Hans Dehmelt

Principles of the stored ion calorimeter

The properties of a harmonically bound radiatively thermalized ion gas were investigated by studying the behavior of an electron cloud stored in a Penning trap. A simple model characterizing ions contained in an electromagnetic trap is proposed and tested by investigating the electromagnetic−dynamic behavior of these electrons subject to various external perturbations. The ion calorimeter realized in such a system is also discussed; particular attention is devoted to sensitivity to heat inputs into the various degrees of freedom.

Past Electron-Positron g − 2 Experiments Yielded Sharpest Bound on CPT Violation for Point Particles

In our past experiments on a single electron and positron we measured the cyclotron and spin-cyclotron difference frequencies omega_c and omega_a and the ratios a = omega_a/ omega_c at omega_c = 141 Ghz for e^- and e^+ and later, only for e^-, also at 164 Ghz. Here, we do extract from these data, as had not done before, a new and very different figure of merit for violation of CPT symmetry, one similar to the widely recognized impressive limit |m_Kaon - m_Antikaon|/m_Kaon < 10^-18 for the K-mesons composed of two quarks. That expression may be seen as comparing experimental relativistic masses of particle states before and after the C, P, T operations had transformed particle into antiparticle. Such a similar figure of merit for a non-composite and quite different lepton, found by us from our Delta a = a^- - a^+ data, was even smaller, h_bar |omega_a^- - omega_a^+|/2m_0 c^2 = |Delta a| h_bar omega_c/2m_0 c^2) < 3(12) 10^-22.

Trapping and thermalization of positrons for geonium spectroscopy

Abstract A static technique for continuously catching positrons in a Penning trap under ultra-high vacuum conditions has been demonstrated and a preliminary measurement of the positron/electron mass ratio was made yielding m(e+)/m(e)- = 1 ± 1.3 × 10−7.

High mass resolution with a new variable anharmonicity Penning trap

A modified Penning trap has been developed and shown to yield 100 times narrower axial resonance linewidths on electrons than that of a previous unmodified Penning trap. An extra pair of electrodes is inserted in the standard trap configuration, which effectively nulls the quartic term in the trapping potential. With existing signal‐to‐noise limitations, an axial frequency resolution of 0.02 ppm can be obtained. This device is particularly attractive to high‐resolution mass spectrometry.

Doppler-free optical spectroscopy on the Ba + mono-ion oscillator

Laser fluorescence spectroscopy has been performed on the two-photon 62S1/2 to 52D3/2 transition in Ba+. Using signals from an individual laser-cooled ion in a rf trap, a laser limited linewidth of less than 3 MHz has been achieved with an effective wavelength of 2.07 μm. The absence of any sidebands in the spectra spaced at the 5.5-MHz oscillation frequency of the ion in the rf quadrupole trap indicates that the ion vibrational motion must be well into the Lamb–Dicke regime. An upper limit of 165 nm is given to the vibrational amplitude.

Demonstration of new Paul–Straubel trap for trapping single ions

New Paul–Straubel traps [H. Straubel, Naturwissenschaften 18, 506 (1955)] have been recently constructed and used to trap single Ba+ ions. Unlike a conventional rf trap, these traps use only a ring electrode surrounded by an uncritical ground electrode structure. The overall simplicity makes it easy to miniaturize the trap and to control the trapping potential spatial orientation. The new design also allows intense heating of the ring electrode with an ion in the trap simply by passing a large current through it. This removes surface layers responsible for large contact potentials varying over the ring surface and greatly reduces the forced micromotion of the ion, which is supposedly ‘‘at rest.’’

Axial, magnetron, cyclotron and spin-cyclotron-beat frequencies measured on single electron almost at rest in free space (geonium)

THE monoelectron oscillator1 consists of a ∼ 1-meV electron contained in a weak electric quadrupole field plus strong axial magnetic field (the Penning trap) on which the axial oscillation is continuously observable. It may profitably be looked on as an ultraheavy metastable pseudoatom, ‘geonium’ (through the trap and the magnet, the electron is bound to the Earth ultimately). The energy levels are given by2 with v c = eH/2πmc, 2v c v m − 2v m 2 = v z 2. We report here the measurement of the axial, magnetron, cyclotron, and spin-cyclotron-beat frequencies v z , v m , v c − v m and v s −v c +v m using this apparatus, held at 4K. A new axial-frequency-shift technique using a 30-gauss deep magnetic bottle superimposed on the 18-kgauss field supplied by a superconducting magnet was used for the last two frequencies. The road to this advance was paved by two developments, namely the anharmonicity compensated trap3 yielding an axial line width of 10−7 and the “entropy reduction by motional sideband excitation” (ref. 4) method. The latter allows the centring of an electron liberated in the trap to close tolerance guaranteeing the constancy of v z .

High resolution Ba+ monoion spectroscopy with frequency stabilized color-center laser

Abstract We describe an experiment in which a stabilized color-center laser is used to perform high resolution spectroscopy on single, laser-cooled barium ions. Virtually every transition between the two levels of interest was observed using the “shelved-optical electron” double resonance technique. Detailed error signal analyses show a 4.8 kHz rms laser linewidth relative to the reference cavity. The absolute laser linewidth can be determined from the single ion spectrum, where the single ion can be viewed as an extremely narrow, stable spectrum analyzer. Correcting for slow cavity drift, an rms laser linewidth of ≃ 13 kHz over a 10 s observation period is obtained. We believe that the observed absolute laser with is principally limited by short term fluctuations in the reference cavity.

Stored-Ion Spectroscopy

An individual elementary/atomic particle kept at rest in free space for extended periods, is an ideal object for high resolution spectroscopy. All external causes for line broadening or shifts such as 1. and 2. order Doppler and transit time effects as well as Zeeman or Stark effects are eliminated for such a system. This ideal has been approximated most closely so far in experiments on an individual Ba+ ion localized in a Paul (rf) quadrupole trap to ∿2000A by optical side band cooling and made visible, all accomplished by means of laser Open image in new window Fig. 1. Mono-electron oscillator mode of electron in Penning trap, the Geonium “atom.” The electron moves only parallel to the magnetic field →B and along the symmetry axis of the electrode structure. Each time it gets too close to one of the negatively charged caps it is turned around and an oscillatory motion results. beams. High resolution spectroscopy on an individual electron/positron localized to <200 µm by rf side band cooling in a Penning trap employing a 50 kG field has already yielded the most precise data on the magnetic moments of these particles and also provided a severe test of the CPT theorem for charged elementary particles. Furthermore, localization of an elementary particle in space is one of the most fundamental problems in physics and worthy of study on its own merit.

Geonium spectra⋅electron radius⋅cosmon

By means of a new, continuous version of the Stern‐Gerlach effect the g‐factor of the electron, an elementary particle as simple as a quark, has been measured to 4 parts in 1012. After QED corrections, this g‐factor deviates from the Dirac value 2 by ≊10−10. A graph of corrected measured non‐Dirac contributions ‖g–2‖ vs normalized radius for the three next larger stable charged near‐Dirac fermions, proton, triton, and 3He nucleus, when applied to the electron, then suggests an rms radius R〈10−20 cm. The graph further suggests a progression of ever smaller, heavier and less imperfect near‐Dirac particles, until ‘‘the’’ elementary particle, the ‘‘cosmon’’ is reached. A lone ‘‘cosmon/anticosmon’’ pair, bound so tightly that its relativistic mass is zero, is assumed to have been formed from the metastable vacuum in a spontaneous quantum jump. Rapid disintegration of cosmon and anticosmon, each of immense mass, then formed the early universe in the big bang. No infinitely small point particles or singularities...