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H Dehmelt

Publications and source records attributed to H Dehmelt.

At least 19 recordsLinked to original sources
PubMed1997

Paul-Straubel-Kingdon trap for true zero-point confinement of an individual ion and reservoir.

A modification of the Paul-Straubel trap previously described by us may profitably be operated in a Paul-Straubel-Kingdon (PSK) mode during the initial loading of an individual ion into the trap. Thereby the coating of the trap ring electrode by the atomic beam directed upon it in earlier experiments is eliminated, as is the ionization of an already trapped ion. Coating created serious problems as it spot-wise changed the work function of the ring electrode, which caused large, uncontrolled dc fields in the trap center that prevented zero-point confinement. Operating the Paul-Straubel trap with a small negative bias on the ring electrode wire is all that is required to realize the PSK mode. In this mode the tiny ring trap in the center of the long, straight wire section is surrounded by a second trapping well shaped like a long, thin-walled cylindrical shell and extending to the end-caps. There, ions may be conveniently created in this well without danger of coating the ring with barium. In addition, the long second well is useful as a multi-ion reservoir.

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PubMed1996

Excitation transfer spectroscopy with two metastable 138Ba+ ions in same trap.

In the absence of lasers approaching trapped ion clock transitions in sharpness we propose to replace the 12.49 m laser field exciting the D3/2-D5/2 transition of the single Ba+ ion A in D3/2 with the near-field of a close by identical ion B in the excited D5/2 state. We tune the frequency of the near-field by the differential Stark shift generated when the center of mass of the tuned ions is slightly moved out of the trap center by a small bias voltage. We demonstrate that the resultant resonant energy exchange can be made considerably faster than the natural lifetime of either metastable level and show how it might be detected.

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PubMed1994

Trapped electron cloud bolometer relying on frequency shift.

An improved electron cloud bolometer is analyzed. In this device the cloud temperature is read out not via thermal noise induced by the electrons in a coupled LC circuit but via shift in their axial oscillation frequency in the Penning trap confining them. This shift occurs because as the electron cloud expands with increasing temperature, the average restoring force in the slightly anharmonic trap does change perceptibly. The scheme will be useful in exploring the microwave mode structure of the trap cavity and in locating magnetic field values for which the cavity-induced shift in the measured electron g factor disappears.

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PubMed1994

Zero-shift tuning in geonium by variation of trapped charge.

Measuring the g factor, or gyromagnetic ratio of an individual electron or positron permanently confined in ultrahigh vacuum at liquid helium temperature, provides one of the few avenues for testing the currently accepted standard model that views these elementary particles, on the same level as the quarks, as point-like objects without internal structure. Our results, even though their error limits are the smallest ever attained, would still benefit by possibly two orders of magnitude if a shift, estimated at 4 parts in 10(12), caused by interaction of the cyclotron motion with standing electromagnetic waves in the trap cavity confining the electron could be eliminated. Reexamination of experimental data obtained in another connection suggests that it is practical to identify certain critical cyclotron frequency values for that the shift disappears by testing if the cyclotron frequency measured on a cloud of electrons does not vary with the number of electrons it contains. Clouds here must be kept very much smaller than the wavelength of the above standing waves.

Cyclotrons↗
PubMed1992

The 31S0-33P0 transition in the aluminum isotope ion 26A1+: a potentially superior passive laser frequency standard and spectrum analyzer.

The aluminum 26 isotope ion is proposed here as a possible candidate for a superior atomic clock. For this even isotope, the extraordinarily long lifetime of the 33P0 state offers a potential clock transition (31S0-33P0) linewidth of 300 microHz. The mF = 0 --> 0 transition has only a quadratic Zeeman shift approximately 4 x 10(-18) at 0.1 Gauss magnetic field, compared to approximately 10(-8) for the hydrogen maser. Electronic quadrupole moments vanish for both J and J' states and with them shifts due to electric field gradients. All shifts have been estimated and are orders of magnitude less than for Hg+ and Ba+, which are being studied as atomic clock elements.

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PubMed1992

Monitoring electron spin by running geonium atom as microaccelerator.

Following the classic work of McMillan and of Bohm and Foldy, we have developed a phase equation describing the microsynchrocyclotron acceleration process in geonium. By computer integration of this equation, we are able to confirm that, by making use of the slight relativistic spin dependence of the zero-energy cyclotron frequencies, the acceleration process can be made selective enough to distinguish between spin-up and spin-down states. Quantum effects have been allowed for approximately.

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PubMed1992

Practical zero-shift tuning in geonium.

Compositeness of the electron may show up in a very small deviation of the measured electron g factor from one calculated for a point electron by quantum electrodynamics. The precision of our g measurements is currently limited by an interaction of the cyclotron motion with standing waves in the trap cavity containing the electron. The important element introduced here is the systematic exploration of the trap cavity modes and the electron's coupling to them by measuring the shifted electron g factor gc = gc(omega e) as a function of the cyclotron frequency omega e. By measuring gc values at five different omega e values and modeling the trap cavity by six lumped LC circuits, the L values for the four most important modes may be determined and finally the unshifted g value may be extracted. Auxiliary experiments are relied upon only for the L values of the two least critical cavity modes. By designing the trap as a high-Q microwave cavity, an electron cyclotron and anomaly resonance linewidth one or even two orders of magnitude narrower than in free space may be approached without introducing appreciable frequency shifts.

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PubMed1991

Geonium "K" experiment using spin dependency of cyclotron frequency supports g data of earlier geonium "S" work.

By substituting the relativistic spin state dependence of the cyclotron frequency for the continuous Stern-Gerlach effect and running the geonium atom as a microsynchrocyclotron accelerator we have detected spin flips of the individual trapped electron. In our initial efforts we have been able to obtain a simple symmetric spin resonance about 4-fold narrower instead of a complex asymmetric one and also to support but not as yet seriously test the result of the earlier geonium "S" work, g/2 = 1. 001 159 652 185 5(40).

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PubMed1989

The 6S(0)-6P(0) transition in thallium isotope ion Tl: A superior atomic clock.

Experimental and theoretical studies of the forbidden J = 0 --> J' = 0 optical transition 6(1)S(0)-6(3)P(0) in the odd Hg isotopes are in the literature. From this work natural width and quadratic Zeeman effect have been estimated for the same line in the isoelectronic, even thallium ion (204)Tl(+), which has a very small nuclear magnetic moment. For the m(F) = 0 --> 0 component a linewidth of <0.01 Hz and a quadratic Zeeman shift <10(-18) at 0.1 Gauss are found, compared to 1 Hz and approximately 10(-8) for the hydrogen maser. Electronic quadrupole moments vanish for both J and J' states and with them shifts due to electric field gradients. All shifts are orders of magnitude smaller than for Hg(+) and Ba(+), which have been studied as atomic clock elements.

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PubMed1989

Trapped individual ion at absolute zero temperature.

Laser cooling and ion trapping have progressed to such an extent that one can now speak of realizing a confined atom at absolute zero temperature. In this short publication, we analyze an experiment toward such realization using a single Ba(+) ion in a miniature rf trap. The Ba(+) ion is first laser-cooled to the limit where the ion spends most of its time in the zero-point energy state. Then a test sequence allows one to verify whether or not the ion is actually in its zero-point state. The test sequence may also serve as a device for state selection of an atom at absolute zero temperature.

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PubMed1989

Miniature Paul-Straubel ion trap with well-defined deep potential well.

In some recently proposed experiments using ion traps, a Paul trap of conventional size and design is insufficient. We have constructed a miniature Paul-Straubel trap. It has a small elliptic ring ( approximately 0.2 mm) and three pairs of planar electrodes ( approximately 2 cm part) arranged so that they form a cube. The two conventional end-cap electrodes are replaced by the six planar electrodes. The ring is heatable to a high temperature for improving the uniformity of the dc potential on the ring surface. With this trap, we hope to do such fundamental studies as the true zero-point confinement of a single ion.

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PubMed1989

Triton,... electron,... cosmon,...: An infinite regression?

I propose an elementary particle model in which the simplest near-Dirac particles triton, proton, and electron are members of the three top layers of a bottomless stack. Each particle is a composite of three particles from the next layer below in an infinite regression approaching Dirac point particles. The cosmon, an immensely heavy lower layer subquark, is the elementary particle. The world-atom, a tightly bound cosmon/anticosmon pair of zero relativistic total mass, arose from the nothing state in a quantum jump. Rapid decay of the pair launched the big bang and created the universe.

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PubMed1988

Relativistic cyclotron resonance shape in magnetic bottle geonium.

The thermally excited axial oscillation of the electron through the weak magnetic bottle needed for the continuous Stern-Gerlach effect modulates the cyclotron frequency and produces a characteristic approximately 12-kHz-wide vertical rise-exponential decline line shape of the cyclotron resonance. At the same time the relativistic mass shift decreases the frequency by approximately 200 Hz per cyclotron motion quantum level n. Nevertheless, our analysis of the complex line shape shows that it should be possible to produce an abrupt rise in the cyclotron quantum number n from 0 to approximately 20 over a small fraction of 200 Hz, when the 160-GHz microwave drive approaches the n = 0 --> 1 transition, and a jump of 14 levels over a frequency increment of 200 Hz has already been observed in preliminary work. This realizes an earlier proposal to generate a very sharp cyclotron resonance feature by quasithermal excitation with a square noise band and should provide a way to detect spin flips when a weak bottle is used to reduce the broadening of the g - 2 resonance by a factor of 20.

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PubMed1988

Metastability transfer spectroscopy with two like ions in the same trap.

High-resolution optical spectroscopy of an individual trapped ion is hampered by lack of sharp lasers. This suggests the use of a second metastable excited ion as an ultrasharp light source. To this end, laser-cool two barium ions to an equilibrium distance of approximately 8 mum on the z (symmetry) axis of the trap and, in this (earth)(Ba(+))(2)-molecule, visually or photoelectrically identify them as A and B by their location. Briefly turn on a 455-nm spectral lamp until one of the ions, say the A ion, is pumped into the metastable D(5/2) level and turns invisible. Focus on the visible, spatially well-resolved B ion and turn off the blue and red illumination lasers for approximately 15 s. Then turn them back on again and check on whether the excitation by chance has been transferred to the B ion and is now in the D(5/2) level and dark while the A ion is bright. The cross section for absorption of the lambda(D(5/2) --> S(1/2)) identical with lambda(0) = 1.76 mum radiation by a stationary ion can be >lambda(0) (2)/2pi. Thus, by pushing the two ions together to approximately lambda(0)/4 by turning on a much stronger trapping field during the excitation exchange period, one might be able to detect excitation transfer in >10% of the attempts. The ions are tuned relative to each other by a 0- to 10-mV/cm variable dc field in the z direction, which displaces them axially and causes them to see different rf fields, which Stark-shifts their frequencies. In this way, a resonant transfer response as sharp as twice the natural width of the D(5/2) level, 11 mHz or a Q approximately 0.4 x 10(17), might be demonstrated.

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