84 research outputs found
Hyperfine-induced effects on the linear polarization of the K emission from helium-like ions
The linear polarization of the characteristic photon emission from
few-electron ions is studied for its sensitivity with regard to the nuclear
spin and magnetic moment of the ions. Special attention is paid, in particular,
to the K (1s 2p_{3/2} ^{1,3}P_{1,2} \to 1s^2 ^1S_0) decay of
selected helium-like ions following the radiative electron capture into
initially hydrogen-like species. Based on the density matrix theory, a unified
description is developed that includes both, the many-electron and hyperfine
interactions as well as the multipole-mixing effects arising from the expansion
of the radiation field. It is shown that the polarization of the K
line can be significantly affected by the mutipole mixing between the leading
and hyperfine-induced components of 1s2p ^3P_2, F_i \to 1s^2 ^1S_0,
F_f transitions. This - mixing strongly depends on the nuclear
properties of the considered isotopes and can be addressed experimentally at
existing heavy-ion storage rings
Dominant Secondary Nuclear Photoexcitation with the X-ray Free Electron Laser
The new regime of resonant nuclear photoexcitation rendered possible by x-ray
free electron laser beams interacting with solid state targets is investigated
theoretically. Our results unexpectedly show that secondary processes coupling
nuclei to the atomic shell in the created cold high-density plasma can dominate
direct photoexcitation. As an example we discuss the case of Mo isomer
depletion for which nuclear excitation by electron capture as secondary process
is shown to be orders of magnitude more efficient than the direct laser-nucleus
interaction. General arguments revisiting the role of the x-ray free electron
laser in nuclear experiments involving solid-state targets are further deduced.Comment: 6 pages, 2 figures; v2 updated to published version; results
unchange
Can Hyperfine Excitation explain the Observed Oscillation-Puzzle of Nuclear Orbital Electron Capture of Hydrogen-like Ions?
Modulated in time orbital electron capture (EC) decays have been observed
recently in stored H-like Pr and Pm ions.
Although, the experimental results are extensively discussed in literature, a
firm interpretation has still to be established. Periodic transitions between
the hyperfine states could possible lead to the observed effect. Both selected
nuclides decay to stable daughter nuclei via allowed Gamow-Teller transitions.
Due to the conservation of total angular momentum, the allowed EC decay can
only proceed from the hyperfine ground state of parent ions. In this work we
argue that periodic transitions to the excited hyperfine state (sterile) in
respect to the allowed EC decay ground state cannot explain the observed decay
pattern
Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics
Neutron capture cross sections of unstable isotopes are important for
neutron-induced nucleosynthesis as well as for technological applications. A
combination of a radioactive beam facility, an ion storage ring and a high flux
reactor would allow a direct measurement of neutron induced reactions over a
wide energy range on isotopes with half lives down to minutes. The idea is to
measure neutron-induced reactions on radioactive ions in inverse kinematics.
This means, the radioactive ions will pass through a neutron target. In order
to efficiently use the rare nuclides as well as to enhance the luminosity, the
exotic nuclides can be stored in an ion storage ring. The neutron target can be
the core of a research reactor, where one of the central fuel elements is
replaced by the evacuated beam pipe of the storage ring. Using particle
detectors and Schottky spectroscopy, most of the important neutron-induced
reactions, such as (n,), (n,p), (n,), (n,2n), or (n,f), could
be investigated.Comment: 5 pages, 7 figures, Invited Talk given at the Fifteenth International
Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15),
Dresden, Germany, 201
SPARC Collaboration: New Strategy for Storage Ring Physics at FAIR
SPARC collaboration at FAIR pursues the worldwide unique research program by
utilizing storage ring and trapping facilities for highly-charged heavy ions.
The main focus is laid on the exploration of the physics at strong, ultra-short
electromagnetic fields including the fundamental interactions between electrons
and heavy nuclei as well as on the experiments at the border between nuclear
and atomic physics. Very recently SPARC worked out a realization scheme for
experiments with highly-charged heavy-ions at relativistic energies in the
High-Energy Storage Ring HESR and at very low-energies at the CRYRING coupled
to the present ESR. Both facilities provide unprecedented physics opportunities
already at the very early stage of FAIR operation. The installation of CRYRING,
dedicated Low-energy Storage Ring (LSR) for FLAIR, may even enable a much
earlier realisation of the physics program of FLAIR with slow anti-protons.Comment: IX International Workshop on "APPLICATION OF LASERS AND STORAGE
DEVICES IN ATOMIC NUCLEI RESEARCH", Recent Achievements and Future Prospects,
May 13 - 16, 2013, Pozna\'n, Polan
A data analysis method for isochronous mass spectrometry using two time-of-flight detectors at CSRe
The concept of isochronous mass spectrometry (IMS) applying two
time-of-flight (TOF) detectors originated many years ago at GSI. However, the
corresponding method for data analysis has never been discussed in detail.
Recently, two TOF detectors have been installed at CSRe and the new working
mode of the ring is under test. In this paper, a data analysis method for this
mode is introduced and tested with a series of simulations. The results show
that the new IMS method can significantly improve mass resolving power via the
additional velocity information of stored ions. This improvement is especially
important for nuclides with Lorentz factor -value far away from the
transition point of the storage ring CSRe.Comment: published in Chinese Physics C Vol. 39, No. 10 (2015) 10620
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
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