David E.

Pritchard
David Edward Pritchard (born October 15, 1941)[2]
is a professor at the Massachusetts Institute of David Edward Pritchard
Technology (MIT) who specializes in atomic physics Born October 15, 1941
and educational research. New York, U.S.
Alma mater California Institute of
Technology (MA)
Career Harvard University (PhD)
Scientific career
Fields Atomic physics
Early work
Institutions Massachusetts Institute of
Pritchard completed his PhD in 1968 at Harvard Technology
University under the supervision of Daniel Kleppner.
Thesis Differential Spin Exchange
His thesis involved building the first atomic scattering
Scattering: Sodium on
machine with polarized atoms to study differential spin Cesium.[1] (1968)
exchange scattering, a process by which the 21 cm
Doctoral Daniel Kleppner
hydrogen line manifests.[1]
advisor
Pritchard was an early adopter of tunable lasers in Doctoral Eric Cornell
physics and chemistry, demonstrating high-resolution students
spectroscopy through the simultaneous absorption of Other notable Jerome Apt (Astronaut)
two laser photons. He employed both laser and radio- students
frequency spectroscopy to study weakly bound van der
Website web.mit.edu/physics/people
Waals molecules, such as NaNe[3] and KAr,[4] in cold
/faculty/pritchard_david.html
supersonic molecular beams.
(https://web.mit.edu/physics/p
eople/faculty/pritchard_david.
Atom optics, atom traps, and atom html)

interferometers
Pritchard made use of tunable lasers' ability to transfer momentum to atoms, leading to demonstrations of
the diffraction of atoms from a standing wave of light (denoted Kapitza-Dirac or Raman-Nath regimes)
and Bragg scattering[5] of atoms from light gratings, founding the field of coherent atom optics.[6] This
led to the creation of the first atom interferometer,[7] where matter waves would propagate on both sides
of a metal foil before recombining, so that different interactions on the two sides would result in a fringe
shift of the atomic interference pattern.[8] This allowed for precise measurements of atomic polarizability,
the refractive index of gaseous matter waves, and fundamental testing of quantum decoherence, as well as
the first demonstration of the ability of atom interferometers to measure angular velocity like a gyroscope
and to work for complex particles like Na2 molecules in the gaseous phase.[9]

A singularly important development from atom optics is Pritchard's invention of the magneto-optical
trap[10] which captures and cools atoms to sub-millikelvin temperatures and of the Dark SPOT MOT, in
which atoms are confined in a way such that they do not interact with trapping light.[11] Together with a
magnetic atom trap, it can compress ~ 1010 cold atoms into the same small volume (This is sometimes
called the Ioffe-Pritchard trap to honor its plasma physics origin). These traps are commonly used in the
field of cold atom research and are the foundational tools for the MIT-Harvard Center for Ultracold
Atoms.

In 1990, Pritchard brought Wolfgang Ketterle to MIT as a postdoctoral researcher to work on atom
cooling. To encourage Ketterle to stay at MIT, in 1993 Ketterle was given his own experimental cold
atom program (with two students and two grants) while Pritchard himself stepped aside from the field to
allow Ketterle to be appointed to the faculty. Ketterle pursued atom cooling to achieve Bose–Einstein
condensation in 1995, a discovery for which Ketterle was awarded the Nobel Prize in Physics in 2001,
alongside Pritchard's former graduate student, Eric Allin Cornell, and Carl Wieman, who was an informal
Pritchard mentee while an undergraduate at MIT.[12]

Ketterle and Pritchard then partnered to study atom optics and interferometry with Bose condensates,
demonstrating coherent amplification of matter waves, superradiant Rayleigh scattering, and the power of
Bragg spectroscopy to probe the condensate and used laser light to establish coherence between two
condensates that never touch. Pritchard received the 2004 Max Born Award, "For creative application of
light to new forms of spectroscopy, to manipulation and trapping of atoms, and for pioneering the new
fields of atom optics and atom interferometry".[13]

Precise measurements of atomic masses

Pritchard is a pioneer in the precise measurement of atomic and molecular masses using ion traps, an
advance enabled by his group's developing highly sensitive radio-frequency detectors based on SQUIDs
(superconducting quantum interference devices) and techniques to coherently cross-couple the motion of
different modes of an ion's oscillation in the trap. These advances culminated in an ion balance in which
one each of two different ions were simultaneously confined while their cyclotron frequencies were inter-
compared to better than one part in 1011.[14] This led to the discovery of a new type of systematic shift of
the cyclotron frequency due to the polarizability of the ion, providing the most accurate measurement of
ionic molecule polarizability. It also resulted in a fifty-fold improvement of experimental tests of Albert
Einstein's mass–energy equivalence that (where E is the energy, m is the mass and c the speed
of light) – now at ½ part per million. [15]

Precise measurements of the masses of rubidium and caesium (Cesium) atoms made with the MIT
apparatus have been combined with others' high-precision atom interferometric measurements of h/m (the
Planck constant divided by the atom mass) to give the most accurate value of the fine structure constant at
0.2 ppb (parts per billion), differing by ~ 2.5 combined errors from measurement based on quantum
electrodynamics. This is the most precise comparison of measurements made using entirely different
theoretical bases.

Teaching and education software

In 1998, David Pritchard and his son Alex developed an online Socratic tutor, mycybertutor.com, which
provides specific critiques of incorrect symbolic answers, hints upon request, and follow-up comments
and questions. This tool has been shown to significantly improve students' ability to answer traditional
MIT examination problems, increasing their performance by approximately 2 standard deviations.[16] The
software is now marketed as Mastering Physics, Mastering Chemistry, and Mastering Astronomy by
Pearson Education. It has become a widely used homework tutor in Science and Engineering, with
approximately 2.5 million.

Pritchard's education research group, RELATE[17] was started in 2000 with the goal to "Apply the
principles and techniques of science and engineering to study and improve learning, especially of
expertise". They conduct research using all components in the acronym RELATE - Research in Learning,
Assessing, and Tutoring Effectively. They showed that copying online homework is by far the best
predictor of a low final exam grade in MIT residential physics,[16] and is the dominant contributor to ~
5% of the certificates given by edX. They explored new types of instruction (e.g. deliberate practice of
critical problem-solving skills) or variations in instruction (adding a diagram, replacing multiple choice
questions with more interactive drag and drop questions, etc.) compared with traditional instruction (the
control).[18][19]

These experiments, along with other relevant research, indicated an important principle that students were
struggling with – strategic thinking – the ability to determine which concepts and procedures are helpful
in solving an unfamiliar problem. For this purpose, RELATE developed a Mechanics Reasoning
Inventory[20] that measures strategic ability; it served as a benchmark of progress for their new pedagogy:
Modeling Approach to Problem-Solving. This pedagogy was shown to greatly improve students' attitudes
towards learning science, raise their scores on the Physics 1 final exam retake,[21] and subsequently help
1
them improve their Physics 2 grade by ~ ⁠2 ⁠standard deviation relative to students who didn't benefit from
this intervention.[22]

References
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ttps://www.physics.harvard.edu/uploads/files/thesesPDF/PhD1954-1970.pdf) (PDF).
Harvard University Department of Physics. Archived from the original (https://www.physics.h
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26 July 2019.
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26). "Laser Spectroscopy of Bound NaNe Molecules" (https://link.aps.org/doi/10.1103/Phys
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 5. Martin, Peter J.; Oldaker, Bruce G.; Miklich, Andrew H.; Pritchard, David E. (1988-02-08).
"Bragg scattering of atoms from a standing light wave" (https://link.aps.org/doi/10.1103/Phys
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trapping, and quantum manipulation" (https://link.aps.org/doi/10.1103/RevModPhys.71.S25
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(https://doi.org/10.1103%2FRevModPhys.71.S253).
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05-27). "An interferometer for atoms" (https://dx.doi.org/10.1103/physrevlett.66.2693).
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8. Ekstrom, Christopher R.; Schmiedmayer, Jörg; Chapman, Michael S.; Hammond, Troy D.;
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10. Pritchard, D. E.; Raab, E. L.; Bagnato, V.; Wieman, C. E.; Watts, R. N. (1986-07-21). "Light
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11. Ketterle, Wolfgang; Davis, Kendall B.; Joffe, Michael A.; Martin, Alex; Pritchard, David E.
(1993-04-12). "High densities of cold atoms in adarkspontaneous-force optical trap" (https://
dx.doi.org/10.1103/physrevlett.70.2253). Physical Review Letters. 70 (15): 2253–2256.
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Institute of Technology. 2004-06-02. Retrieved 2024-09-18.
14. Rainville, Simon; Thompson, James K.; Pritchard, David E. (2004-01-16). "An Ion Balance
for Ultra-High-Precision Atomic Mass Measurements" (https://doi.org/10.1126%2Fscience.1
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PMID 14671311 (https://pubmed.ncbi.nlm.nih.gov/14671311). S2CID 10927619 (https://api.
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15. Rainville, Simon; Thompson, James K.; Myers, Edmund G.; Brown, John M.; Dewey,
Maynard S.; Kessler, Ernest G.; Deslattes, Richard D.; Börner, Hans G.; Jentschel, Michael;
Mutti, Paolo; Pritchard, David E. (2005). "A direct test of E=mc2" (https://dx.doi.org/10.1038/
4381096a). Nature. 438 (7071): 1096–1097. doi:10.1038/4381096a (https://doi.org/10.103
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16. Morote, Elsa-Sofia; Pritchard, David E. (2009-08-01). "What course elements correlate with
improvement on tests in introductory Newtonian mechanics?" (https://dx.doi.org/10.1119/1.3
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Jeng; Zhou, Qian; Pritchard, David E. (2016). "Researching for better instructional methods
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c/articles/PMC6302917). Research and Practice in Technology Enhanced Learning. 11 (1):
9. doi:10.1186/s41039-016-0034-4 (https://doi.org/10.1186%2Fs41039-016-0034-4).
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20. Pawl, Andrew; Barrantes, Analia; Cardamone, Carolin; Rayyan, Saif; Pritchard, David E.;
Rebello, N. Sanjay; Engelhardt, Paula V.; Singh, Chandralekha (2012). "Development of a
mechanics reasoning inventory" (https://dx.doi.org/10.1063/1.3680051). AIP Conference
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3680051). hdl:1721.1/78556 (https://hdl.handle.net/1721.1%2F78556).
21. Pawl, Andrew; Barrantes, Analia; Pritchard, David E.; Sabella, Mel; Henderson, Charles;
Singh, Chandralekha (2009). "Modeling Applied to Problem Solving" (https://dx.doi.org/10.1
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dl.handle.net/1721.1%2F76354).
22. Rayyan, Saif; Pawl, Andrew; Barrantes, Analia; Teodorescu, Raluca; Pritchard, David E.;
Singh, Chandralekha; Sabella, Mel; Rebello, Sanjay (2010). "Improved Student
Performance In Electricity And Magnetism Following Prior MAPS Instruction In Mechanics"
(https://dx.doi.org/10.1063/1.3515221). AIP Conference Proceedings. 1289 (1). AIP: 273–
276. Bibcode:2010AIPC.1289..273R (https://ui.adsabs.harvard.edu/abs/2010AIPC.1289..27
3R). doi:10.1063/1.3515221 (https://doi.org/10.1063%2F1.3515221). hdl:1721.1/63094 (http
s://hdl.handle.net/1721.1%2F63094).

External links
David Pritchard appointed as Director of Research Laboratory of Electronics at MIT (https://
web.archive.org/web/20060912110646/http://www.rle.mit.edu/news/news_07012003.html)
MIT'S Wolfgang Ketterle: New Marching Orders for Atoms (http://www.sciencewatch.com/ja
n-feb99/sw_jan-feb99_page3.htm)

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