Edward Mills Purcell
Edward Mills Purcell ( born August 30, 1912 in Taylorville, Illinois, † March 7, 1997 in Cambridge, Massachusetts ) was an American physicist and Nobel laureate.
Life
Purcell graduated from Purdue University (Bachelor 's degree in Electrical Engineering, 1933) and Harvard University, where in 1935, his master's degree made , and in 1938 received his doctorate. After that, he was from 1941 to 1946 at the Radiation Laboratory of the Massachusetts Institute of Technology and from 1938 first instructor at Harvard and from 1949 Professor of Physics ( 1950-1971 and senior fellow of the University ). From 1980 he was a professor emeritus.
Purcell discovered in 1945, the nuclear magnetic resonance ( NMR), and independent of it about the same time Felix Bloch. This discovery was the basis for the development of nuclear magnetic resonance spectroscopy (NMR ) spectroscopy, with the help of, for example, the structure of molecules can be studied and the wide-ranging application in the natural sciences and medicine (eg MRI ) place. Purcell is known in this regard for he developed together with Herman Y. Carr called Carr -Purcell pulse sequence.
In 1951, he discovered along with Harold Irving Ewen and Gart Westerhout the emission of the frequency of 1.42 GHz ( 21 -centimeter line) of atomic hydrogen of the Milky Way, which is caused by the change in the orientation of the electron spin relative to the nuclear spin. It had been predicted theoretically in 1944 by Hendrik Christoffel van de Hulst.
The 21 -centimeter line is practically not detectable in the laboratory, but is emitted by highly diluted interstellar gas in sufficient strength in space and is equipped with sensitive antennas on Earth detectable ( → Radio Astronomy ). Purcell and Norman Ramsey were the first to tackle the (now disproved ) CP symmetry in question.
In 1951, he struck with Robert Pound an experiment to generate negative temperatures (over a population inversion ). This proposal influenced the ideas of Charles Townes to the development of the maser.
He received in 1952 along with Felix Bloch for his work on NMR the Nobel Prize for physics. In 1967 he was awarded the Oersted Medal. In 1984 he received the Max Delbruck Prize in Biophysics.
Works
- EM Purcell, HC Torrey and RV Pound: Resonance absorption by nuclear magnetic moments in a solid. In: Physical Review. Volume 69, 1946, p 37
- Electricity and magnetism. 4th Edition, Springer Verlag, 1989, Berkeley Physics Course Volume 2, ISBN 3-540-41571-8