95 research outputs found
Raman velocity filter as a tool for collinear laser spectroscopy
The velocity distribution of a hot ionic beam can be filtered with a narrow
stimulated Raman process to prepare a colder subensemble, as substantiated in
this theoretical analysis. Using two counter-propagating, far-detuned lasers,
we can define a -pulse for the resonant velocity to transfer atoms within
the linewidth of the Raman resonance between the ground-states of a
-system. Spontaneous emission from the two single-photon resonances,
as well as the ground-state decoherence induced by laser noise, diminishes the
efficiency of the filter. From a comprehensive master equation, we obtain
conditions for the optimal frequency pair of the lasers and evaluate the filter
performance numerically, as well as analytically. If we apply this analysis to
current Ca ion experiments, we obtain a sensitivity for measuring
high ion acceleration voltages on the ppm level or below.Comment: Corrected typos. Corrected: Missing minus in Eq. 35. Improved
readability by including a few repetitions of quantity definitions and
improved display of relevant quantities in Table II of the Appendi
Trapped Ion Oscillation Frequencies as Sensors for Spectroscopy
The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called âmagnetic bottlesâ and specific electric anharmonicities creates calculable energy-dependences of the oscillation frequencies in the radiofrequency domain which may be used to detect the absorption or emission of photons both in the microwave and optical frequency domains. The precise electronic measurement of these oscillation frequencies therefore represents an optical sensor for spectroscopy. We discuss possible applications for precision laser and microwave spectroscopy and their role in the determination of magnetic moments and excited state life-times. Also, the trap-assisted measurement of radiative nuclear de-excitations in the X-ray domain is discussed. This way, the different applications range over more than 12 orders of magnitude in the detectable photon energies, from below ÎŒeV in the microwave domain to beyond MeV in the X-ray domain
Nuclear Charge Radius of Be
The nuclear charge radius of Be was precisely determined using the
technique of collinear laser spectroscopy on the transition in the Be ion. The mean square charge radius increases
from Be to Be by \delta ^{10,12} = 0.69(5) \fm^{2}
compared to \delta ^{10,11} = 0.49(5) \fm^{2} for the
one-neutron halo isotope Be. Calculations in the fermionic molecular
dynamics approach show a strong sensitivity of the charge radius to the
structure of Be. The experimental charge radius is consistent with a
breakdown of the N=8 shell closure.Comment: 5 pages, 3 figure
Test of Time Dilation Using Stored Li+ Ions as Clocks at Relativistic Speed
We present the concluding result from an Ives-Stilwell-type time dilation
experiment using 7Li+ ions confined at a velocity of beta = v/c = 0.338 in the
storage ring ESR at Darmstadt. A Lambda-type three-level system within the
hyperfine structure of the 7Li+ triplet S1-P2 line is driven by two laser beams
aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler
shifted frequencies required for resonance are measured with an accuracy of < 4
ppb using optical-optical double resonance spectroscopy. This allows us to
verify the Special Relativity relation between the time dilation factor gamma
and the velocity beta to within 2.3 ppb at this velocity. The result, which is
singled out by a high boost velocity beta, is also interpreted within Lorentz
Invariance violating test theories
Collinear laser spectroscopy of atomic cadmium
Hyperfine structure and factors of the atomic 5s\,5p\,\; ^3\rm{P}_2
\rightarrow 5s\,6s\,\; ^3\rm{S}_1 transition are determined from collinear
laser spectroscopy data of Cd and Cd. Nuclear
magnetic moments and electric quadrupole moments are extracted using reference
dipole moments and calculated electric field gradients, respectively. The
hyperfine structure anomaly for isotopes with and nuclear
ground states and isomeric states is evaluated and a linear
relationship is observed for all nuclear states except . This
corresponds to the Moskowitz-Lombardi rule that was established in the mercury
region of the nuclear chart but in the case of cadmium the slope is
distinctively smaller than for mercury. In total four atomic and ionic levels
were analyzed and all of them exhibit a similar behaviour. The electric field
gradient for the atomic 5s\,5p\,\; ^3\mathrm{P}_2 level is derived from
multi-configuration Dirac-Hartree-Fock calculations in order to evaluate the
spectroscopic nuclear quadrupole moments. The results are consistent with those
obtained in an ionic transition and based on a similar calculation.Comment: 12 pages, 5 figure
Observation of the hyperfine transition in lithium-like Bismuth : Towards a test of QED in strong magnetic fields
We performed a laser spectroscopic determination of the hyperfine
splitting (HFS) of Li-like and repeated the measurement
of the HFS of H-like . Both ion species were
subsequently stored in the Experimental Storage Ring at the GSI
Helmholtzzentrum f\"ur Schwerionenforschung Darmstadt and cooled with an
electron cooler at a velocity of . Pulsed laser excitation of
the hyperfine-transition was performed in anticollinear and collinear
geometry for and , respectively, and
observed by fluorescence detection. We obtain for , different from the literature
value, and for .
These values provide experimental evidence that a specific difference between
the two splitting energies can be used to test QED calculations in the
strongest static magnetic fields available in the laboratory independent of
nuclear structure effects. The experimental result is in excellent agreement
with the theoretical prediction and confirms the sum of the Dirac term and the
relativistic interelectronic-interaction correction at a level of 0.5%
confirming the importance of accounting for the Breit interaction.Comment: 5 pages, 2 figure
Precision Test of Many-Body QED in the Be Fine Structure Doublet Using Short-Lived Isotopes
Absolute transition frequencies of the 2s\; ^2{\rm S}_{1/2} \rightarrow
2p\;^2\mathrm{P}_{1/2,3/2} transitions in Be were measured for the
isotopes Be. The fine structure splitting of the state and its
isotope dependence are extracted and compared to results of \textit{ab initio}
calculations using explicitly correlated basis functions, including
relativistic and quantum electrodynamics effects at the order of
and . Accuracy has been improved in both the theory and
experiment by 2 orders of magnitude, and good agreement is observed. This
represents one of the most accurate tests of quantum electrodynamics for
many-electron systems, being insensitive to nuclear uncertainties.Comment: 5 pages, 2 figure
Commissioning of the HITRAP Cooling Trap with Offline Ions
Highly charged heavy ions at rest offer a wide spectrum of precision measurements. The GSI Helmholtzzentrum fĂŒr Schwerionenforschung GmbH is able to deliver ions up to U92+. As the production of these heavy, highly charged ions requires high kinetic energies, it is necessary to decelerate these ions for ultimate precision. The broad energy distribution, which results from the deceleration in the HITRAP linear decelerator, needs to be reduced to allow for further transportation and experiments. The HITRAP cooling trap is designed to cool, i.e., reduce, this energy spread by utilizing electron cooling. The commissioning of this trap is done with Ar16+-ions from a local EBIT ion source. By analyzing the signal of stored ions after ejection, properties such as ion lifetime, charge exchange, and ion motions can be observed. Here, we provide an overview of the recent results of the commissioning process and discuss future experiments
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