1957.0119. ISSN 0080-4630.
  8. ^ "Fragment-mass and kinetic-energy distributions from the spontaneous fission of $sup 246$Cm | Sci-napse | Academic search engine for paper". Scinapse. Retrieved 2018-07-15.
  9. ^ Pleasonton, Frances (1973-10-15). "Prompt γ-rays emitted in the thermal-neutron induced fission of 233U and 239Pu". Nuclear Physics A. 213 (2): 413–425. Bibcode:1973NuPhA.213..413P. doi:10.1016/0375-9474(73)90161-9. ISSN 0375-9474.
  10. ^ a b Bienlein, J.K.; Pleasonton, Frances (1962-08-01). "The half-life of He6". Nuclear Physics. 37: 529–534. Bibcode:1962NucPh..37..529B. doi:10.1016/0029-5582(62)90288-2. ISSN 0029-5582.
  11. ^ Perey, F. G. (1973). "Report to the US Nuclear Data Committee". OSTI. Retrieved 2018-07-15.
  12. ^ Proceedings of the Royal Society of London: Mathematical and physical sciences. Harrison and Son. 1957.
  13. ^ "TENNESSEE CITIZENS FOR WILDERNESS PLANNING" (PDF). 1981-11-09. Retrieved 2018-07-15.