P. Merz

A test of special relativity with stored lithium ions

Laser spectroscopy at the heavy ion storage ring TSR in Heidelberg allows for precision experiments testing the limits of the special theory of relativity. With an opticalΛ-type three-level system of7Li+ the Doppler shift has been measured by saturation spectroscopy as a test of the time dilatation factor γ = (1 −β2)−1/2 at an ion velocity ofυ = 6.4% c. A precision ofΔν/ν < 9 × 10−9 has been obtained, which sets a second-order limit of 1.1 × 10−6 for any deviation from the time dilatation factor. The fourth-order limit of this deviation is set below 2.7 × 10−4 by the present experiment. These limits are given at a 1 σ confidence level.

Precision measurement of two iodine lines at 585 nm and 549 nm

The transition frequencies of thei-component of the R(99)15-1 and thew-component of the R(85)26-0 transition in the B-X system of molecular127I2 have been determined with an overall relative standard uncertainty of 1.3 · 10−10. For this purpose a commercial linear dye laser has been modified and stabilized to the corresponding iodine line. This dye laser serves as a transportable frequency standard which is compared with the wavelength standards of the PTB. The evaluation of an experiment for testing special relativity at the test storage ring (TSR) in Heidelberg is based on the precision of the reported interferometric wavelength comparison.

TRANSVERSE LASER COOLING OF A RADIO-FREQUENCY BUNCHED ION BEAM IN THE STORAGE RING TSR

Abstract We report on the observation of the indirect transverse laser cooling effect in a radio-frequency bunched beam of 7.3 MeV 9 Be + ions, stored in the Heidelberg Test Storage Ring and subject to direct longitudinal laser cooling. This bunched scheme offers particular advantages for producing ultracold beams with unprecedented phase-space densities.

Test of special relativity in an ion storage ring

An accurate measurement of the Doppler effect in collinear laser spectroscopy has been performed at the TSR storage ring with electron cooled7Li+ ions atΒ=0.064. This experiment is a sensitive test of theγ=(1−Β2)−1/2 factor(Β=v/c) in the special theory of relativity. The Doppler shifted frequencies of the moving7Li+ ions are compared with calibrated molecular lines at rest. The frequencies at rest for the7Li+ ions are known from independent measurements. The Doppler shifted frequencies in the collinear experiment have been measured with a precision ofδv/v=6×10−9, mainly limited by the signal width of the resonance. A corresponding upper limit of 8×10−7 is deduced for any deviation of the time dilatation factorγ in special theory of relativity. A still higher accuracy is expected with a laser cooled ion beam. If such a beam is simultaneously subjected to RF bunching, the particle velocity and phase are exactly known. With an additional high resolution laser frequency measurement an improvement of at least one order of magnitude may be achieved.

Laser spectroscopy of the 1s HFS of H-like ions at a bunched beam in the storage ring ESR

The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics from an ion beam at relativistic velocities.

New access to the magnetic moment distribution in the nucleus by laser spectroscopy of highly charged ions

Abstract The availability of high intensity, high quality beams of highly charged ions has started a new application for laser spectroscopy. High resolution spectroscopy can now be applied to a study of hydrogen-like atomic states in heavy elements. In principal, this will allow a determination of the hyperfine splitting with an accuracy in the 10 −6 -range or better. Presently this exceeds the limits given by the uncertainties of the nuclear quantities, especially the distribution of the nuclear magnetization in the nucleus. Since the new approach can be applied to a family of test cases, it can provide a wide experimental basis for the separation of nuclear and QED effects. This is especially true since measurements of the hyperfine splitting have now also been performed at the Super-EBIT ion trap. For the determination of nuclear parameters it will be of benefit to measure more candidates close to the doubly magic 208 Pb. In such systems theoretical efforts to clarify details of the nuclear structure and of the interaction between the nucleus and the electron can be expected to even surpass the present experimental accuracy.

Bunched laser cooling of a stored weak 7Li+ ion beam in a pure triplet state

A preparation scheme for a 7Li+ ion beam in a storage ring is presented which provides ions in the metastable triplet states with well controlled longitudinal phase space properties. For both state selective preparation and beam cooling, laser- and electron-cooler forces are applied. The spatial- and momentum distributions of the ions are directly detected by a time resolved measurement of the fluorescence light. At low beam intensities, the remaining heating rate of such a beam is completely determined by residual gas scattering.

Ion beam preparation of 7Li+ for precision experiments at heavy ion storage rings

Abstract Heavy ion storage rings allow for tests of the structure of local space time via the Doppler effect. At the TSR/Heidelberg an experiment with high resolution laser spectroscopy at 7 Li + is performed. To gain the maximum resolution for saturation spectroscopy new methods of relativistic ion beam preparation and diagnostics have been developed. The laser cooling of the beam allows for precision determination of the mean velocity of the ions. A novel phase synchronous detection scheme, ultimately sensitive to single ions, gives insights into the cooling mechanism and dynamics. With an additional synchronous excitation scheme systematic uncertainties of the test experiment can be drastically reduced. After separation of the ground state ions from the triplet states of 7 Li + by the combination of laser and electron cooling, a bunched and cooled ensemble of fast moving high precision clocks with minimized perturbations by space charge effects and intra beam scattering is available.

Preparation of relativistic 7Li+ ion beams for precision experiments at storage rings

Heavy ion storage rings allow for tests of the structure of local space time via the Doppler effect. At the TSR/Heidelberg an experiment with high resolution laser spectroscopy at 7Li+ is performed. To gain the maximum resolution for saturation spectroscopy new methods of relativistic ion beam preparation and diagnostics have been developed.The laser cooling of the beam allows for precision determination of the mean velocity of the ions. A novel phase synchronous detection scheme, ultimately sensitive to single ions, gives insights into the cooling mechanism and dynamics. With an additional synchronous excitation scheme systematic uncertainties of the test experiment can be drastically reduced. After separation of the ground state ions from the triplet states of 7Li+ by the combination of laser and electron cooling, a bunched and cooled ensemble of fast moving high precision clocks with minimized perturbations by space charge effects and intra beam scattering is available.

Laser spectroscopy with a cooler ring at the esr (GSI) and the TSR (MPI Heidelberg)

At the TSR cooler ring at Heidelberg, laser studies were carried out using singly charged lithium and beryllium ions. Laser spectroscopy of relativistic lithium ions (v=0.04c) yielded signals with a narrow linewidth, suitable for an experimental test of special relativity. A dramatic reduction of the beam temperature, as defined by the longitudinal velocity spread, was achieved via laser cooling in both cases. At the ion energies available at ESR it will become possible to prepare and store bare ions up to U92+. Electron cooling was succesfully demonstrated for hydrogen-like Bi82+ ions, where a laser experiment is scheduled to study the ground-state hyperfine splitting.