Experimental investigation of ≈130 keV kinetic energy antiprotons annihilation on nuclei

The recent observation of single spins flips with a single proton in a Penning trap opens the way to measure the proton magnetic moment with high precision. Based on this success, which has been achieved with our apparatus at the University of Mainz, we demonstrated recently the first application of the so called double Penning-trap method with a single proton. This is a major step towards a measurement of the proton magnetic moment with ppb precision. To apply this method to a single trapped antiproton our collaboration is currently setting up a companion experiment at the antiproton decelerator of CERN. This effort is recognized as the Baryon Antibaryon Symmetry Experiment (BASE). A comparison of both magnetic moment values will provide a stringent test of CPT invariance with baryons.     

The gyromagnetic ratio of the 589 keV 3/2− state of117In

Theg-factor of the 589 keV state of¹¹⁷In has been determined by a measurement of the rotation of the 1,303–273 keVγ —γ directional correlation in an external magnetic field of 9.55(1) T. The result,g _3/2(589 keV)=+0.068(39), contradicts the usual interpretation of the state as the 2p _3/2 single proton hole configuration for which the Schmidt value isg _3/2-(Schmidt)=+2.53. It favours the interpretation as the first rotational state built up on the single proton [301] 1/2^? Nilsson orbit in a strongly deformed core of prolate shape.     

Spectroscopy of the hyperfine structure of antiprotonic 4He and 3He

The spin magnetic moment $\mu^{\overline{p}}_{s}$ of the antiproton can be determined by comparing the measured transition frequencies in $\overline{p}^4$ He^?+? with three-body QED calculations. A comparison between the proton and antiproton can then be used as a test of CPT invariance. The highest measurement precision of the difference between the proton and the antiproton spin magnetic moments to date is 0.3%. A new experimental value of the spin magnetic moment of the antiproton was obtained as $\mu^{\overline{p}}_{s} = -2.7862(83)\mu_{N}$ , slightly better than the previously best measurement. This agrees with $\mu^{p}_{s}$ within 0.24%. In 2009, a new measurement with antiprotonic ³He has been started. A comparison between the theoretical calculations and experimental results would lead to a stronger test of the theory and address systematic errors therein. A measurement of this state will be the first HF measurement on $\overline{p}^3$ He^?+?. We report here on the new experimental setup and the first tests.     

A Novel Penning‐Trap Design for the High‐Precision Measurement of the 3He2 + Nuclear Magnetic Moment

A new experiment is constructed aiming at the first direct high‐precision measurement of the helium‐3 nuclear magnetic moment with a relative precision of parts‐per‐billion or better. Methods similar to those used in proton and antiproton magnetic moment measurements are applied. As those techniques rely on the challenging detection of single spin‐flips, a novel Penning trap design optimized for nuclear spin‐flip detection is developed.     

The magnetic moment of the lowest 3/2− state in57Co

The reaction⁵⁴Fe(α, n)⁵⁷Ni has been used to implant⁵⁷Co isotopes in ferromagnetic iron. Theg-factor of the lowest 3/2^? state is determined using the internal field in a constant angle reversed field method. The angular correlation of the 127–1,378 keV cascade is also measured. The result of the angular correlation measurement together with reaction data is consistent withp _3/2 andp _1/2 single particle assignments to the lowest 3/2^? resp. 1/2^? state. In view of this statement the quenching of the magnetic moment is discussed.     

Mass and magnetic moment of the antiproton by the exotic atom method

Precision determinations of the mass and magnetic moment of the antiproton were made by the exotic atom method. Antiprotons were stopped in lead or uranium targets. De-excitation X-rays from the antiprotonic atoms were viewed by a high resolution Ge (Li) detector. Six principal transitions of the p?Pb spectrum (16 → 15 to 11 → 10) were analyzed to deduce a value of the antiproton mass. The fine structure splittings of the 11 → 10 and 12 → 11 transitions of p?Pb and p?U were used to determine a value of the antiproton magnetic moment. Our computed values of the energy eigenvalues of the (n, l, j) levels included corrections due to vacuum polarization and higher order radiative terms, electron screening, nuclear finite size and nuclear polarization. In the case of the p?U data, an additional shift due to the dynamic E2 mixing of nuclear rotational levels with antiprotonic orbital levels was included. Noncircular transitions were included in the analysis of the data. The values obtained for the antiproton mass and magnetic moment, 938.179±0.058 MeV and ? 2.791±0.021 nuclear magnetons, respectively, are compared with the corresponding quantities pertaining to the proton, 938.2796 ± 0.0027 MeV and +2.793 nuclear magnetons, respectively (error 1.1 × 10^?6 nuclear magnetons).     

Direct measurement of the proton magnetic moment

The proton magnetic moment in nuclear magnetons is measured to be μ(p)/μ(N) ≡ g/2 = 2.792?846 ± 0.000?007, a 2.5 parts per million uncertainty. The direct determination, using a single proton in a Penning trap, demonstrates the first method that should work as well with an antiproton (p) as with a proton (p). This opens the way to measuring the p magnetic moment (whose uncertainty has essentially not been reduced for 20 years) at least 10(3) times more precisely.     

Magnetic moment and electric quadrupole moment of the anomalous186Ir ground state

The ground state nuclear moments of¹⁸⁶Ir (j ^π=5⁽⁺⁾) have been determined with NMR on oriented¹⁸⁶Ir in Ni as |μ|=3.80 _?0.02 ^+0.12 μ _n andQ=?3.00 (15)b. The quadrupole moment is consistent with an anamolousj ^π K=5⁺0 or 5⁺1 ground state configuration. The explanation of the magnetic moment in terms of pure 5⁺0 or 5⁺1 configurations would require a high collectiveg _R-factor ofg _R≧0.76. On the other hand the magnetic moment can be explained with a “normal”g _R and a mixed ground state configuration.     

Average g-factors for high-spin states in 78Kr

Inverse reactions of ^{63, 65}Cu beams on ^{18, 16}O targets have been used to populate states of ⁷⁸Kr by fusion-evaporation reactions. The excited nuclei recoiled at high velocity v/c ≈ 7 % through a polarized iron (⁵⁴Fe) layer and were stopped in a copper layer. During the period in iron, 0.05–0.65 ps, the nuclei were subjected to the intense transient magnetic field (initially ～ 3500 T). The resulting precession of the high-spin nuclear states populated during this time was determined by measuring the time integral rotation angle of the discrete γ-ray transitions at low spin.The average g-factor at low spin 2 ≦ J ≦ 8 compared to that at higher spin 8 ≦ J ≦ 12 in ⁷⁸Kr was found to be identical within the experimental uncertainties of ～ 15 %. This result implies that either there are no rotational alignment effects at the backbend in ⁷⁸Kr or more plausibly, proton (g ≈ 1) and neutron (g ≈ 0) aligned bands are equally competitive and both populated in the reaction. It is then likely that the resulting g-factor represents an average over many populated proton and neutron aligned bands.     

Magnetic moment of the 1,307 keV state in69As

The Larmor precession of the 1,307 keV 2 ns state in⁶⁹As in an external magnetic field of 2 T has been observed in a time integral perturbed angular distribution experiment. The deducedg-factor ofg=1.05±0.13 confirms the rather pureg _9/2 proton structure of this state on which a triaxial rotational aligned band is built.     

Dependence of electron spin g-factor on magnetic field in quantum wells

The dependence of electron spin g-factor on magnetic field has been investigated in GaAs/AlGaAs quantum wells. We have estimated the electron g-factor from spin precession frequency in time-resolved photoluminescence measurements under a magnetic field in different configurations; the magnetic field perpendicular (g_⊥) and parallel (g_∥) to the quantum confinement direction. When the angle between the magnetic field and the confinement direction is 45°, we have found that g-factor varies depending on the direction of magnetic field and the circular polarization type of excitation light (σ⁺ or σ^?). These dependences of g-factor exhibit main features of Overhauser effect that nuclear spins react back on electron spin precession. The value of g_⊥ and g_∥ corrected for the nuclear effects agree well with the results of four-band k·p perturbation calculations.     

Frequency modulation of the 6.2 keV Mössbauer states of181Ta

Mössbauer sidebands up to the first order from a single parent line have been produced by subjecting a non magnetic W(¹⁸¹W) Mössbauer source to a strong oscillating magnetic field of up to 230 Oe amplitude and a frequency of about one megahertz. The sidebands positions and intensities agree very well with theory, which is based on a periodic time-dependent interaction of the magnetic field with the nuclear magnetic moments of ground and excited states, respectively. From the sideband intensity ag-factor ratio ofg _e /g _g =1.75(6) was derived.     

The magnetic moment of the 4+, 3.55 MeV level of 18O

The magnetic moment of the 4⁺, 3.55 MeV level of ¹⁸O has been determined to be |g| = 0.62 ± 0.10 in a perturbed angular correlation measurement on nuclei recoiling into gas and vacuum. Analysis of the recoil-into-gas data using the Abragam-Pound model agrees with analysis of the recoil-into-vacuum data using a model for the electronic ensemble described in a previous communication. The value of the g-factor shows the 4⁺ wave function to consist mainly of the$\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^2$ configuration.     

Magnetic moments of the anomalous parity 52+ 13.3 keV state of 73Ge

The g-factor of the $\text{3 μs}\text{5}\text{2}$⁺ level in ⁷³Ge was determined to be g=?0.0376±0.0010 by the time-differential perturbed angular correlation method. The magnetic moment of the anomalous parity state is discussed on the basis of the extended quasiparticle-phonon coupling model.     

EPR of a fullerene-molecule-derived paramagnetic center as a mesoscopic conducting object

Discussion of theg-factor value of fullerene is based on the model of itinerant electrons restricted to the surface of the fullerene molecule C₆₀. The Ag shift, i.e., the difference between the experimentalg-factor and theg-factor of free electron Δg = g ? 2.0023 for C ₆₀ ^?1 is negative as for a very small metallic conducting particle.g-factor value is proportional to the interaction between itinerant electrons in the conduction band, thus the Δg is negative for C ₆₀ ^?1 and C ₆₀ ^?3 having less than half filled conduction band, while Δg is positive for C ₆₀ ⁺ where the conduction band is almost filled.     

Magnetic moment of the 10−, 2.53 ms state in 208Bi measured by in-beam NMR-PAD

The g-factor of the 10^? isomeric state in ²⁰⁸Bi has been measured by the method of inbeam NMR-PAD. From the experimental value $\text{¦g¦= 0.2666(27)}$ the magnetic moment of the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ neutron hole state is deduced. The result is compared with experimental values of neighbouring nuclei and theoretical predictions.     

The effects of vibration-rotation on the quadrupole moment,rotational g-factor and spin-rotation parameters of the water molecule

Ab initio SCF surfaces for the quadrupole moment, rotational g-factor and spin-rotation parameters of the water molecule have been obtained from the magnetizability and nuclear shielding surfaces. Values of these properties in low vibration-rotation states of the more important isotopomers are presented.

Vibrational averaging (with an accurate empirical force field) brings calculated values to within 1 per cent of experimental values for the quadrupole moment components and 3 per cent for the g-tensor components. Substantial vibrational effects on the proton, deuteron and ¹⁷O spin-rotation parameters are predicted but the calculated values differ significantly from experiment. This is attributed to inadequacy of the SCF calculation of paramagnetic shielding.     

New determination of the magnetic moment of the54Fe(2 1 + ) state at 1.408 MeV

Relative to the wellknowng-factor of⁵⁶Fe(2 ₁ ⁺ ) at 0.847 MeV, theg-factor of the⁵⁴Fe(2 ₁ ⁺ ) state at 1.408 MeV has been remeasured employing the technique of transient magnetic fields (TF) with the ions slowed down in ferromagnetic Gd host at initial velocities of 2.5 ν₀. Coulomb excitation on beams of^54,56Fe was accomplished with a Si target. The value obtained,g=1.05(17), is in excellent agreement with two previous results but disagrees with the value from a TF measurement where the ions passed through ferromagnetic Fe.     

Observation of knight shifts in metallic tungsten and tantalum with the 6.2 keV181Ta Mössbauer resonance

Completely resolved Mössbauer spectra for the 6.2 keV¹⁸¹Ta transition were measured at R.T. in external magnetic field of 2.8 and 4.4 kOe for¹⁸¹Ta impurities in W- and Tametal respectively. A more precise mean value for theg-factor ratiog _9/2/g _7/2 of 1.797(3) was obtained. The magnetic moment of the 6.2 keV-state was determined to be +5.47 (2) n.m. From the hyperfine fields at the¹⁸¹Ta-nuclei in W a Knight-shift of 2(1)% and in Ta of 1.7(8)% was deduced. For the spectrum of the magnetically splitted Ta-metal absorber a reduced dispersion parameter of 2ξ=20(2) was measured, while the linewidth showed only a slight narrowing.     

Oscillations of the photon echo intensity in a pulsed magnetic field: Zeeman splitting in LiLuF<Subscript>4</Subscript>:Er<Superscript>3+</Superscript>

A method of high-resolution time-resolved optical spectroscopy using oscillations of the photon echo intensity in the presence of a perturbation, which splits the optical frequencies of the transitions of two or more ion subgroups, has been proposed and demonstrated. This method has been applied to systems in which the Zee-man effect is manifested. The transition frequencies of ions are switched by a pulsed magnetic field. Oscillations of the photon echo intensity were observed in LiLuF₄:Er³⁺ and LiYF₄:Er³⁺. The first minimum corresponding to the accumulated phase of the electric dipole moment π/2 is reached in the pulsed magnetic field with an amplitude of ～2 G at a duration of 30 ns. The Zeeman splitting in this field is ～10 MHz, which is much less than the laser spectral width (0.15 Å ～ 9 GHz). The g factor of the ⁴ F _9/2(I) excited state of the Er³⁺ ion in the LiLuF₄ matrix has been determined in zero magnetic field. The comparison with the g-factor value found from the measurement of the absorption spectrum in a magnetic field of 8 kG has been performed.