Edward Mills Purcell

Edward Mills Purcell (August 30, 1912 – March 7, 1997) was an American physicist who shared the 1952 Nobel Prize for Physics for his independent discovery (published 1946) of nuclear magnetic resonance in liquids and in solids.[2] Nuclear magnetic resonance (NMR) has become widely used to study the molecular structure of pure materials and the composition of mixtures.

Edward Mills Purcell
Edward Mills Purcell
Edward Mills Purcell (1912–1997)
BornAugust 30, 1912
Taylorville, Illinois, United States
DiedMarch 7, 1997 (aged 84)
NationalityUnited States
Alma materPurdue University (BSEE)
Harvard University (M.A.)
Harvard University (Ph.D)
Known forNuclear magnetic resonance (NMR)
Smith-Purcell effect
21 cm line
Scallop theorem
AwardsNobel Prize for Physics (1952)
Oersted Medal (1967)
National Medal of Science (1979)
Max Delbruck Prize (1984)
Beatrice M. Tinsley Prize (1988)
Scientific career
FieldsPhysics
InstitutionsHarvard University
MIT
Doctoral advisorKenneth Bainbridge
Other academic advisorsJohn Van Vleck
Doctoral studentsGeorge Pake
George Benedek
Charles Pence Slichter
Other notable studentsNicolaas Bloembergen
Green Banks - Ewen-Purcell Horn Antenna
Horn antenna used by Harold I. Ewen and Edward M. Purcell at the Lyman Laboratory of Physics at Harvard University in 1951 for the first detection of radio radiation from nuclear atomic hydrogen gas in the Milky Way at a wavelength of 21 cm. Now at National Radio Astronomy Observatory in Green Bank, WV.[1]

Biography

Born and raised in Taylorville, Illinois, Purcell received his BSEE in electrical engineering from Purdue University, followed by his M.A. and Ph.D. in physics from Harvard University. He was a member of the Alpha Xi chapter of the Phi Kappa Sigma Fraternity while at Purdue.[3] After spending the years of World War II working at the MIT Radiation Laboratory on the development of microwave radar, Purcell returned to Harvard to do research. In December 1946, he discovered nuclear magnetic resonance (NMR) with his colleagues Robert Pound and Henry Torrey.[4] NMR provides scientists with an elegant and precise way of determining chemical structure and properties of materials, and is widely used in physics and chemistry. It also is the basis of magnetic resonance imaging (MRI), one of the most important medical advances of the 20th century. For his discovery of NMR, Purcell shared the 1952 Nobel Prize in physics with Felix Bloch of Stanford University.

Purcell also made contributions to astronomy as the first to detect radio emissions from neutral galactic hydrogen (the famous 21 cm line due to hyperfine splitting), affording the first views of the spiral arms of the Milky Way.[5] This observation helped launch the field of radio astronomy, and measurements of the 21 cm line are still an important technique in modern astronomy. He has also made seminal contributions to solid state physics, with studies of spin-echo relaxation, nuclear magnetic relaxation, and negative spin temperature (important in the development of the laser). With Norman F. Ramsey, he was the first to question the CP symmetry of particle physics.

Purcell was the recipient of many awards for his scientific, educational, and civic work. He served as science advisor to Presidents Dwight D. Eisenhower, John F. Kennedy, and Lyndon B. Johnson. He was president of the American Physical Society, and a member of the American Philosophical Society, the National Academy of Sciences, and the American Academy of Arts and Sciences. He was awarded the National Medal of Science in 1979, and the Jansky Lectureship before the National Radio Astronomy Observatory. Purcell was also inducted into his Fraternity's (Phi Kappa Sigma) Hall of Fame as the first Phi Kap ever to receive a Nobel Prize.

Purcell was the author of the innovative introductory text Electricity and Magnetism.[6] The book, a Sputnik-era project funded by an NSF grant, was influential for its use of relativity in the presentation of the subject at this level. The 1965 edition, now freely available due to a condition of the federal grant, was originally published as a volume of the Berkeley Physics Course. Half a century later, the book is also in print as a commercial third edition, as Purcell and Morin. Purcell is also remembered by biologists for his famous lecture "Life at Low Reynolds Number",[7] in which he explained a principle referred to as the Scallop theorem.

See also

References

  1. ^ "E. M. Purcell - Biography". The Nobel Prize in Physics 1952 Felix Bloch, E. M. Purcell. The Nobel Foundation. 1952. Retrieved 22 May 2012.
  2. ^ Bleaney, B. (1999). "Edward Mills Purcell. 30 August 1912 -- 7 March 1997: Elected For.Mem.R.S. 1989". Biographical Memoirs of Fellows of the Royal Society. 45: 437–447. doi:10.1098/rsbm.1999.0029.
  3. ^ "Famous Phi Kappa Sigma's - Famous Fraternity & Sorority Greeks - Greek 101". greek101.com.
  4. ^ Purcell, E.; Torrey, H.; Pound, R. (1946). "Resonance Absorption by Nuclear Magnetic Moments in a Solid". Physical Review. 69: 37. Bibcode:1946PhRv...69...37P. doi:10.1103/PhysRev.69.37.
  5. ^ Ewen, H. I.; Purcell, E. M. (1951). "Observation of a Line in the Galactic Radio Spectrum: Radiation from Galactic Hydrogen at 1,420 Mc./sec". Nature. 168 (4270): 356. Bibcode:1951Natur.168..356E. doi:10.1038/168356a0.
  6. ^ "Electricity and Magnetism". google.com.
  7. ^ Purcell, E. M. (1977). "Life at low Reynolds number". American Journal of Physics. 45: 3–11. Bibcode:1977AmJPh..45....3P. doi:10.1119/1.10903.

External links

1912

1912 (MCMXII)

was a leap year starting on Monday of the Gregorian calendar and a leap year starting on Sunday of the Julian calendar, the 1912th year of the Common Era (CE) and Anno Domini (AD) designations, the 912th year of the 2nd millennium, the 12th year of the 20th century, and the 3rd year of the 1910s decade. As of the start of 1912, the Gregorian calendar was

13 days ahead of the Julian calendar, which remained in localized use until 1923.

A key event of this year was the sinking of the infamous RMS Titanic

1952 in science

The year 1952 in science and technology involved some significant events, listed below.

1997 in science

The year 1997 in science and technology involved many significant events, listed below.

Edward Purcell

Edward Purcell may refer to:

Edward A. Purcell Jr., American historian

Edward Henry Purcell (died 1765), English organist, printer, and music publisher

Edward Mills Purcell (1912–1997), American physicist, Nobel Prize winner

Edward Purcell (musician) (1689–1740), English composer

Edward Purcell (rugby league) (born 1988), Samoan rugby league international

Teddy Purcell (Edward Purcell, born 1985), Canadian ice hockey player

Felix Bloch

Felix Bloch (23 October 1905 – 10 September 1983) was a Swiss-American physicist and Nobel physics laureate who worked mainly in the U.S. He and Edward Mills Purcell were awarded the 1952 Nobel Prize for Physics for "their development of new ways and methods for nuclear magnetic precision measurements." In 1954–1955, he served for one year as the first Director-General of CERN. Felix Bloch made fundamental theoretical contributions to the understanding of electron behavior in crystal lattices, ferromagnetism, and nuclear magnetic resonance.

George Pake

George E. Pake (April 1, 1924 – March 4, 2004) was a physicist and research executive primarily known for helping found Xerox PARC.

Harrison M. Randall

Harrison McAllister Randall (December 17, 1870 – November 10, 1969) was an American physicist whose leadership from 1915 to 1941 brought the University of Michigan to international prominence in experimental and theoretical physics.

John Hasbrouck Van Vleck

John Hasbrouck Van Vleck (March 13, 1899 – October 27, 1980) was an American physicist and mathematician. He was co-awarded the Nobel Prize in Physics in 1977, for his contributions to the understanding of the behavior of electrons in magnetic solids.

John Torrence Tate Sr.

John Torrence Tate Sr. (July 28, 1889 – May 27, 1950) was an American physicist noted for his editorship of Physical Review between 1926 and 1950. He is the father of mathematician John Torrence Tate Jr.

List of Fellows of the Royal Society elected in 1989

Fellows of the Royal Society elected in 1989.

March 7

March 7 is the 66th day of the year (67th in leap years) in the Gregorian calendar. 299 days remain until the end of the year.

Nicolaas Bloembergen

Nicolaas "Nico" Bloembergen (March 11, 1920 – September 5, 2017) was a Dutch-American physicist and Nobel laureate, recognized for his work in developing driving principles behind nonlinear optics for laser spectroscopy. During his career, he was a professor at both Harvard University and later at the University of Arizona.

Bloembergen shared the 1981 Nobel Prize in Physics with Arthur Schawlow, along with Kai Siegbahn for his laser spectroscopy work.

Phi Kappa Sigma

Phi Kappa Sigma (ΦΚΣ) is an international all-male college secret and social fraternity. While nicknames differ from institution to institution, the most common nicknames for the fraternity are Skulls, Skullhouse, Phi Kap, and PKS (the first two because of the skull and crossbones on the fraternity's badge and coat of arms). Phi Kappa Sigma was founded by Dr. Samuel Brown Wylie Mitchell at the University of Pennsylvania. Mitchell recorded the initial ideas and concepts of Phi Kappa Sigma on August 16, 1850. He then began to discuss the idea with other students, first Charles Hare Hutchinson, and then Alfred Victor du Pont (son of Alfred V. du Pont), John Thorne Stone, Andrew Adams Ripka, James Bayard Hodge, and Duane Williams. The seven men formally founded the fraternity on October 19, 1850 becoming the founding fathers of Phi Kappa Sigma Phi Kappa Sigma is a charter member of the North-American Interfraternity Conference, and since 2017, is headquartered in Carmel, Indiana. Prior to that, starting with its founding in 1850, the fraternity was based out of Philadelphia, Valley Forge and Chester Springs, Pennsylvania.

Purcell (surname)

Purcell is a surname of Norman origin, and common in Ireland and England. It was given to those whose occupation was swineherd.

Purcell effect

The Purcell effect is the enhancement of a quantum system's spontaneous emission rate by its environment. In the 1940s Edward Mills Purcell discovered the enhancement of spontaneous emission rates of atoms when they are incorporated into a resonant cavity (the Purcell Effect). The magnitude of the enhancement is given by the Purcell factor

where is the wavelength within the cavity material of refractive index , and and are the quality factor and mode volume of the cavity, respectively.

One way of seeing why this enhancement arises is by using cavity quantum electrodynamics. Fermi's golden rule dictates that the transition rate for the atom-vacuum (or atom-cavity) system is proportional to the density of final states. In a cavity at resonance, the density of final states is enhanced (though the number of final states may not be). The Purcell factor is then just the ratio of the cavity

to that of the free space density of states

Using

we get that

which is correct up to a constant.

It has been predicted theoretically that a 'photonic' material environment can control the rate of radiative recombination of an embedded light source. A main research goal is the achievement of a material with a complete photonic bandgap: a range of frequencies in which no electromagnetic modes exist and all propagation directions are forbidden. At the frequencies of the photonic bandgap, spontaneous emission of light is completely inhibited. Fabrication of a material with a complete photonic bandgap is a huge scientific challenge. For this reason photonic materials are being extensively studied. Many different kinds of systems in which the rate of spontaneous emission is modified by the environment are reported, including cavities, two, and three-dimensional photonic bandgap materials.

The Purcell effect can also be useful for modeling single-photon sources for quantum cryptography. Controlling the rate of spontaneous emission and thus raising the photon generation efficiency is a key requirement for quantum dot based single-photon sources.

Scallop theorem

The Scallop theorem states that to achieve propulsion at low Reynolds number in Newtonian fluids a swimmer must deform in a way that is not invariant under time-reversal. Edward Mills Purcell stated this theorem in his 1977 paper Life at Low Reynolds Number explaining physical principles of aquatic locomotion. The theorem is named for the motion of a scallop - an opening and closing of a simple hinge - which is not sufficient to create migration at low Reynolds numbers.

Although the movement of animal cells is usually studied as they migrate, it seems likely that many motile cells can also swim. Thus, human granulocytes are able to migrate towards a source of a chemoattractant, the tripeptide FMLP, whilst suspended in a uniformly-dense (isodense) medium. They swim at the same speed as they would crawl on a solid surface. Likewise, Dictyostelium discoideum amoebae swim towards a chemical attractant, in this case cyclic AMP. The actual mechanism that these neutrophils or amoebae use to produce a thrust against the medium to propel themselves is uncertain; however, how they do so must be consistent with physical principles. To swim they must transmit a force against the viscous fluid in order to propel themselves forward. Different mechanisms by which they might do so were presented by Ed Purcell in a famous talk he gave celebrating the 80th birthday of his friend Viki Weisskopf.

In this he developed his “scallop theorem”: a normal scallop moves by opening its shells slowly and shutting them quickly. In the latter step it quickly squeezes the fluid between the shells backwards and, using the momentum of the water, pushes itself forward. Purcell realised that a microorganism trying to do the same would simply move forwards on shutting its shells and move backwards to its original position on opening them. The set of movements is “reciprocal”: it appears the same if viewed forwards or backwards in time. He concluded that microorganisms cannot move by a reciprocal mechanism: to move, they must exert some thrust against the medium and do so in a non-reciprocal manner. He suggested various ways in which an organism could swim:

They could do so with a flagellum, which rotates, pushing the medium backwards — and the cell forwards — in much the same way that a ship’s screw moves a ship. This is how some bacteria move; the flagellum is attached at one end to a complex rotating motor held rigidly in the bacterial cell surface

They could use a flexible arm: this could be done in many different ways. For example, mammalian sperm have a flagellum which, whip-like, wriggles at the end of the cell, pushing the cell forward. Cilia are quite similar structures to mammalian flagella; they can advance a cell like paramecium by a complex motion not dissimilar to breast stroke.

A hypothetical toroidal cell could move by rotating its surface through the central hole, thereby creating a surface flow. The surface drag on the outer edges of the cell could provide the thrust against the medium needed to move the cell forward. This is related to the membrane flow model B of cell migration, except in that scheme the surface flow is achieved by removing surface from the rearward end of the cell and transporting it as vesicles through the cell interior to the cell's front.The manner in which cells swim, and therefore move, suggests that it is membrane flow which is the motor for movement.

Scientific Advisory Group

The Scientific Advisory Group of the United States Air Force, later renamed the Scientific Advisory Board, was established in 1944, when General Henry H. Arnold asked Dr. Theodore von Kármán to establish a group of scientists to review the techniques and research trends in aeronautics. The group was asked to evaluate the aeronautical research and development programs and facilities of the Axis powers of World War II, and to provide recommendations for future United States Air Force research and development programs.

Von Kármán picked the following scientists for initial members of the group: Hugh Dryden, Frank Wattendorf, Hsue-shen Tsien, T.F. Walkowitz, George S. Schairer, G.E. Valley, Ivan A. Getting, Edward Mills Purcell, Vladimir K. Zworykin, Lee DuBridge, and Norman Ramsey.Under von Kármán the group put together several reports for General Arnold, including, "Where We Stand" and "Toward New Horizons." General Arnold's vision and Dr. von Kármán's reports led to American airpower dominance and the establishment of the Air Engineering Development Center later renamed and dedicated as the Arnold Engineering Development Center (AEDC) in 1951.

Taylorville, Illinois

Taylorville is a city in and the county seat of Christian County, Illinois, United States. The population was 11,427 at the 2000 census, making it the county's largest city.

Yevgeny Zavoisky

Yevgeny Konstantinovich Zavoisky (Russian: Евгений Константинович Завойский; September 28, 1907 – October 9, 1976) was a Soviet physicist known for discovery of electron paramagnetic resonance in 1944. He likely observed nuclear magnetic resonance in 1941, well before Felix Bloch and Edward Mills Purcell, but dismissed the results as not reproducible. Zavoisky is also credited with design of luminescence camera for detection of nuclear processes in 1952 and discovery of magneto-acoustic resonance in plasma in 1958.

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