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Nobel 1989

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Experiments with Separated Oscillatory Fields and Hydrogen Masers

Experiments with an Isolated Subatomic Particle at Rest

Electromagnetic Traps for Charged and Neutral Particles

"for the invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks"

"for the development of the ion trap technique"

Norman F. Ramsey	Hans G. Dehmelt	Wolfgang Paul

1/2 of the prize	1/4 of the prize	1/4 of the prize
USA	USA	Federal Republic of Germany
Harvard University Cambridge, MA, USA	University of Washington Seattle, WA, USA	University of Bonn Bonn, Federal Republic of Germany
b. 1915	b. 1922 (in Görlitz, Germany)	b. 1913 d. 1993

Autobiography: Norman F. Ramsey

I was born August 27, 1915 in Washington, D.C. My mother, daughter of German immigrants, had been a mathematics instructor at the University of Kansas. My father, descended from Scottish refugees and a West Point graduate, was an officer in the Army Ordnance Corps. His frequently changing assignments took us from Washington, DC to Topeka, Kansas, to Paris, France, to Picatinny Arsenal near Dover, New Jersey, and to Fort Leavenworth, Kansas. With two of the moves I skipped a grade and, encouraged by my supportive parents and teachers, I graduated from high school with a high academic record at the age of 15.

My early interest in science was stimulated by reading an article on the quantum theory of the atom. But at that time I did not realize that physics could be a profession. My parents presumed that I would try to follow my father's footsteps to West Point, but I was too young to be admitted there. I was offered a scholarship to Kansas University but my parents again moved - this time to New York City. Thus I entered Columbia College in 1931, during the great depression. Though I started in engineering, I soon learned that I wanted a deeper understanding of nature than was then expected of engineers so I shifted to mathematics. By winning yearly competitive mathematics contests, I was honored in my senior year by being given the mathematics teaching assistantship normally reserved for graduate students. At the time I graduated from Columbia in 1935, I discovered that physics was a possible profession and was the field that most excited my curiosity and interest.

Columbia gave me a Kellett Fellowship to Cambridge University, England, where I enrolled as a physics undergraduate. The Cavendish Laboratory in Cambridge was then an exciting world center for physics with a stellar array of physicists: J.J. Thomson, Rutherford, Chadwick, Cockcroft, Eddington, Appleton, Born, Fowler, Bullard, Goldhaber and Dirac. An essay I wrote at Cambridge for my tutor, Maurice Goldhaber, first stimulated my interest in molecular beams and in the possibility of later doing my Ph. D. research with I.I. Rabi at Columbia.

After receiving from Cambridge my second bachelors degree, I therefore returned to Columbia to do research with Rabi. At the time I arrived Rabi was rather discouraged about the future of molecular beam research, but this discouragement soon vanished when he invented the molecular beam magnetic resonance method which became a potent source for new fundamental discoveries in physics. This invention gave me the unique opportunity to be the first graduate student to work with Rabi and his associates, Zacharias, Kellogg, Millman and Kusch, in the new field of magnetic resonance and to share in the discovery of the deuteron quadrupole moment.

Following the completion of my Columbia thesis, I went to Washington, D.C. as a Carnegie Institution Fellow, where I studied neutron-proton and proton-helium scattering.

In the summer of 1940 I married Elinor Jameson of Brooklyn, New York, and we went to the University of Illinois with the expectation of spending the rest of our lives there, but our stay was short lived. World War II was rampant in Europe and within a few weeks we left for the MIT Radiation Laboratory. During the next two years I headed the group developing radar at 3 cm wavelength and then went to Washington as a radar consultant to the Secretary of War. In 1943 we went to Los Alamos, New Mexico, to work on the Manhattan Project.

As soon as the war ended I eagerly returned to Columbia University as a professor and research scientist. Rabi and I immediately set out to revive the molecular beam laboratory which had been abandoned during the war. My first graduate student, William Nierenberg, and I measured a number of nuclear magnetic dipole and electric quadrupole moments and Rabi and I started two other students, Nafe and Nelson, on a fundamental experiment to measure accurately the atomic hydrogen hyperfine separation. During this period Rabi and I also initiated the actions that led to the establishment of the Brookhaven National Laboratory on Long Island, New York, where in 1946 I became the first head of the Physics Department.

In 1947 I moved to Harvard University where I taught for 40 years except for visiting professorships at Middlebury College, Oxford University, Mt. Holyoke College and the University of Virginia. At Harvard I established a molecular beam laboratory with the intent of doing accurate molecular beam magnetic resonance experiments, but I had difficulty in obtaining magnetic fields of the required uniformity. Inspired by this failure, I invented the separated oscillatory field method which permitted us to achieve the desired accuracy with the available magnets. My graduate students and I then used this method to measure in many different molecules a number of molecular and nuclear properties including nuclear spins, nuclear magnetic dipole and electric quadrupole moments, rotational magnetic moments of molecules, spin-rotational interactions, spin-spin interactions, electron distributions in molecules, etc. Although we studied a wide variety of molecules we concentrated on the diatomic molecules of the hydrogen isotopes since these molecules were most suitable for comparing theory and experiment. During this period I also consulted with various groups that were applying the separated oscillatory field method to atomic clocks and I analyzed the precautions which must be taken to avoid errors. Although our original molecular beam research was only with the magnetic resonance method, we later built a separated oscillatory fields electric resonance apparatus and used it to study polar molecules.

In an effort to attain even greater accuracy and to do so with atomic hydrogen, the simplest fundamental atom, Daniel Kleppner, a former student, and I invented the atomic hydrogen maser. We then used it for accurate measurements of the hyperfine separations of atomic hydrogen, deuterium and tritium and for determining the extent to which the hyperfine structure was modified by the application of external electric and magnetic fields. We also participated with Robert Vessot and others in converting a hydrogen maser to a clock of unprecedented stability.

While these experiments were being carried out with some of my graduate students, I worked with other students and associates to apply similar precision methods to beams of polarized neutrons. At the Institut Laue-Langevin in Grenoble, France, we measured accurately the magnetic moment of the neutron, set a low limit to the electric dipole moment of the neutron as a test of time reversal symmetry and discovered and measured the parity non-conserving rotations of the spins of neutrons passing through various materials.

Concurrently with my molecular and neutron beam research, I was also teaching and involved with other scientific activities. I was director of the Harvard Cyclotron during its construction and early operation and participated in proton-proton scattering experiments with that cyclotron. I was later chairman of the joint Harvard-MIT committee managing the construction of the 6 GeV Cambridge Electron Accelerator and used that device for various particle physics experiments including electron-proton scattering. For a year and a half I was on leave from Harvard as the first Assistant Secretary General for Science (Science Advisor) in NATO where I initiated the NATO programs for Advanced Study Institutes, Fellowships and Research Grants. For sixteen exciting years I was on leave half time from Harvard as President of Universities Research Association which exercised its management responsibilities for the construction and operation of the Fermilab accelerator through two outstanding laboratory directors, Robert R. Wilson and Leon Lederman.

Although I am primarily an experimental physicist, theoretical physics is my hobby and I have published several theoretical papers including early discussions of parity and time reversal symmetry, the first successful theory of the NMR chemical shifts, theories of nuclear interactions in molecules and the theory of thermodynamics and statistical mechanics at negative absolute temperatures.

I officially retired from Harvard in 1986, but I have remained active in physics. For one year I was a research fellow at the Joint Institute for Laboratory Astrophysics at the University of Colorado and I now periodically revisit JILA as an Adjunct Research Fellow. Subsequent to our year in Colorado, I have been visiting professors at The University of Chicago, Williams College and the University of Michigan. I continue writing and theoretical calculations in my Harvard office and with my collaborators we are continuing our neutron experiments at Grenoble.

After Elinor died in 1983, I married Ellie Welch of Brookline, Massachusetts and we now have a combined family of seven children and six grandchildren. We enjoy downhill and cross country skiing, hiking, bicycling and trekking as well as musical and cultural events.

I have greatly enjoyed my years as a teacher and research physicist and continue to do so. The research collaborations and close friendships with my eighty-four graduate students have given me especially great pleasure. I hope they have learned as much from me as I have from them.

Books
Experimental Nuclear Physics, with E. Segre, John Wiley and Sons, Inc. (1953), Nuclear Moments, John Wiley and Sons, Inc. (1953), Molecular Beams, Oxford University Press (1956 and 1985) and Quick Calculus, with D. Kleppner, John Wiley and Sons, Inc. (1965 and 1985).

Honorary D. Sc.
Case-Western Reserve University, Middlebury College, Oxford University, The Rockefeller University, The University of Chicago and The University of Sussex.

Honors
E. O Lawrence Award, 1960; Trustee Carnegie Endowment for International Peace, 1962 - 86; Davisson-Germer Prize, 1974; Trustee of The Rockefeller University, 1977 - ; President of the American Physical Society, 1978 - 79; Chairman Board of Governors of American Institute of Physics, 1980 - 86; President of United Chapters of Phi Beta Kappa, 1984 - 88; IEEE Medal of Honor, 1984; Rabi Prize, 1985; Rumford Premium, 1985; Chairman Board of Physics and Astronomy of National Research Council, 1985 - 1989; Compton Medal, 1986; Oersted Medal, 1988; National Medal of Science, 1988.

Principal Publications
1. Magnetic Moments of Proton and Deuteron. Radiofrequency Spectrum of H₂ in Magnetic fields. With J.M.B. Kellogg, I.I. Rabi and J.R. Zacharias, Phys. Rev. 56, 728 (1939).

2. Electrical Quadrupole Moment of the Deuteron. Radiofrequency Spectra of HD and D₂ Molecules in a Magnetric Field. With J. M. B. Kellogg, I. I. Rabi and J.R. Zacharias, Phys. Rev. 57, 677 (1940).

3. Rotational Magnetic Moments of H₂, D₂ and HD molecules. Phys. Rev. 58, 226 (1940).

4. Molecular Beam Resonance Method with Separated Oscillating Fields. Phys. Rev. 78, 695 (1950).

5. Magnetic Shielding of Nuclei in Molecules. Phys. Rev. 78, 699 (1950).

6. On the Possibility of Electric Dipole Moments for Elementary Particles and Nuclei. With E.M. Purcell, Phys. Rev. 78, 807(L) (1950).

7. Nuclear Audiofrequency Spectroscopy by Resonant Heating of the Nuclear Spin System. With R.V. Pound, Phys. Rev. 81, 278(L) (1951).

8. Proton-Proton Scattering at 105 MeV and 75 MeV. With R.W. Brige and U.E. Kruse, Phys. Rev. 83, 274 (1951).

9. Theory of Molecular Hydrogen and Deuterium in Magnetic Fields. Phys. Rev. 85, 60 (1952).

10. Chemical Effects in Nuclear Magnetic Resonance and in Diamagnetic Susceptibility. Phys. Rev. 86, 243 (1952).

11. Nuclear Radiofrequency Spectra of H₂ and D₂ in High and Low Magnetic Fields. With H.G. Kolsky, T.E. Phipps, and H.B. Silsbee, Phys. Rev. 87, 395 (1952).

12. Nuclear Radiofrequency Spectra of D₂ and H₂ in Intermediate and Strong Magnetic Fields. With N.J. Harrick, R.G. Barns and P.J. Bray, Phys. Rev. 90, 260 (1953).

13. Electron Coupled Interations between Nuclear Spins in Molecules. Phys. Rev. 91, 303 (1953).

14. Use of Rotating Coordinates in Magnetic Resonance Problems. With I. I. Rabi andJ. Schwinger, Rev. Mod. Phys. 26, 167 (1954).

15. Resonance Transitions Induced by Perturbations at Two or More Different Frequencies. Phys. Rev. 100, 1191 (1955).

16. Thermodynamics and Statistical Mechanics at Negative Absolute Temperatures, Phys. Rev. 103, 20 (1956).

17. Molecular Beams, Published by Oxford University Press, England (1956).

18. Resonance Experiments in Successive Oscillatory Fields. Rev. Sci. Instr. 28, 57(L) (1957).

19. Experimental Limit to the Electric Dipole Moment of the Neutron. With J.H. Smith and E.M. Purcell, Phys. Rev. 108, 120 (1957).

20. Time Reversal, Charge Conjugation, Magnetic Pole Conjugation, and Parity. Phys. Rev. 109, 225 (1958).

21. Molecular Beam Resonances in Oscillatory Fields of Nonuniform Amplitudes and Phases. Phys. Rev. 109, 822 (1958).

22. Radiofrequency Spectra of Hydrogen Deuteride in Strong Magnetic Fields. With W.E. Quinn, J.M. Baker, J.T. LaTourrette, Phys. Rev. 112, 1929 (1958).

23. On the Significance of Potentials in Quantum Theory. With W.H. Furry, Phys. Rev. 118, 623 (1960).

24. Atomic Hydrogen Maser. With H.M. Goldenberg and D. Kleppner, Phys. Rev. Letters 8, 361 (1960).

25. Theory of the Hydrogen Maser. With D. Kleppner and H.M. Goldenberg, Phys. Rev. 126, 603 (1962).

26. Hyperfine Structure of Ground State of Atomic Hydrogen. With S.B. Crampton, and D. Kleppner, Phys. Rev. Letters 11, 338 (1963).

27. Hydrogen Maser Principles and Techniques. With D. Kleppner, H.C. Berg, S.B. Crampton, R.F.C. Vessot, H.E. Peters and J. Vanier, Phys. Rev. 138, A972 (1965).

28. Measurement of Proton Electromagnetic Form Factors at High Momentum Transfer. With K.W. Chen, J.R. Dunning, Jr., A.A. Cone, J.K. Walker and Richard Wilson, Phys. Rev. 141, 1267 (1966).

29. Absolute Value of the Proton g Factor. With T. Myint, D. Kleppner and H.G. Robinson, Phys. Rev. Lett. 17, 405 (1966).

30. Magnetic Resonance Molecular Beam Spectra of Methane. With C.H. Anderson, Phys. Rev. 149, 14 (1966).

31. Hyperfine Separation of Tritium. With B.S. Mathur, S.B. Crampton, and D. Kleppner, Phys. Rev. 158, 14 (1967).

32. Measurement of the Hydrogen-Deuterium Atomic Magnetic Moment Ratio and of the Deuterium Hyperfine Frequency. With D.J. Larson and P.A. Valberg, Phys. Rev. Letters 23, 1369 (1969).

33. Multiple Region Hydrogen Maser with Reduced Wall Shift. With E.E. Uzgiris, Phys. Rev. Al, 429 (1970).

34. Molecular Beam Magnetic Resonance Studies of HD and D₂. With R.F. Code, Phys. Rev. A4, 1945 (1971).

35. Atomic Deuterium Maser With D.J. Wineland, Phys. Rev. A5, 821 (1972).

36. The Molecular Zeeman and Hyperfine Spectra of LiH and LiD by Molecular Beam High Resolution Electric Resonance. With Richard R. Freeman, Abram R. Jacobson, and David W. Johnson, J. of Chem. Physics 63, 2597 (1975).

37. The Tensor Force Between Two Protons at Long Range, Physica 96A, 285 (1979)

38. Measurement of the Neutron Magnetic Moment. With G.L. Green, W. Mampe, J.M. Pendelbury, K. Smith, W.B. Dress, P. D. Miller and P. Perrin, Phys. Rev. D20, 2139 (1979).

39. First Measurement of Parity-Nonconserving Neutron Spin Rotation: The Tin Isotopes. With M. Forte, B.R. Heckel K. Green, and G.L. Greene, Phys. Rev. Lett. 45, 2088 (1980).

40. Search for P and T Violations in the Hyperfine Structure of Thallium Fluoride. With D.A. Wilkening and D.J. Larson, Phys. Rev. A29, 425 (1984).

41. Search for a Neutron Electric Dipole Moment. With J.M. Pendlebury, et al., Phys. Letters 136B, 327 (1984).

42. Neutron Magnetic Resonance Experiments. Physica 137B, 223 (1986).

43. Quantum Mechanics and Precision Measurements, IEEE Transactions on Instrumentation and Measurement IM36, 155 (1987).

44. Precise Measurements of Time. American Scientist 76, 42 (1988).

45. The Electric Dipole Moment of the Neutron. Physical Scripta T22, 40 (1988).

From Les Prix Nobel. The Nobel Prizes 1989, Editor Tore Frängsmyr, [Nobel Foundation], Stockholm, 1990

Autobiography: Hans G. Dehmelt

My father, Georg, had studied law at the Universität Berlin for some years, and in the first World War had been an artillery officer. He was of a philosophical bend of mind and a man of independent opinions. In the depth of the depression he just managed to make a living in real estate. When the family fortunes had shrunk to ownership of a heavily mortgaged apartment building located in an overwhelmingly Communist part of Berlin, it seemed reasonable to move into one of the apartments ourselves as nobody paid any rent. Cannons were deployed on the streets on occasion and the class war had entered the class rooms. After a few bloody noses administered by a burly repeater, I shifted my interests from roaming the streets more towards playing with rudimentary radio receivers and noisy and smelly experiments in my mother's kitchen. In the spring of 1933 my mother, a very energetic lady, saw to it that, at the age of ten, I entered the Gymnasium zum Grauen Kloster, the oldest Latin school in Berlin, which counted Bismarck amongst its Alumni. This involved a stiff entrance examination and I was admitted on a scholarship. My father at that time expressed the opinion that I probably would be happier as a plumber. However, he apparently didn't quite believe this himself. Thus, in years before, he had bought me an erector set and books on the lives of famous inventors and Greek mythology, and when I was ill he had given me the encyclopedia to read. I supplemented the school curriculum with do-it-yourself radio projects until I had hardly any time left for my class work. Only tutoring from my father rescued me from disaster. Reading popular radio books deepened my interest in physics. While physics was taught at the Kloster only in the later grades, in the public library I read books with titles such as "Umsturz im Weltbild der Physik" and learned about the Balmer series and Bohr's energy levels of the hydrogen atom. My teachers at the Kloster were excellent, I remember in particular Dr. Richter, who taught Latin and Greek, and Dr. Splettstoesser, who taught biology and physics. Richter liked to expand on the classical works, which we were reading in class. I spent most of the ample breaks in related intense discussions with a group of classmates, Heppke, Hubner, Landau and Leiser while others engaged in boxing matches. Splettstoesser was a working scientist who spent Summers as a visitor with a marine biology institute on the Adriatic. I jumped a term and graduated in the spring of 1940.

Having received a notice from the draft board, I found it wise to volunteer for the anti-aircraft artillery and a motorized unit. I was not able to serve as a radio man but was assigned to a gun crew and never rose above the rank of senior private. Sent to relieve the German armies at Stalingrad, my battery was extremely lucky to escape the encirclement. A few months later I was even more lucky to be ordered back to Germany to study physics under an army program at the Universität Breslau in 1943. After one year of study, I was sent to the Western Front and captured in the Battle of the Bulge. I spent a year in an American prisoner of war camp in France and was released early in 1946. Supporting myself with the repair and barter of prewar radios, I took up my study of physics again at the Universität Göttingen. Here I attended lectures by Pohl, Richard Becker, Hans Kopfermann and Werner Heisenberg; Max v. Laue and Max Planck attended the physics colloquia. At the funeral of Planck I was chosen to be one of the pall bearers. At the university, I greatly enjoyed repeating the Frank-Hertz experiment, the Millikan oil drop, Zeemann effect, Hull's magnetron, Langmuir's plasma tube and other classic modern physics experiments in an excellent laboratory class run by Wolfgang Paul. In one of his Electricity & Magnetism classes Becker drew a dot on the blackboard and declared "Here is an electron..." Having heard in another class that the wave function of an electron at rest spreads out over all of space, and having read about ion trapping in radio tubes in my teens set me to wonder how one might realize Becker's localization feat in the laboratory. However, that had to wait a while. In 1948, in Kopfermann's Institute, which was heavily oriented towards hyperfine structure studies, I completed an experimental Diplom-Arbeit (master's thesis) on a Thomson mass spectrograph under Peter Brix. The results were published in "Die photographischen Wirkungen mittelschneller Protonen II," the first paper of which I was a (co)author. Soon thereafter, I began work on my doctoral thesis under Hubert Kruger in the same Institute. Well prepared by a series of excellent Institute seminars on the NMR work of Bloch and of Purcell, we were able to successfully compete with workers at Harvard University. In 1949 we discovered Nuclear Quadrupole Resonance and reported it in our paper "Kernquadrupolfrequenzen in festem Dichloraethylen." My doctoral thesis had the title "Kernquadrupolfrequenzen in kristallinen Jodverbindungen." This work led to an invitation to join Walter Gordy's well known microwave laboratory at Duke University as postdoctoral associate.

At Duke I had the pleasure of making the acquaintance of James Frank, Fritz London, Lothar Nordheim and Hertha Sponer. I advised Hugh Robinson, a graduate student of Gordy's in an NQR experiment, did my own research and also contributed some NMR expertise to an experiment by Bill Fairbank and Gordy on spin statistics in ³He/⁴He mixtures, gaining some very useful low temperature experience in this brief collaboration. Through Gordy's and Nordheim's good offices I was able to receive a visiting assistant professor appointment at the University of Washington with a charge to advise Edwin Uehling's students during his sabbatical and to do independent research. I had built my first electron impact tube during a brief interlude in 1955 in George Volkoffs laboratory at the University of British Columbia. Prior to that I had attempted a paramagnetic resonance experiment on free atoms in Gottingen and succeeded in doing so at Duke. During seminars at Göttingen on the magnetic resonance techniques of Rabi and of Kastler, it had occurred to me that because of the analogy between an atom and a radio dipole antenna, (a), alignment of the atom should show up in its optical absorption cross section, and (b), electron impact should produce aligned excited atoms. I put these two ideas to good use in 1956 in Seattle in an experiment entitled "Paramagnetic Resonance Reorientation of Atoms and Ions Aligned by Electron Impact." In this paper I first pointed out the usefulness of ion trapping for high resolution spectroscopy and mentioned the 1923 Kingdon trap as a suitable device. This work also brought me into close contact with spin exchange between electron and target atom, which gave me the idea for my 1958 experiment "Spin Resonance of Free Electrons Polarized by Exchange Collisions." However, first I had to learn how to produce polarized atoms, which could then transfer their orientation to trapped electrons. Falling back on buffer gas techniques developed in my 1955 Duke paper "Atomic Phosphorus Paramagnetic Resonance Experiment," I quickly demonstrated in my 1956 Seattle paper "Slow Spin Relaxation of Optically Polarized Sodium Atoms" how to efficiently produce and monitor a polarized atom cloud. Trapping the electrons in a neutralizing ion cloud slowly diffusing in the buffer gas, I was able to carry out the spin resonance experiment. My optical transmission monitoring scheme proved also very useful in the development of rubidium vapor magnetometers and frequency standards by Earl Bell and Arnold Bloom at Varian Associates, in which I acted as a consultant. The rubidium frequency standard is still the least expensive, smallest and most widely used commercial atomic frequency standard. The thesis "Experimental Upper Limit for the Permanent Electric Dipole Moment of Rb⁸⁵ by Optical Pumping Techniques" of my first graduate student, Earl Ensberg, also made use of these novel optical pumping schemes and was finished in 1962. These early results were improved orders of magnitude by my doctoral student Philip Ekstrom in his 1971 thesis "Search for Differential Linear Stark Shift in Cs¹³³ and Rb⁸⁵ Using Atomic Light Modulation Oscillators."

I was not satisfied with the plasma trapping scheme used for the electrons and asked my student, Keith Jefferts, to study ion trapping in an electron beam traversing a field free vacuum space between two grids. Also, I began to focus on the magnetron/Penning discharge geometry, which, in the Penning ion gauge, had caught my interest already at Göttingen and at Duke. In their 1955 cyclotron resonance work on photoelectrons in vacuum Franken and Liebes had reported undesirable frequency shifts caused by accidental electron trapping. Their analysis made me realize that in a pure electric quadrupole field the shift would not depend on the location of the electron in the trap. This is an important advantage over many other traps that I decided to exploit. A magnetron trap of this type had been briefly discussed in J.R. Pierce's 1949 book, and I developed a simple description of the axial, magnetron, and cyclotron motions of an electron in it. With the help of the expert glassblower of the Department, Jake Jonson, I built my first high vacuum magnetron trap in 1959 and was soon able to trap electrons for about 10 sec and to detect axial, magnetron and cyclotron resonances. About the same time, my Göttinger colleague, Otto Osberghaus, sent me a research report on the Paul rf ion cage. This trap had very desirable properties for atomic ions and it did not require a magnetic field. Therefore, I asked my student, Fouad Major, to experiment with a simplified cylindrical version of such a trap in the hope that it might be useful in hfs resonance experiments on hydrogenic helium ions. The early results were very encouraging and Jefferts also switched to the Paul trap. In 1962, Jefferts and Major both finished their Doctoral Theses entitled respectively "Alignment of Trapped H₂⁺ Molecular Ions by Selective Photodissociation" and "The Orientation of Electrodynamically Contained He⁴ Ions." As a continuation of the latter, a new postdoc, Norval Fortson, Major and I published the 1966 paper "Ultrahigh Resolution DF=0 ± 1³He⁺ HFS Spectra by an Ion Storage-Exchange Collision Technique." My own attempts to detect the polarization of the electrons acquired from a polarized beam of alkali atoms in my Penning (magnetron) trap, described in a 1961 research report to the NSF "Spin Resonance of Free Electrons," were not so quickly successful. However in this work I was much impressed by seeing the beam of sodium atoms traversing my glass apparatus in the reflected light from a sodium vapor street lamp adapted as illuminating light source. Only a later concerted effort by Gräff and Werth at Bonn, reinforced by Major and Fortson, as visitors, made a similar spin resonance experiment work in 1968.

In the 1966 paper with Fortson and Major, I also proposed to develop an infrared laser based on ions in an rf trap. To this end my student, David Church, completed a thesis in 1969 entitled "Storage and Radiative Cooling of Light Ion Gases in RF Quadrupole Traps." In this work we demonstrated a race-track-shaped trap and cooled the ions by coupling to a resonant LC circuit. In parallel work my student, Stephan Menasian, in 1968, with some help from G.R. Huggett, succeded in cooling Hg⁺ ions in a race-track-trap with a helium buffer gas and in detecting them by optical absorption. Jefferts' research on hfs spectra of H₂⁺ was continued in Seattle by my postdoc Charles Richardson and later by Menasian in his 1973 doctoral thesis "High Resolution Study of the (1, 1/2, 1/2) - (1, 1/2,3/2) HFS Transition in H₂⁺." The resolution in the ³He⁺ hfs work was greatly enhanced in work with my colleague Fortson and my postdoc Hans Schuessler. Realizing in 1961 that precision measurements of the electron magnetic moment would require a large magnetic field and that Becker's electron localization feat might be approximated in a Penning trap, I began to consider other avenues for magnetic resonance experiments. Some success in the electron work, achieved with the help of my new student, Fred Walls, was described in our 1968 paper "'Bolometric' Technique for the RF Spectroscopy of Stored Ions." I reviewed the work on ions and electrons up to 1968 in two articles "Radiofrequency Spectroscopy of Stored Ions."

The able assistance of two postdocs, David Wineland and my former student Phil Ekstrom, made the isolation of a single electron become a reality in 1973 with our paper "Monoelectron Oscillator." Measuring its magnetic moment was another story. At Göttingen in the late forties I had attended a seminar given by Helmut Friedburg, a doctoral Student of Wolfgang Paul, on focussing spins with a magnetic hexapole. This may be viewed as a refinement of the Stern-Gerlach effect. In subsequent discussions with fellow students a rumor of a Stern-Gerlach experiment for electrons was brought up, and also Bohr's and Pauli's thesis that such experiments were impossible in principle. Though it greatly piqued my interest, I could not understand this thesis. Stimulated by a 1927 paper of Brillouin on the subject, I followed another of the guiding principles formulated by Bohr: "In my Institute we take nothing absolutely serious, including this statement." In 1973 I proposed, together with Ekstrom, to monitor spin and cyclotron quantum numbers of the lone electron by means of the "continuous Stern-Gerlach effect" in an abstract "Proposed g-2/dv_z Experiment on Stored Single Electron or Positron." My new postdoc Robert Van Dyck, Philip Ekstrom and myself reported the first such experiment in our 1976 paper "Axial, Magnetron, and Spin-Cyclotron Beat Frequencies Measured on Single Electron Almost at Rest in Free Space (Geonium)." This work also already made use of the important technique of side band cooling of the electron. The demonstration of sideband cooling had eluded us in earlier attempts undertaken together with Walls and later with Wineland. Encouraged by the success of the monoelectron oscillator I had also published in 1973 an abstract "Proposed 10¹⁴ Dv < v Laser Fluorescence Spectroscopy on Tl⁺ Mono-Ion Oscillator." Unfortunately, this proposal infuriated one of the agencies funding our research to the degree that they terminated their support almost immediately. I was rescued by a prize from the Humboldt Foundation and an invitation by Gisbert zu Putlitz to initiate the proposed laser spectroscopy project in his Institute at the Universität Heidelberg. As the fruit of these efforts a paper "Localized visible Ba⁺ mono-ion oscillator" by Neuhauser, Hohenstatt, Toschek and myself appeared in 1980.

In 1981 Van Dyck, my doctoral student Paul Schwinberg and myself extended the electron work to its antiparticle in our paper "Preliminary Comparison of the Positron and Electron Spin Anomalies" and I reviewed it in an article "Invariant Frequency Ratios in Electron and Positron Geonium Spectra Yield Refined Data on Electron Structure." In 1986 we published a detailed paper "Electron Magnetic Moment from Geonium Spectra: Early Experiments and Background Concepts" and in 1987 our collaboration reported a 4 parts in 10¹² resolution in the g factor for electron and positron in "New High-Precision Comparison of Electron and Positron g Factors." A very promising scheme to detect cyclotron excitation through the small relativistic mass increase accompanying it was published in a 1985 paper "Observation of Relativistic Bistable Hysteresis in the Cyclotron Motion of a Single Electron" together with my postdoc, Gerald Gabrielse, and William Kells, a visitor from Fermi Lab.

Two years after the Heidelberg pioneering work an individual magnesium ion was isolated in Seattle with my postdoc Warren Nagourney and my student Gary Janik. The latter's thesis bore the title "Laser Cooled Single Ion Spectroscopy of Magnesium and Barium." "Shelved optical electron amplifier: Observation of quantum jumps," was published in 1986 with my colleague Nagourney, and Jon Sandberg, an exceptional undergraduate assistant. The paper introduced a new technique which has made optical spectroscopy on an individual ion possible with record resolution and reproducibility. To date the best resolution has been realized at NIST by a group headed by my former collaborator Wineland. Peter Toschek who had made important contributions to the visible ion work in Heidelberg has built up a thriving laboratory for monoion-spectroscopy at the Universität Hamburg. With Herbert Walther a collaboration almost came off in 1974. Walther, with his large staff and excellent facilities in Munich, has since developed his own expertise in the field and made outstanding contributions to it. Gabrielse, now a full professor at Harvard, has assembled a large group and is trapping and cooling antiprotons at CERN.

In the 1988 paper "A Single Atomic Particle Forever Floating at Rest in Free Space: New Value for Electron Radius" I have surveyed the field and suggested new avenues for its extension. More precise measurements of the g factor of the electron may well be the most promising approach to study its structure. No less important, a trapped individual atomic ion may reveal itself as a timekeeping element of unsurpassed reproducibility. The research effort in Seattle continues on troth projects. The National Science Foundation has supported my research since 1958 without interruption. Initially the Army Office of Ordnance Research and the Office of Naval Research did also provide support for many years.

I am married to Diana Dundore, a practising physician. I have a grown son, Gerd, from an earlier marriage to Irmgard Lassow who is deceased.

I do regular hatha yoga exercises, enjoy waltzing, hiking in the foothills, reading, listening to classical music, and watching ballet performances.

Selected Publications

"Die photographischen Wirkungen mittelschneller Protonen II", P. Brix and H. Dehmelt, Z. Physik 126, 728 (1949)

"Kernquadrupolfrequenzen in festem Dichloraethylen", H. Dehmelt and H. Krueger, Naturwissenschaften 37, 111 (1950)

"Nuclear Quadrupole Resonance", H. Dehmelt, Am. J. Phys. 22, 110 (1954)

Atomic Phosphorus Paramagnetic Resonance Experiment", H. Dehmelt, Phys. Rev. 99,527 (1955)

"Paramagnetic Resonance Reorientation of Atoms and Ions Aligned by Electron Impact" H. Dehmelt, Phys. Rev. 103, 1125 (1956)

"Slow Spin Relaxation of Optically Polarized Sodium Atoms", H. Dehmelt, Phys. Rev. 105, 1487 (1957)

"Modulation of a Light Beam by Precessing Absorbing Atoms" H. Dehmelt, Phys. Rev. 105, 1924 (1957)

"Spin Resonance of Free Electrons Polarized by Exchange Collisions", H. Dehmelt, Phys. Rev. 109, 381 (1958)

"Spin Resonance of Free Electrons", H. Dehmelt, 1958-61 Progress Report for NSF Grant NSF-G 5955

"Alignment of the H₂⁺ Molecular Ion by Selective Photodissociation", H. Dehmelt and K. Jefferts, Phys. Rev. 125, 1318 (1962)

"Orientation of He Ions by Exchange Collisions with Cesium Atoms", H. Dehmelt and F. Major, Phys. Rev. Lett. 8, 213 (1962)

"Ultrahigh Resolution DF=0, ±1 ³He⁺ HFS Spectra by an Ion Storage - Exchange Collision Technique", N. Fortson, F. Major and H. Dehmelt, Phys. Rev. Lett. 16, 221 (1966)

"Radiofrequency Spectroscopy of Stored Ions", H. Dehmelt, Adv. At. Mol. Phys. 3, 53 (1967) and 5, 109 (1969)

"Alignment of the H₂⁺ Molecular Ion by Selective Photodissociation II: Experiments on the RF Spectrum," Ch. Richardson, K. Jefferts and H. Dehmelt, Phys. Rev. 165, 80 (1968)

"'Bolometric' Technique for the RF Spectroscopy of Stored Ions", H. Dehmelt and F. Walls, Phys. Rev. Lett. 21, 127 (1968)

"Radiative Cooling of an Electrodynamically Confined Proton Gas", D. Church and H. Dehmelt, J. Appl. Phys. 40, 3421 (1969)

"Proposed g-2/dv_z Experiment on Stored Single Electron or Positron", H. Dehmelt and P. Ekstrom, Bull. Am. Phys. Soc. 18, 727 (1973)

"Monoelectron Oscillator", D. Wineland, P. Ekstrom and H. Dehmelt, Phys. Rev. Lett. 31, 1279 (1973)

"Proposed 10¹⁴ Dv < v Laser Fluorescence Spectroscopy on Tl+ Mono-Ion Oscillator", H. Dehmelt, Bull. Am. Phys. Soc. 18, 1521 (1973)

"Principles of the Stored Ion Calorimeter" D. Wineland and H. Dehmelt, J. Appl. Phys. 46, 919 (1975)

"Proposed 10¹⁴ Dv < v Laser Fluorescence Spectroscopy on Tl+ Mono-Ion Oscillator II (spontaneous quantum jumps)", H. Dehmelt, Bull. Am. Phys. Soc. 20, 60 (1975)

"Proposed 10¹⁴ Dv < v Laser Fluorescence Spectroscopy on Tl+ Mono-Ion Oscillator III (side band cooling)", D. Wineland and H. Dehmelt, Bull. Am. Phys. Soc. 20, 637 (1975)

"Axial, Magnetron, Cyclotron and Spin-Cyclotron Beat Frequencies Measured on Single Electron Almost at Rest in Free Space (Geonium)", Van Dyck, Jr., R.S., Ekstrom, P., and Dehmelt, H., Nature 262, 776 (1976)

"Entropy Reduction by Motional Side Band Excitation", Dehmelt, H., Nature 262, 777 (1976)

"A Progress Report on the g-2 Resonance Experiments", H. Dehmelt, in Atomic Musses and Fundamental Constants, Volume 5 (eds. J. H. Sanders, and A. H. Wapstra), p. 499. Plenum New York, 1976

"Precise Measurement of Axial, Magnetron, Cyclotron and Spin-Cyclotron Beat Frequencies on an Isolated 1-meV Electron", Van Dyck, Jr., R.S., Ekstrom, P., and Dehmelt, H., Phys. Rev. Lett. 38, 310 (1977)

"Electron Magnetic Moment from Geonium Spectra", Van Dyck, Jr., R.S., Schwinberg, P.B. & Dehmelt, H.G., in New Frontiers in High Energy Physics (Eds. B. Kursunoglu, A. Perlmutter, and L. Scott), Plenum New York, 1978

"Optical Sideband Cooling of Visible Atom Cloud Confined in Parabolic Well", Neuhauser, W., Hohenstatt, M., Toschek, P.E., and Dehmelt, H.G., Phys. Rev. Lett. 41, 233 (1978)

"Single Elementary Particle at Rest in Free Space I-IV", Dehmelt, H., Van Dyck, Jr., R.S., Schwinberg, P.B., Gabrielse, G., Bull. Am. Phys. Soc. 24, 757 (1979)

"Localized visible Ba⁺ mono-ion oscillator", Neuhauser, W., Hohenstatt, M., Toschek, P. E., and Dehmelt, H. G., Phys. Rev. A22, 1137 (1980)

"Preliminary Comparison of the Positron and Electron Spin Anomalies", P.B.Schwinberg, R.S. Van Dyck, Jr., and H.G. Dehmelt, Phys. Rev. Lett. 47, 1679 (1981)

"Invariant Frequency Ratios in Electron and Positron Geonium Spectra Yield Refined Data on Electron Structure", Hans Dehmelt, in Atomic Physics 7, D. Kleppner & F. Pipkin Eds., Plenum, New York, 1981

"Mono-Ion Oscillator as Potential Ultimate Laser Frequency Standard", Hans Dehmelt, IEEE Transactions on Instrumentation & Measurement, IM-31, 83 (1982)

"Stored Ion Spectroscopy", Hans Dehmelt, in Advances in Laser spectroscopy, F. T. Arecchi, F. Strumia & H. Walther, Eds., Plenum, New York, 1983

"Geonium Spectra and the Finer Structure of the Electron", R. Van Dyck, P. Schwinberg, G. Gabrielse & Hans Dehmelt, Bulletin of Magnetic Resonance 4, 107 (1983)

"g-Factor of Electron Centered in Symmetric Cavity", Hans Dehmelt, Proc. Natl. Acad. Sci. USA 81, 8037 (1984); Erratum ibidem 82, 6366 (1985)

"Observation of Relativistic Bistable Hysteresis in the Cyclotron Motion of a Single Electron", G. Gabrielse, H. Dehmelt & W. Kells, Phys. Rev. Letters 54, 537 (1985).

"Doppler-Free Optical Spectroscopy on the Ba⁺ Mono-Ion Oscillator", G. Janik, W. Nagourney, H. Dehmelt, J. Opt. Soc. Am. B 2, 1251-1257 (1985)

"Single Atomic Particle at Rest in Free Space: New Value for Electron Radius", Hans Dehmelt, Annales de Physique (Paris) 10, 777 - 795 (1985)

"Observation of Inhibited Spontaneous Emission", G. Gabrielse and H. Dehmelt, Phys. Rev. Lett. 55, 67 (1985)

"Electron Magnetic Moment from Geonium Spectra: Early Experiments and Background Concepts", Van Dyck, Jr., R.S., Schwinberg, P.B. & Dehmelt, H.G., Phys. Rev. D 34, 722 (1986)

"Continuous Stern Gerlach Effect: Principle and idealized apparatus", Hans Dehmelt, Proc. Natl. Acad. Sci. USA 83, 2291 (1986), and 83, 3074 (1986)

"Shelved optical electron amplifier: Observation of quantum lumps", Warren Nagourney, Jon Sandberg, and Hans Dehmelt, Phys. Rev. Letters 56, 2797 (1986)

"New High Precision Comparison of Electron/Positron g-Factors", Van Dyck, Jr, R.S., Schwinberg, P.B. Dehmelt, H.G., Phys. Rev. Letters 59, 26 (1987)

"Single Atomic Particle at Rest in Free Space: Shift-Free Suppression of the Natural Line Width?", Hans Dehmelt, in Laser Spectroscopy VIII, S. Svanberg and W. Persson editors, 1987 (Springer, New York)

"Single Atomic Particle Forever Floating at Rest in Free Space: New Value for Electron Radius", Hans Dehmelt, Physica Scripta T22, 102 (1988)

"New Continuous Stern Gerlach Effect and a Hint of 'The' Elementary Particle", Hans Dehmelt, Z. Phys. D 10, 127-134 (1988)

"Coherent Spectroscopy on a Single Atomic System at Rest in Free Space III", Hans Dehmelt, in Frequency Standards and Metrology, A. de Marchi Ed. (Springer, New York, 1989). p. 15

"Triton,.. electron,.. cosmon ...: An infinite regression? Hans Dehmelt, Proc. Natl. Acad. Sri. USA 86, 8618-8619 (1989)

"Miniature Paul-Straubel ion trap with well-defined deep potential well", Nan Yu, Hans Dehmelt, and Warren Nagourney, Proc. Natl. Acad. Sci. USA 86, 5672 (I 989)

From Les Prix Nobel. The Nobel Prizes 1989, Editor Tore Frängsmyr, [Nobel Foundation], Stockholm, 1990

This autobiography/biography was written at the time of the award and later published in the book series Les Prix Nobel/Nobel Lectures. The information is sometimes updated with an addendum submitted by the Laureate. To cite this document, always state the source as shown above.

Addendum, May 2005

After I had received the Prize in 1989 until my retirement in October 2002 I continued my single electron and single ion work with my associates. In the 1990s, stimulated by the life extension work of Roy Walford I shifted my main effort more and more into this and the Health and Nutrition fields.

Hans Dehmelt

On my University website http://faculty.washington.edu/dehmelt/ are some examples of work in progress. I also published 2 papers, Re-Adaptation Hypothesis: Explaining Health Benefits Of Caloric Restriction & Healthiest Diet Hypothesis: How to Cure Most Diseases? in the peer-reviewed journal Medical Hypotheses. Recently the Karolinska Institute invited me to nominate candidates for the 2005 Prize which I did. Also the journal Theoretical Biology and Medical Modeling asked me to publish my expanded next paper The Healthiest Diet: It Cures Most Diseases with them which I will do. My retirement from teaching was celebrated by a Fest & Festschrift An Isolated Atomic Particle at Rest in Free Space: A Tribute to Hans Dehmelt, Nobel Laureate, E. Norval Fortson and Ernest M. Henley, Editors.

Autobiography: Wolfgang Paul

I was born on August 10, 1913 in Lorenzkirch a small village in Saxony, as the forth child of Theodor and Elisabeth Paul nee Ruppel. All in all we were six children. Both parents were descendants from Lutheran ministers in several generations. I grew up in München where my father has been a professor for pharmaceutic chemistry at the university. He had studied chemistry and medicin having been a research student in Leipzig with Wilhelm Ostwald, the Nobel Laureate 1909. So I became familiar with the life of a scientist in a chemical laboratory quite early. Unfortunately, my father died when I was still a school boy at the age of fifteen years. But my interest in sciences was awaken, even my parents were very much in favour of a humanistic education. After finishing the gymnasium in München with 9 years of latin and 6 years of ancient greek, history and philosophy, I decided to become a physicist. The great theoretical physicist, Arnold Sommerfeld, an University colleague of my late father, advised me to begin with an apprenticeship in precision mechanics. Afterwards, in the fall 1932, I commenced my studies at the Technische Hochschule München. Listening to the very inspiring physics lectures by Jonathan Zenneck with lots of demonstrations - 6 full hours a week - I felt being on the right track.

After my first examination in 1934 I turned to the Technische Hochschule in Berlin. I was lucky in finding in Hans Kopfermann a teacher with a feeling for the essentials in physics but also a very liberal man, who had taken a fatherly interest in me. He, a former Ph.D. student of James Franck, had just returned from a three years stay at the Niels Bohr Institute in Copenhagen, working in the field of hyperfine spectroscopy and nuclear moments. All in all I worked 16 years with him.

As a theorist Richard Becker taught at the TH Berlin whom I met later at the University of Göttingen again. Both men had the strongest influence on my scientific thinking. But it was not only the scientific aspect. In the Germany of these days just as important was the human and the political attitude. And I am still a little bit proud having been accepted by these sensitive men in this respect. Here are the roots for my later engagement in the anti nuclear weapon discussion and for having signed the declaration of the so-called "Göttinger Eighteen" in 1957 with its important consequences in german politics.

In 1937 after my diploma exam with Hans Geiger as examinator I followed Kopfermann to the University of Kiel where he had just been appointed Professor Ordinarius. For my doctor thesis I had chosen the determination of the nuclear moments of Beryllium from the hyperfine spectrum. I developed an atomic beam light source to minimize the Doppler effect. But just before the decisive measurements I was drawn to the air force a few days before the war started. Fortunately, a few month later I got a leave of absence to finish my thesis and to take my doctor exam at the TH Berlin. In 1940 I was exempted from military service. I joined again the group around Kopfermann which 2 years later moved to Gottingen. There in 1944 I became Privatdozent at the University.

In these years I worked in mass spectrometry and isotope separation together with W. Walcher. When we heard of the development of the betatron by D. Kerst in the United States and also of a similar development by Gund at the Siemens company, Kopfermann saw immediately that scattering experiments with high energy electrons would enable the study of the charge structure of nuclei. He convinced me to turn to this new very promising field of physics and I soon participated in the first test measurements at the 6 MeV betatron at the Siemens laboratory. Later after the war we succeeded in getting this accelerator to Gottingen.

But due to the restriction in physics research imposed by the military government I turned for a few years my interest to radiobiology and cancer therapy by electrons in collaboration with my colleague G. Schubert from the medical faculty.

Besides we performed some scattering experiments and studied first the electric disintegration of the deuteron, and not to forget for the first time we measured the Lamb shift in the He-spectrum with optical methods.

In 1952 I was appointed Professor at the University of Bonn and Director of the Physics Institute, with very good students waiting for a thesis advisor. I was very lucky that my best young collaborators followed me 0. Osberghaus, H. Ehrenberg. H.G. Bennewitz, G. Knop and H. Steinwedel as a "house theoretician". Here we started new activities: molecular beam physics, mass spectrometry and high energy electron physics. It was a scanty period after the war. But in order to become in a few years competitive with the well advanced physics abroad we tried to develop new methods and instruments in all our research.

In this period these focusing methods in molecular beam physics with quadrupole and sextupole lenses having already started in Gottingen with H. Friedburg, were further developed and enabled new types of experiments. The quadrupole mass spectrometer and the ion trap were conceived and studied in many respects by research students. And with the generous support of the Deutsche Forschungsgemeinschaft we have built a 500 MeV electron synchrotron, the first in Europe working according to the new principle of strong focusing. It was followed in 1965 by a synchroton for 2500 MeV. My colleagues H. Ehrenberg, R.H. Althoff and G. Knop were sharing this success with me.

In recent years my interest turned to neutron physics with a new device, a magnetic storage ring for neutrons.

U. Trinks and K.J. Kügler and later my two sons Lorenz and Stephan, joined me in our experiments with stored neutrons at the ILL in Grenoble. My experience in accelerator physics brought me in close contact to CERN. I served there from the very early days on as an advisor. Having spent the year 1959 in Genève I became director of the nuclear physics division for the years 1964 - 67. I was for several years member and later chairman of the Scientific Policy Committee and for many years scientific delegate of Germany in the CERN-Council. For a short period I was chairman of ECFA, the European Committee for Future Accelerators.

Together with my friends W. Jentschke and W. Walcher in 1957 we started the German National Laboratory DESY in Hamburg which I joined as chairman of the directorate 1970 - 73. For several years I was chairman of its scientific council. In the same positions I served in the first years of the Kernforschungsanlage Jülich.

In 1970 I spent some weeks as Morris Loeb lecturer at Harvard University. 1978 I was lecturing as distinguished scientist at the FERMI Institute of the University of Chicago and in a similar position at the University of Tokyo. Since 1981 I am Professur Emeritus at the Bonn University.

In the past decades of recovery of German Universities and Physics research I was engaged in many advisory bodies. I have served as a referee and later as member of senate to the Deutsche Forschungsgemeinschaft. I was member and chairman of several committees: for reforming the university structure and for research planning of the federal government.

Ten years ago I was elected President of the Alexander von Humboldt Foundation which since 130 years fosters the international collaboration among scientists all over the world in the universal spirit of its patron Humboldt.

I was married for 36 years to the late Liselotte Paul, nee Hirsche. She shared with me the depressing period during and after the war and due to her optimistic view of life she gave me strength and independence for my profession. Four children were born to us, two daughters, Jutta and Regine, an historian of art and a pharmacist, and two sons, Lorenz and Stephan, both being physicists. Since 1979 I am married to Dr. Doris Walch-Paul, teaching medieval literature at the University of Bonn.