David E. Pritchard

For his thesis he built the first atomic scattering machine with polarized atoms to study differential spin exchange scattering - the process that excites the 21 cm hydrogen radiation used to map our galaxy. Pritchard was a pioneer in the application of tunable lasers to physics and chemistry, being the first to demonstrate high resolution spectroscopy when two laser photons are absorbed simultaneously. He used both laser and RF spectroscopy to study weakly bound van der Waals molecules like NaNe (BLP77) and KAr (MPK74) made in cold supersonic molecular beams.

Exploiting the ability of tunable lasers to transfer large amounts of momentum to atoms, Pritchard performed classic demonstrations of the diffraction of atoms from a standing wave of light (denoted Kapitza-Dirac or Raman-Nath regimes) and Bragg Scattering (MOM88) of atoms from light gratings, founding the field of coherent atom optics (WPW99). This led to the first atom interferometer (KET91) where the atom wave passed on both sides of a metal foil before recombining, so that different interactions on the two sides produced a fringe shift of the atomic interference pattern (ESC95). This allowed precise measurements of atomic polarizability, the index of refraction of gasses for atom waves, and fundamental tests of quantum decoherence, as well as the first demonstration of the power of atom interferometers to measure rotation like a gyroscope and to work for complex particles like Na₂ molecules (CSP09).

A singularly important development from atom optics is Pritchard’s invention of the magneto-optical trap (PRB86) that captures and cools atoms to sub-milliKelvin temperatures and the “dark spot MOT” (with postdoc Wolfgang Ketterle, KDJ93) that can compress ~ 10¹⁰ cold atoms in the same small volume. Together with a magnetic atom trap Pritchard independently re-invented (sometimes called the Ioffe-Pritchard trap to honor its plasma physics origin), These traps are the workhorses in the field of cold atom research and are the foundational tools for the MIT-Harvard Center for Ultracold Atoms.

In 1990, he brought Wolfgang Ketterle to MIT as a postdoctoral researcher to work on atom cooling. To induce Wolfgang to stay at MIT, in 1993 he gave him his experimental cold atom program (with two students and two grants) and stepped aside from that 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, along with Pritchard’s former graduate student, Eric Cornell and Carl Wieman who was an informal Pritchard mentee as an undergraduate at MIT. Ketterle gave Pritchard his Nobel medal.

Ketterle and Pritchard then partnered to study atom optics and interferometry with Bose condensates, demonstrating coherent amplification of matter waves, superradiant Rayleigh scattering, the power of Bragg spectroscopy to probe the condensate, and even used laser light to establish coherence between two condensates that never touch.

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 (RTP04). 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 Einstein’s prediction that E = mc² – now at ½ part per million (RTM05).

Precise measurements of the masses of Rb and Cs made with the MIT apparatus have been combined with others’ high-precision atom interferometric measurements of h/m (Planck’s 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 a measurement based on quantum electrodynamics. This is the most precise comparison of measurements made using entirely different theoretical bases.

Pritchard has a life-long interest in teaching expertise in problem solving. In the 1970’s he authored _{Mechanics Workbook}, a programmed instruction manual for Newtonian mechanics. He has a large collection of puzzles and paradoxes in physics and has taught a 10-hour course many times during MIT’s January Independent Activities Period. He also collects “physics for lunch” problems, each one of which typically puzzles beginning graduate students for a lunch period.

In 1998, he and his son Alex developed an online Socratic tutor, mycybertutor.com, that offers specific critiques of incorrect symbolic answers as well as hints upon request and follow-up comments and questions. It increases students’ ability to answer traditional MIT examination problems by ~ 2 standard deviations(MoP09) and is now marketed as Mastering Physics.com, MasteringChemistry and …Astronomy by Pearson Education. It has been the dominant homework tutor in Science and Engineering for over a decade with ~ 2.5M users annually.

Pritchard’s education research group http://RELATE.MIT.edu was started in 2000 with a 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 (MoP09), and is the dominant contributor to ~ 5% of the certificates given by edX.org. Contrary to general opinion, RELATE showed that top and bottom cohorts learned equally in a MOOC (DDL14). They explored (CCP16) new types of instruction (e.g. deliberate practice of critical problem-solving skills) or variations in instruction (adding a diagram, replacing multiple choice questions by more interactive drag and drop questions, etc.) are compared with traditional instruction (the control). These experiments and others’ research point to a general need to help students learn a principal component of expertise: strategic thinking – the ability to determine which concepts and which procedures are helpful in solving an unfamiliar problem. For this purpose RELATE developed a Mechanics Reasoning Inventory (PBC11) that measures strategic ability; it served as a benchmark of progress for their new pedagogy, Modeling Approach to Problem Solving. This pedagogy greatly improved the expertise of students’ attitudes towards learning science, raised their scores on the Physics 1 final exam retake, (PBP09) and subsequently helped them improve their Physics 2 grade by ~ ½ std dev relative to students who didn’t benefit from this intervention (RPB10).

Throughout his career, Pritchard has excelled as a mentor and advisor. In addition to the three Nobel prizewinners mentioned above, a different four of Pritchard’s students, none of them yet Nobelists, have won national thesis awards. A disproportionate number of his mentees and students have positions in top-20 physics departments or top laboratories like NIST. Every alum of his education group stepped into a job in a university as an assistant professor or education-related position, or in an education company. His abilities as advisor and mentor were recognized at MIT by his appointment as the first physics major coordinator, and he has won the MIT Dean’s award for teaching and advising, the Earll M. Murman Award for Excellence in Undergraduate Advising, the Hertz Foundation Mentor’s Honorarium, and a “World's Best Mentor” award from Dowling College. He has been a director of a failed precast concrete company as well as the Optical Society of America, now Optika, and was founder of Effective Educational Technologies (sold to Pearson Education in 2006).

In his personal life, Pritchard and his wife of 55 years, Andrea, have extensively modified (including design, carpentry, plumbing, and electrical work) three houses. For relaxation they sail and race their 30’ classic sailboat. They have two sons and four grandchildren.

BLP77 Laser Spectroscopy of Bound NaNe Molecules, R. Ahmad Bitar, W. Lapatovich, and D. E. Pritchard, PRL 39, 1657 (1977)

CCL14 Learning in an Introductory Physics MOOC: All Cohorts Learn Equally, Including an On-­Campus Class Kimberly F Colvin, John Champaign, Alwina Liu, Qian Zhou, Colin Fredericks, and David E Pritchard Int. Rev. Research in Online and Distance Learning irrodl.org /index.php/irrodl/article/view/1902/3009

CCP16 Researching for better instructional methods using AB experiments in MOOCs: results and challenges Zhongzhou Chen, Christopher Chudzicki, Daniel Palumbo, Giora Alexandron, Youn-Jeng Choi, Qian Zhou, David E. Pritchard Research and Practice in Technology Enhanced Learning: December 2016, 11:9 DOI: 10.1186/s41039-016-0034-4 (Earlier work by Chudzicki et. al. Learning at Scale 2015 and Z Chen at EDM16)

CSP09 Optics and interferometry with atoms and molecules Cronin, Alexander D.; Schmiedmayer, Joerg; Pritchard, David E. Rev. Mod. Phys. 81, 1051–1129 (2009) , arXiv:0712.3703

ESC95 Measurement of the Electric Polarizability of Sodium with an Atom Interferometer, C. R. Ekstrom, J. Schmiedmayer, M. S. Chapman, T. D. Hammond, and D. E. Pritchard, PRA . 51, 3883 (1995)KDJ93 High-densities of cold atoms in a dark spontaneous-force optical trap, W. Ketterle, K.B. Davis, M.A. Joffe, A. Martin and D.E. Pritchard, PRL 70, 2253 (1993).

KET91 An Interferometer for Atoms, D. W. Keith, C.R. Ekstrom, Q.A. Turchette, and D.E. Pritchard, PRL. 66, 2693 (1991) MOM88 Bragg Scattering of Atoms from a Standing Light Wave, P.J. Martin, B.G. Oldaker, A.H. Miklich, and D.E. Pritchard, PRL. 60, 515 (1988)

MoP09 What course elements correlate with improvement on tests in introductory Newtonian mechanics?, Elsa-Sofia Morote and David E. Pritchard Am. J. Phys. 77, 746, (2009)

MPK74 Spin-Rotation Coupling in the Alkali-Rare Gas Molecule KAr, E. Mattison, D. E. Pritchard, and D. Kleppner, PRL 32, 507 (l974)

PBC11 Development of a Mechanics Reasoning Inventory Andrew Pawl, Analia Barrantes, Carolin Cardamone, Saif Rayyan and David E. Pritchard Physics Education Research Conference 2011 Volume 1413, Pages 287-290

PBP09 Modeling Applied to Problem Solving, Pawl, A., Barrantes, A. and Pritchard, D. E., AIP Conference Proceedings 1179 2009 Physics Education Research Conference, M. Sabella, Ch. Henderson, C. Singh, Eds. pp. 51-54, (2009)

PRB86 Light Traps Using Spontaneous Forces, D.E. Pritchard, E.L. Raab, V. Bagnato, C.E. Wieman, and R.N. Watts, PRL 57,310 (1986).

RPB10 Improved Student Performance In Electricity And Magnetism Following Prior MAPS Instruction In Mechanics, Rayyan, S., Pawl, A., Barrantes, A. , Teodorescu, R. and Pritchard, D. E., Physics Education Research Conference 2010 AIP Conf. Proc. 1289, 273(2010)

RTM05 World year of physics – A direct test of E=mc2, S. Rainville, J.K. Thompson, E.G. Myers, J.M. Brown, M.S. Dewey, E.G. Kessler, R.D. Deslattes, H.G. Borner, M. Jentschel, P. Mutti, D.E. Pritchard, Nature, 438, 1096-1097, (2005)

RTP04 An Ion Balance for Ultra-High-Precision Atomic Mass Measurement, Simon Rainville, James K. Thompson, David E. Pritchard, Science, 303, January 16, 2004, pages 334-338, www.sciencemag.org (manuscript number 1092320/issue date 01/16/2003).

WPW99 Atom Cooling, Trapping and Quantum Manipulation, C. E. Wieman, D. E. Pritchard and D. J. Wineland, special Centenary issue Rev. Mod. Phy. 71, S253-S262, March 1999

• David Pritchard appointed as Director of Research Laboratory of Electronics at MIT
• MIT'S Wolfgang Ketterle: New Marching Orders for Atoms