Outdoing Maxwell’s Demon: Taming Molecular Wildness

By Dudley R. Herschbach

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA

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In 1867, James Clerk Maxwell imagined a tiny demon capable of sorting fast from slow molecules. That capability and much more has been achieved by molecular beam and laser techniques. This talk describes these developments, illustrating means to analyze and control molecular trajectories and spatial orientation and to select rotational and vibrational states, with applications to elucidating chemical reaction dynamics. Also discussed are means to “trap” molecules, confining their translational motion and cooling them to ultracold temperatures (< 1 mK) while still in the gas phase. Such ultracold molecules will move like lazy beetles rather than chaotic bullets, thus acquiring deBroglie wavelengths longer than their size or separation. In prospect, this gives access to an exotic realm of “hyperquantum” collision dynamics, with chemical reactivity governed by resonances and tunneling processes. Another exotic realm now in prospect is quantum computing, using ultracold polar molecules trapped in an optical lattice (the subject of the Theoretical Chemistry Lecture tomorrow).


Dudley Herschbach Third-generation native of San Jose, California. Grew up near Cupertino, in what was then rural area; for years milked cows, fed chickens and pigs, picked prunes, apricots, and walnuts in summers. First in his family to attend college, recruited as a football player. Earned B.S. in math and M.S. in chemistry at Stanford, mentored by George Polya and Harold Johnston; A.M. in physics and Ph.D. in chemical physics from Harvard, mentored by E. Bright Wilson. Appointed assistant professor of chemistry at U.C. Berkeley in 1959, undertook experiments to probe reaction dynamics of molecules in single collisions. Returned to Harvard in 1963. With Yuan Lee and John Polanyi, shared Nobel Prize in 1986. Taught graduate courses in quantum mechanics, molecular spectroscopy, and collision theory; undergrad courses in physical chemistry and for twenty years freshman chemistry.

Emeritus at Harvard since 2002, have continued since to teach freshman seminar (“Molecular Motors: Wizards of the Nanoworld”) there; also have visiting appointments in physics and astronomy at Texas A & M University and at the geophysical laboratory at the Carnegie Institution of Washington. Current research topics: pursuing an unorthodox dimensional scaling approach to electronic structure; elucidating interaction of molecules with superintense laser fields; analysis of wave function entanglement that pertains to proposed quantum computers; experiments striving to produce very slow, cold molecular beams which act like waves.

Efforts to enhance science education and public understanding have centered for 20 years on the Society for Science and the Public, which publishes Science News and conducts the Intel Science Talent Search and the Intel International Science and Engineering Fair. Have had many radio and TV appearances, including as a guest voice on The Simpsons. Also a life member of Friends of Franklin and of the Sierra Club, and for many years chaired the Hans Bethe Center for Arms Control and Nonproliferation.

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Purdue Physical Chemistry Seminar Series

Cite this work

Researchers should cite this work as follows:

  • Dudley R. Herschbach (2011), "Outdoing Maxwell’s Demon: Taming Molecular Wildness," http://nanohub.org/resources/11192.

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WTHR 201, Purdue University, West Lafayette, IN