Kevin M. Jones

The William Edward McElfresh

Professor of Physics

at Williams since 1984

Prof. Jones (seated) with Dave Ticehurst '04 (at board), and Jeff Garland '03

during a tutorial meeting for Physics 405T Electromagnetic Theory. They are discussing

the propagation of light in optical fibers.

(photo from a Chronicle of Higher Education article about the Williams Tutorial Program).


  • Williams College: B.A., 1977
  • Stanford University: Ph.D., 1983
  • Fellow of the American Physical Society, 2008
  • Guest researcher: National Institute of Standards and Technology, Lawrence Livermore National Lab
  • Department Chair: 1992 - 2003, 2005- 2007

Contact Information:

  • Office: BSC 126
  • Lab: BSC 024
  • Phone: (413) 597-2123
  • Dept. Office: (413) 597-2482
  • Fax: (413) 597-4116
  • E-mail:

Courses taught recently or often


Research interests

I use lasers to study simple atoms and molecules. My research is conducted at the National Institute of Standards and Technology in Gaithersburg, MD in collaboration with Dr. Paul Lett, Dr. William Phillips and many others. One example:

Purely Long Range States in Diatomic Molecules

By shining a properly tuned laser on a dilute gas of atoms in a non-uniform magnetic field it is possible to produce "ultra-low" temperatures of less than 1 mK (i.e. 1/1000 of a degree above absolute zero). When two of these atoms collide, in the presence of light at just the right frequency, they can "photoassociate" to form a molecule. Because the cold atoms have very low velocities they tend to form molecules where the atoms are moving very slowly, i.e. at large internuclear distances. Molecular potentials at large range are determined by van der Waals-type long range forces which reflect atomic properties without the complication of electron cloud overlap. For most molecular states, the atoms will travel into smaller internuclear distance where electron cloud overlap does become important. However, there are some "purely long range" states where the two atoms vibrate back and forth but stay so far apart that only atomic properties and long range forces are important. Although such states were first predicted in 1977, it was not until the development of laser cooling that detailed spectroscopy has become possible.
Working with the laser cooling group at NIST, I have investigated one of these purely long range states in Na2 with the motivation of extracting a precise ATOMIC lifetime from the spectroscopy of the molecule. One interesting -- and unexpected -- result was that to understand the binding energy of this state it is necessary to include the "retardation" of the atom-atom interaction, that is the modification of the force between the two atoms due to the time it takes light to travel across the molecule (even though the two atoms are only about 3.5 nm ( = 10-17 light seconds) apart!).

This figure shows several rotational levels in the lowest vibrational state of the purely long range zero-g-minus (3/2) state of Na2. The arrows indicate the fitted line positions (where the lines would appear if the atoms were at a temperature of absolute-zero instead of at 450 micoKelvin).



A zoom-in on the largest line shown in the first figure. The red curve shows where the line would appear if we could somehow crank up the speed of light to infinity. The shift between the actual line position and the red curve is a result of the non-zero time it takes light to cross the molecule -- about 10-17 seconds.

Other Projects
(please see the publication list for names of the many collaborators involved in these projects)
  • Photoassociation can also be seen as a way of producing a sample of cold molecules in a well defined energy state, something which is difficult to do otherwise. With the NIST group, and colleagues from the University of Utrecht in Holland, I have used photoassociation to look at autoionizing, doubly-excited states of Na2.
  • We have done precision spectroscopy of the triplet ground state of Na2. Combining our measurements with precise work by E. Tiemann's group at Hannover we can pin down the two ground state potentials (singlet and triplet) to unprecedented precision. This information is useful for understanding the properties of Bose-Einstein condensates and for designing quantum computers based on controlled collisions of neutral atoms in an optical lattice.
  • We have shown that it is possible to produce cold sodium molecules in very high levels of the triplet ground electronic state.
  • As a senior honors project Ginel Hill '00 studied the hyperfine structure of one particular electronic state of Na2(the 1g 3S+3P3/2 state). Ginel showed that it is possible to experimentally label individual hyperfine lines as having either even or odd total nuclear spin. The observed hyperfine structure is well described by a relatively simple model.
  • We have used picosecond lasers to observe the dynamics of collisions between cold atoms.
  • We have observed "optically induced Feshbach resonances." When atoms collide in the presence of appropriately tuned light, their collisional properties are modified. Several such mechanisms have been investigated, the particular one we have observed relies on quantum mechanical interference between two pathways and this is analogous to the interference observed in a Michelson interferometer. Optical Feshbach resonances have been proposed as a way to modify the interactions in a Bose condensate. Our observation of such resonances in atoms at 1 mK is a first step towards exploring that possibility.
  • We have demonstrated an "all optical" route to the production of a Bose condensate of sodium atoms. The picture below shows two pairs of crossed laser beams from a 100 Watt fiber laser. The images are taken in yellow light that is strongly absorbed by sodium atoms trapped in the beams. An intial sample of cold atoms at about 300 microKelvin was produced in a magnetooptical trap. The laser beams were turned on to produce the optical traps, all of which are inside the MOT cloud. The MOT was turned off in just the right way to cool the atoms further and maximize the number loaded into the optical traps. In frame "a" the atoms have just been loaded into the optical traps and all of the untrapped atoms have fallen away. We used a photoassocation transition to optimize the trap loading process. Frame "b" is taken about 12 seconds later. During the time between frames the intensity of the laser forming the traps has been slowly lowered allowing the "hottest" atoms to evaporate thereby cooling the sample. Eventually the sample is cold and dense enough that the atoms undergo a transition to form a Bose condensate (or in this case, four Bose condensates).
  • A new project, not yet involving cold atoms, is the production of twin beams of light from four wave mixing in a Rb vapor. In the course of this work we found some interesting diffraction patterns due to the non-linear interaction between two crossed laser beams. Aubryn Murray '05 and Rachel Gealy '04 have investigated these. With Colin McCormack '95, a post-doc at NIST, we have started to study pulse propogation in the non-linear medium. Kristen Lemons '08 assisted in this work during the summer of 2006 and 2007. Work on this project has contiinued apace, see recent publications below (until such time as this web page is properly updated).

Review Article

  • Kevin M. Jones, Eite Tiesinga, Paul D. Lett and Paul S. Julienne, "Ultracold photoassociation spectroscopy: Long-range molecules and atomic scattering," Rev. Mod. Phys. 78, 483 (2006)


  • Kevin M. Jones and Jefferson Strait (compilers and contributers), "Optics and Spectroscopy Undergraduate Laboratory Resource Book," Optical Society of America, Washington DC (1993) ISBN 1-55752-270-7

Selected publications

  • A.J. Taylor, K.M. Jones, and A.L. Schawlow, "Scanning Pulsed Polarization Spectrometer Applied to Na2," J. Opt. Soc. Am. 73, 994 (1983).
  • K.P. Ziock, R.H. Howell, F. Magnota, R.A. Failor and K.M. Jones, "First Observation of Resonant Excitation of High-n States in Positronium," Phys. Rev. Lett. 64, 2366 (1990).
  • C. Gerz, T. W. Hodapp, P. Jessen, K. M. Jones, W. D. Phillips, C. I. Westbrook, and K. Molmer, "The Temperature of Optical Molasses for Two Different Atomic Angular Momenta," Europhys. Lett. 21, 661 (1993).
  • K. M. Jones, S. Maleki, S. Bize, P.D. Lett, C.J. Williams, H. Richling, H. Knockel, E. Tiemann, H. Wang, P.L. Gould and W.C. Stwalley, "Direct Measurement of the Ground-State Dissociation Energy in Na2," Phys. Rev. A 54 (2), R1006 (1996).
  • K. M. Jones, P.S. Julienne, P.D. Lett, W.D. Phillips, E. Tiesinga, and C.J. Williams, "Measurement of the atomic Na(3P) lifetime and of retardation in the interaction between atoms bound in a molecule," Europhys. Lett. 35 (2), 85 (1996).
  • E. Tiesinga, C.J. Williams, P.S. Julienne, K.M. Jones, P.D. Lett and W.D. Phillips, " A Spectroscopic Determination of Scattering Lengths for Sodium Atom Collisions," J. Res. Natl. Inst. Stand. Technol. 101 , 505 (1996)
  • K.M. Jones,S. Maleki, L.P. Ratliff and P.D. Lett, "Two-Colour Photoassociation Spectroscopy of Ultracold Sodium," J. Phys. B 30, 289 (1997)
  • Y.M. Liu,J.A. Li, D.Y. Chen, L. Li, K.M. Jones,B. Ji, R.J. Le Roy, "Molecular constants and Rydberg-Klein-Rees potential curve for the Na2 1 3Sigmag- State," J. Chem. Phys. 111 (8), 3494 (1999)
  • K.M. Jones, P.D. Lett, E.Tiesinga, and P.S. Julienne, "Fitting line shapes in photoassociation spectroscopy of ultracold atoms: a useful approximation," Phys. Rev. A 61, 012501 (2000).
  • A.Amelink, K.M. Jones, P.D. Lett, P. van der Straten and H.G.M. Heideman, "Spectroscopy of autoionizing doubly-excited states in ultracold Na2 molecules produced by photoassociation," Phys. Rev. A 61, 042707 (2000).
  • A. Amelink, K.M. Jones, P.D. Lett, P. van der Straten and H.G.M. Heideman, "Single- Color Photoassociative Ionization of Ultracold Sodium: The region from 0 to -5 GHz, Phys. Rev. A 62, 013408 (2000)
  • F.K. Fatemi, K.M. Jones and P.D. Lett, "Observation of Optically Induced Feshbach Resonances in Collisions of Cold Atoms," Phys. Rev. Lett. 85, 4462 (2000)
  • Fredrik Fatemi, Kevin M. Jones, He Wang, Ian Walmsley, and Paul D. Lett, "Dynamics of photoinduced collisions of cold atoms probed with picosecond laser pulses," Phys. Rev. A 64, 033421 (2001)
  • C. McKenzie, J. Hecker Denschlag, H. Haffner, A. Browaeys, Luis E. E. de Araujo, F.K. Fatemi, K.M. Jones, J. E. Simsarian, D. Cho, A. Simoni, E. Tiesinga, P.S. Julienne, K. Helmerson, P.D. Lett, S.L. Rolston, and W.D. Phillips, "Photoassociation of Sodium in a Bose-Einstein Condensate," Phys. Rev. Lett. 88, 120403 (2002)
  • Fredrik K. Fatemi, Kevin M. Jones, Paul D. Lett, and Eite Tiesinga, "Ultracold ground-state molecule production in sodium," Phys. Rev. A 66, 053401 (2002)
  • Luís E. E. de Araujo, Jonathan D. Weinstein, Stephen D. Gensemer, Fredrik K. Fatemi, Kevin M. Jones, Paul D. Lett, and Eite Tiesinga, "Two-color photoassociation spectroscopy of the lowest triplet potential of Na2," J. Chem. Phys. 119, 2062 (2003)
  • Eite Tiesinga, Kevin M. Jones, Paul D. Lett, Udo Volz, Carl J. Williams, and Paul S. Julienne , "Measurement and modeling of hyperfine- and rotation-induced state mixing in large weakly bound sodium dimers," Phys. Rev. A 71, 052703 (2005)
  • K. Xu, Y. Liu, J.R. Abo-Shaeer, T. Mukaiyama, J.K. Chin, D.E. Miller, W. Ketterle, Kevin M. Jones, and Eite Tiesinga, "Sodium Bose-Einstein condensates in an optical lattice," Phys. Rev. A 72, 043604 (2005).
  • R. Dumke, J. D. Weinstein, M. Johanning, K. M. Jones, and P. D. Lett, „Sub-Natural-Linewidth Quantum Interference Features Observed in Photoassociation of a Thermal Gas,‰ Phys. Rev. A 72, 041801 (2005) (Rapid Communications).
  • Kevin M. Jones, Eite Tiesinga, Paul D. Lett and Paul S. Julienne, "Ultracold photoassociation spectroscopy: Long-range molecules and atomic scattering," Rev. Mod. Phys. 78, 483 (2006)
  • R. Dumke, M. Johanning, E. Gomez, J.D. Weinstein, K. M. Jones and P. D. Lett, "All-optical generation and photoassociative probing of sodium Bose-Einstein condensates," New J. Phys. 8, 64 (2006)
  • A. M. Marino, V. Boyer, R. C. Pooser, P. D. Lett,1, K. Lemons (Williams '08) and K. M. Jones, "Delocalized Correlations in Twin Light Beams with Orbital Angular Momentum," Phys. Rev. Lett. 101, 093602 (2008)
  • R. C. Pooser, A. M. Marino, V. Boyer, K. M. Jones, and P. D. Lett, "Low-Noise Amplification of a Continuous-Variable Quantum State," Phys. Rev. Lett. 103, 010501 (2009)
  • R. C. Pooser, A. M. Marino, V. Boyer, K. M. Jones, and P. D. Lett, "Quantum correlated light beams from non- degenerate four-wave mixing in an atomic vapor: the D1 and D2 lines of 85Rb and 87Rb," Optics Express 17 16722 (2009)

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