145 research outputs found
Nuclear Masses in Astrophysics
Among all nuclear ground-state properties, atomic masses are highly specific
for each particular combination of N and Z and the data obtained apply to a
variety of physics topics. One of the most crucial questions to be addressed in
mass spectrometry of unstable radionuclides is the one of understanding the
processes of element formation in the Universe. To this end, accurate atomic
mass values of a large number of exotic nuclei participating in nucleosynthesis
are among the key input data in large-scale reaction network calculations. In
this paper, a review on the latest achievements in mass spectrometry for
nuclear astrophysics is given.Comment: Proceedings of the 10th Symposium on Nuclei in the Cosmos, NIC X -
Mackinac Island, Michigan, USA (10 pages, 4 figures
First-order perturbative calculation of the frequency-shifts caused by static cylindrically-symmetric electric and magnetic imperfections of a Penning trap
The ideal Penning trap consists of a uniform magnetic field and an
electrostatic quadrupole potential. Cylindrically-symmetric deviations thereof
are parametrized by the coefficients Bn and Cn, respectively. Relativistic
mass-increase aside, the three characteristic eigenfrequencies of a charged
particle stored in an ideal Penning trap are independent of the three motional
amplitudes. This three-fold harmonicity is a highly-coveted virtue for
precision experiments that rely on the measurement of at least one
eigenfrequency in order to determine fundamental properties of the stored
particle, such as its mass. However, higher-order contributions to the ideal
fields result in amplitude-dependent frequency-shifts. In turn, these
frequency-shifts need to be understood for estimating systematic experimental
errors, and eventually for correcting them by means of calibrating the
imperfections. The problem of calculating the frequency-shifts caused by small
imperfections of a near-ideal trap yields nicely to perturbation theory,
producing analytic formulas that are easy to evaluate for the relevant
parameters of an experiment. In particular, the frequency-shifts can be
understood on physical rather than purely mathematical grounds by considering
which terms actually drive them. Based on identifying these terms, we derive
general formulas for the first-order frequency-shifts caused by any
perturbation parameter Bn or Cn.Comment: 18 pages, 1 figure, 0 tables. Accepted manuscript subsequently
published. Streamlined the introduction. Optimized choice of summation
variable
Classical calculation of relativistic frequency-shifts in an ideal Penning trap
The ideal Penning trap consists of a uniform magnetic field and an
electrostatic quadrupole potential. In the classical low-energy limit, the
three characteristic eigenfrequencies of a charged particle trapped in this
configuration do not depend on the amplitudes of the three eigenmotions. No
matter how accurate the experimental realization of the ideal Penning trap, its
harmonicity is ultimately compromised by special relativity. Using a classical
formalism of first-order perturbation theory, we calculate the relativistic
frequency-shifts associated with the motional degrees of freedom for a spinless
particle stored in an ideal Penning trap, and we compare the results with the
simple but surprisingly accurate model of relativistic mass-increase.Comment: 8 pages, 0 figures, 1 table; Accepted manuscript subsequently
published with a slightly extended description of the perturbative metho
g factor of lithiumlike silicon 28Si11+
The g factor of lithiumlike 28Si11+ has been measured in a triple-Penning
trap with a relative uncertainty of 1.1x10^{-9} to be g_exp=2.0008898899(21).
The theoretical prediction for this value was calculated to be
g_th=2.000889909(51) improving the accuracy to 2.5x10^{-8} due to the first
rigorous evaluation of the two-photon exchange correction. The measured value
is in excellent agreement with the state-of-the-art theoretical prediction and
yields the most stringent test of bound-state QED for the g factor of the
1s^22s state and the relativistic many-electron calculations in a magnetic
field
A reservoir trap for antiprotons
We have developed techniques to extract arbitrary fractions of antiprotons
from an accumulated reservoir, and to inject them into a Penning-trap system
for high-precision measurements. In our trap-system antiproton storage times >
1.08 years are estimated. The device is fail-safe against power-cuts of up to
10 hours. This makes our planned comparisons of the fundamental properties of
protons and antiprotons independent from accelerator cycles, and will enable us
to perform experiments during long accelerator shutdown periods when background
magnetic noise is low. The demonstrated scheme has the potential to be applied
in many other precision Penning trap experiments dealing with exotic particles.Comment: Article by the BASE-collaboration at CERN. Results from the
Antiproton physics run 2014. Submitted to International Journal of Mass
Spectrometry, 8th of April 201
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
Long-term monitoring of the internal energy distribution of isolated cluster systems
A method is presented to monitor the internal energy distribution of cluster
anions via delayed electron detachment by pulsed photoexcitation and
demonstrated on Co in an electrostatic ion beam trap. In cryogenic
operation, we calibrate the detachment delay to internal energy. By laser
frequency scans, at room temperature, we reconstruct the time-dependent
internal energy distribution of the clusters. The mean energies of ensembles
from a cold and a hot ion source both approach thermal equilibrium. Our data
yield a radiative emission law and the absorptivity of the cluster for thermal
radiation.Comment: Manuscript LaTeX with 6 pages, 4 figures, plus LaTeX supplement with
9 pages, 4 figures and 2 tables. This article has been accepted by Physical
Review Letter
High-precision measurement of the atomic mass of the electron
The quest for the value of the electron's atomic mass has been subject of
continuing efforts over the last decades. Among the seemingly fundamental
constants which parameterize the Standard Model (SM) of physics and which are
thus responsible for its predictive power, the electron mass me plays a
prominent role, as it is responsible for the structure and properties of atoms
and molecules. This manifests in the close link with other fundamental
constants, such as the Rydberg constant and the fine-structure constant
{\alpha}. However, the low mass of the electron considerably complicates its
precise determination. In this work we present a substantial improvement by
combining a very accurate measurement of the magnetic moment of a single
electron bound to a carbon nucleus with a state-of-the-art calculation in the
framework of bound-state Quantum Electrodynamics. The achieved precision of the
atomic mass of the electron surpasses the current CODATA value by a factor of
13. Accordingly, the result presented in this letter lays the foundation for
future fundamental physics experiments and precision tests of the SM
Literatur-Rundschau
Margreth LĂŒnenborg: Joumalismus als kultureller Prozess (Klaus Arnold)Institut zur Förderung publizistischen Nachwuchses/Deutscher Presserat (Hg.): Ethik im Redaktionsalltag (Horst Pöttker)Elisabeth Hurth: "Gute Nacht, John Boy!". Familien vor und auf dem Bildschirm (Eckhard Bieger)GĂŒnther Mees: Stimme der Stimmlosen. UCIP - Katholische Weltunion der Presse (Ferdinand Oertel)Harald Schleicher/Alexander Urban (Hg.): Filme machen (Michael Harnischmacher)Heike B. Görtemaker: Ein deutsches Leben. Die Geschichte der Margret Boveri 1900-1975 (Verena Blaum)
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
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