News Archive 2013
Chiral molecules are molecules that have a non-superposable mirror image. Original and mirror image of chiral molecules are different in the same way as our right and left hand. Most organic molecules have such handedness, also called chirality or enantiomorphy. The different configurations of a chiral molecule mostly also have different biological and pharmaceutical properties. It is therefore very important to investigate and reveal the spatial structure of such organic molecules.
Members of the "atomic and molecular quantum dynamics" group around Andreas Wolf and the "ASTROLAB group" of Holger Kreckel together with chemists of the Ruprecht-Karls-Universität Heidelberg have succeeded in imaging the spatial atomic configuration of chiral molecules applying a novel method. This allowed for the determination of the so-called absolute configuration which also yields the sense of chirality of the molecules, which states whether a sample contains right- or left handed molecules. The newly developed method combines mass spectrometry with subsequent Coulomb explosion imaging. It has been applied on the chiral epoxide dideuterooxirane in the gas phase. The new method is very promising for future applications with chiral molecules.
Further information can be found in the recently published "Science" article of P. Herwig et al. and the detailed press release of the MPIK .
Further press releases:
The possibility of sudden structural changes in unexplored regions of the nuclear chart challenges our theoretical understanding of the atomic nucleus. In the neutron-rich A≈100 region, sudden changes in the mass surface make extrapolations hazardous and alter the predicted natural abundance of the elements. The neutron-rich A≈100 region has thus been extensively studied using theoretical approaches such as the interacting boson model (IBM) and Hartree-Fock-Bogoliubov (HFB).
In a recently in Physical Review C published article V. Manea et al. report the determination of the masses of the neutron-rich 98–100Rb isotopes with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE /CERN , Geneva. The mass of 100Rb was determined for the first time. 100Rb is the shortest-lived nuclide measured using ISOLTRAP. The mass of 99Rb could be significantly improved. Due to the low yield and short half-life of 100Rb and 99Rb, the Ramsey-type TOF-ICR method was used. The possible 98Rb isomeric state was not observed during conventional TOF-ICR measurements.
The measured masses confirm that the rubidium isotopes follow the trend of the isotopic chains with higher proton numbers and suggest that the sudden shape transition at N=60 extends at least as far as Z=37. This marks the known low-Z frontier of the shape transition at N=60 since for Z=36 no such shape transition takes place for 96Kr.
The systematics of two-neutron separation energies and charge radii in the measured region have been compared
with the results of Hartree-Fock-Bogoliubov (HFB) calculations. This allowed to describe the evolution of nuclear
shapes towards the krypton isotopic chain and to discuss the changes between the rubidium and krypton isotopic
chains. It could be shown that the pairing interaction has a significant impact on the predicted position of the
shape transition, as well as the absolute values of the two-neutron separation energies and charge radii of the
deformed nuclei. A transition to large prolate deformation or, alternatively, the predominance of oblate deformation
is proposed as explanation for the different behavior of the krypton isotopes.
The analysis was extended to the N∼56 region to investigate the role of dynamic octupole correlations (octupole collectivity) in explaining the global picture of the mass surface around A=100.
Please read more in the article ... >
The first Chinese-German Symposium about "High Precision Experiments with Stored Exotic and Stable Ions" takes place from November 6 to 11, 2013, in Lanzhou, China. Experts from Germany, China and three other countries meet to discuss current topics of storage ring physics.
The symposium has been initiated by a proposal submitted by Dr. Yuri Litvinov , GSI , and Prof. Yuhu Zhang , Institute of Modern Physics in Lanzhou . After the evaluation of the proposal by referees from Germany and China, the symposium has been approved in September 2013. For the realization of the events as well as travel funds for 18 participants a grant amounting to 173 600 RMB (approx. 20 000 Euro) is provided by the Sino-German Centre for the Advancement of Science (CDZ). The CDZ is a research funding institution funded as joint venture by the German Research Foundation (DFG) and the National Natural Science Foundation of China (NSFC) being resident in Beijing. Main goal of the CDZ is the promotion of the scientific cooperation between China and Germany in the fields of natural, life, managment and engineering sciences.
Please read more on the webpage of the symposium ... >
The 16th International Conference on the Physics of Highly Charged Ions (HCI 2012 ) was held at the Ruprecht-Karls University in Heidelberg, Germany, 2–7 September 2012. It was co-organized by the Max Planck Institute for Nuclear Physics (MPIK).
The physics of highly charged ions (HCI) is a rapidly developing and attractive field of research with impact upon many other research disciplines. The Heidelberg HCI 2012 conference brought together senior experts with students, young researchers and scientists from related disciplines who make use and give back impact upon the research with HCI.
The Conference Proceedings of HCI 2012 have recently been published in Physica Scripta. Our division contributes six articles on precision spectroscopy of resp. experimental developments for HCI. Please read more in the preface and the articles of the proceedings.
Klaus Blaum together with Holger Müller (Berkeley) and Nathal Severijns (KU Leuven) are Guest Editors of a two-volume Special Issue on "Precision Experiments and Fundamental Physics at Low Energies" of "Annalen der Physik" (please see news of 23.07.13). Part II of the Special Issue has just been published.
In the second volume reviews and results from dedicated efforts to study fundamental constants, to test basic symmetries of the Standard Model and search for new physics, are reported.
High-precision measurements of fundamental constants, e.g. the fine structure constant alpha, are important since their accurate values are used in a wide range of applications, they help testing the accepted laws of physics, and can be used to define the international system of units (SI). In a future version of the SI, the Planck constant h will have a defined value.
There is strong observational evidence that the Standard Model of particle physics is incomplete. It is e.g. unable to explain why the universe is dominated by matter when the theory exhibits perfect matter-antimatter (CPT-)symmetry, as any Lorentz-invariant, local field theory must. Different experimental high-precision tests of fundamental symmetries, such as Lorentz and CPT symmetry, may reveal minuscule deviations from exact symmetry. Such experimental results will lead to new physics as they provide strong criteria for (supersymmetric) theories beyond the Standard Model.
Please read more in the editorial and the articles of part II of the Special Issue.
Klaus Blaum together with Yuri Litvinov (GSI Darmstadt) are Editors of a Special Issue on "100 years of Mass Spectrometry" of the "International Journal of Mass Spectrometry" which has just been published.
Today, in the year 2013, we can look back on 100 years of mass spectrometry. Its success story began in 1913 when J.J. Thomson reported on experiments with "Rays of positive electricity" (today: "ion beams"). With his "parabola spectrograph" Thomson also discovered the existence of neon isotopes, or more generally speaking, new nuclides. Soon after, his student F.W. Aston found the so-called "mass defect" of atomic nuclei.
The pioneering experiments by J.J. Thomson and F.W. Aston and in parallel by A.J. Dempster boosted the interest to atomic mass measurements. Ever since the first experiments and up to the present days, new results on atomic masses inspire the development of nuclear theories. The great success of the meanwhile century-long mass measurement endeavor and thereupon-based discoveries is reflected by a number of Nobelprizes, beginning from F.W. Aston (NP, 1922).
The recently published Special Issue aims at reviewing the successful story of mass measurements over the last hundred years. A special emphasize was given to examples in atomic and nuclear physics research. Please read more in the preface and the articles of the Special Issue.
High-precision measurements allow physicists to probe nature's fundamental interactions which e.g. contribute to finding and verifying a theory beyond the Standard Model of particle physics that might unify gravity and quantum mechanics into a theory of quantum gravity.
Klaus Blaum together with Holger Müller (Berkeley) and Nathal Severijns (KU Leuven) are Guest Editors of a Special Issue on "Precision Experiments and Fundamental Physics at Low Energies" of "Annalen der Physik". The Special Issue consists of two volumes, part I has recently been published, part II will be published this August. In both volumes current precision efforts investigating fundamental interactions and their properties at lowest energies are addressed in review articles and in a series of original papers which focus mainly on fundamental constants and symmetry tests.
Accurate atomic masses from Penning trap measurements, e.g. with the TITAN Penning trap mass
spectrometer, yield precise information to test the postulated unitarity of the
Cabibbo-Kobayashi-Maskawa quark-mixing matrix. Further improved measurement precision as well as
important theoretical progress might lead to new physics beyond the Standard Model.
Among other methods, Penning trap experiments also contribute to the investigation of fundamental constants, e.g. the fine structure constant α, and to symmetry tests, e.g. the test of the fundamental Charge, Parity, and Time Reversal (CPT) symmetry. In recent years experiments with antimatter at the Antiproton Decelerator facility at CERN have provided important results which allow for different new tests of the CPT symmetry through comparisons of properties of particles and corresponding antiparticles.
Please read more in the editorial and the articles of the Special Issue.
The description of exotic nuclei with extreme neutron-to-proton asymmetries poses enormous challenges, because most theoretical models have been developed for nuclei at the valley of stability. Exceedingly neutron-rich nuclei become sensitive to new aspects of nuclear forces. Based on the chiral effective field theory calculations with three-nucleon forces lead to theoretical predictions of the nuclear interactions far from stability. These predictions have recently been validated by direct Penning-trap mass measurements of 51Ca and 52Ca at TITAN/TRIUMF , Canada. The results established a substantial change from the previous mass evaluation and leave completely open how nuclear masses evolve past 52Ca. Thus mass measurements on heavier calcium isotopes are crucial to increase our understanding of neutron-rich matter.
F. Wienholtz et al. present the results of the first mass measurements of the exotic
calcium isotopes 53Ca and 54Ca which have just been published in the prestigious scientific
journal "Nature". The measurements were performed using the high-resolution multi-reflection
time-of-flight mass spectrometer/separator (MR-TOF MS) ISOLTRAP at
CERN , Geneva. It is the first application
of the MR-TOF MS method for rare isotope beams.
At first, the MR-TOF MS was operated as an isobar separator to measure the masses of 51Ca and 52Ca by determining the cyclotron-frequency ratios. The values agree well with the mentioned recent measurements by TITAN and the uncertainty could be reduced by a factor of 40 and 80 for 51Ca resp. 52Ca. Because of the low production rates and copious isobaric contamination such Penning-trap measurements were not possible for 53Ca+ and 54Ca+. Thus for 53Ca+ and 54Ca+ the MR-TOF device itself was employed as a mass spectrometer which enabled the physicists to experimentally determine the masses of 53,54Ca for the first time. The values of the two-neutron separation energy S2n are a preferred probe of the evolution of nuclear structure with neutron number. The S2n values can be deduced from the determined mass excess. The new 53Ca and 54Ca ISOLTRAP masses revealed a pronounced decrease in S2n which is in excellent agreement with the theoretical predictions. Therefore, the new data unambiguously establish a prominent shell closure at N=32 and show that shell effects do not smear out far from stability.
The first mass measurements of the 53Ca and 54Ca isotopes present anchor points to pin down nuclear forces that are explored by the chiral effective field theory.
Please read more in the "Nature" article ... >
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The fundamental Charge, Parity, and Time Reversal (CPT) symmetry is one of the most fundamental symmetries in the Standard Model of particle physics. It implies the exact equality between the properties of particles and their corresponding antiparticles. Any measured difference between the properties of an exactly conjugated matter/antimatter system would potentially contribute to the solution of the observed matter/antimatter asymmetry in the universe. This inspires physicists to invent novel techniques and experimental setups for the high-precision comparison of the properties of matter and antimatter at lowest energies and with highest precision.
In a just in Physics Letters B published article A. Mooser et al. report on the first
successful demonstration of the double Penning Trap technique with a single proton.
This novel experimental method aims for the high-precision comparison of the magnetic
moments of the proton and the antiproton. The general method to determine the magnetic
moment of a single particle stored in a cryogenic Penning trap is to measure the spin
precession frequency (Larmor frequency) non-destructively by means of the continuous
Stern-Gerlach effect. Therefore a very large magnetic field inhomogeneity (magnetic
bottle) is superimposed to the trap, which couples the spin-magnetic moment of the
stored particle to its axial oscillation frequency. However, this magnetic bottle
broadens the Larmor resonance line significantly, and thus, limits the experimental
precision. The elegant double Penning trap method overcomes this problem by using
two separate Penning traps, the precision trap and the analysis trap. The spin-state
detection is carried out in the analysis trap with the superimposed strong magnetic
bottle. The measurement of the cyclotron frequency and the excitation of spin-flips
at the Larmor frequency are performed in the precision trap with a 75 000-fold more
homogeneous magnetic field. This reduces the line width of the spin resonance
drastically and potentially improves the precision by more than three orders of
The reported first successful application of the double Penning Trap technique to a single proton paves the way towards the first direct high-precision measurement of the particle’s magnetic moment. The application of this method to a single trapped antiproton, which is planned at the BASE experiment at the antiproton decelerator of CERN, will provide one of the most stringent tests of the CPT symmetry.
Please read more in the article ... >
Further information about the recently approved BASE experiment at the antiproton decelerator of CERN can be found in the CERN bulletin .
The nuclear shell model was introduced to explain the observed shell structure in nuclei. A very stringent test of this model can be performed by the determination of the electric quadrupole moment as it exhibits a linear behavior with changing valence neutron number according to the model. The main difficulty is to predict which nuclei are likely to display this linear signature. The isotopes of cadmium in the neighborhood of the "magic" tin proved to be the most revealing case so far and provide important information for the prediction of complex nuclei as well as the understanding of stellar nucleosynthesis.
In a just in Physical Review Letters published article D. T. Yordanov et al. report on the investigation of neutron-rich isotopes of cadmium up to the N = 82 shell closure by high-resolution laser spectroscopy. The measurements were carried out with the collinear laser spectroscopy setup COLLAPS at ISOLDE-CERN , Geneva. The application of deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity to access the very exotic odd-mass isotopes of cadmium. This led to the discovery of the two long-lived 11/2- isomers 127Cd and 129Cd. A very remarkable experimental result is that all quadrupole moments of the nuclear state with a total spin-orbit value of 11/2, the unique-parity h11/2 intruder orbital, show a linear behavior with changing neutron number. This confirms the applicability of the nuclear shell model even for complex nuclei.
Please read more in the article ... >
Detailed information in the press releases of the MPIK and the idw .
The article has been selected for a Viewpoint in Physics. Please read also the viewpoint on the article by John Wood (Georgia Institute of Technology).
The nuclear shell model forms the basis for our understanding of atomic nuclei. Since more and more rare-isotope beams are available, new regions of the nuclear chart can be explored. Thus, strong modifications to the well-known shell structure are required and the theoretical shell-model effective interactions have to be improved. In the interplay between theory and experiment spins and magnetic moments of ground states play a crucial role.
In a just in Physical Review Letters published article J. Papuga et al. are presenting the measured ground-state spins and magnetic moments of 49K with two and 51K with four neutrons beyond the magic neutron number N = 28. They have been measured using bunched-beam high-resolution collinear laser spectroscopy at ISOLDE/CERN in Geneva. From the hyperfine spectrum of 49K a ground-state spin of I = 1/2 has been determined. The observed hyperfine structure of 51K requires a spin I > 1/2 and a spin I = 5/2 or higher could be excluded at a confidence level of 95%. Thus, I = 3/2 for 51K is highly probable. The obtained magnetic moments μ(49K) = + 1.3386(8)μN and μ(51K) = + 0.5129(22)μN reveal a mixed configuration for 49K and a rather pure π1d-13/2 configuration for 51K.
Please read more in the article ... >
The currently most precise values for the proton and antiproton magnetic moments come from measurements of the hyperfine splitting in atomic hydrogen resp. super-hyperfine spectroscopy of antiprotonic helium. Advanced Penning trap systems have now opened the way for direct precision measurements of the proton and antiproton magnetic moments with no need for theoretical bound-state corrections. The direct high-precision comparison of the magentic moments of the proton and the antiproton provides a very stringent test of charge, parity, time (CPT) symmetry in the baryon sector.
In a just in Physical Review Letters published article A. Mooser et al. report on the first detection
of single spin-flips of a single proton. Spin-flips can be induced by a drive radio frequency and
observed non-destructively by means of the continuous Stern-Gerlach effect.
Therefore a very large magnetic field inhomogeneity (magnetic bottle) is needed, which limits the precision
of the statistical detection of the spin-flips. In order to improve the precision by several orders of
magnitude, a cryogenic double-Penning trap has been used in the experiment. This has the advantage that the measurement
of the cyclotron frequency and the excitation of spin-flips at the Larmor frequency happen in a first
Penning trap (precision trap) with a homogeneous magnetic field. The spin-state detection is carried
out in a second Penning trap (analysis trap) with a magnetic bottle, which couples the spin magnetic
moment of the single proton to its axial motion. Jumps in the oscillation frequency
indicate spin-flips and were identified using a Bayesian analysis. The Bayes
method clearly is superior to the threshold method. It nicely confirms the spin-flips visible
in the raw data and provides a consistent picture of the time-evolution of the proton spin-state
The used double-Penning trap technique requires that single spin-flips can be resolved, which so far was not possible with nuclear spins. The successful first observation of single spin-flips of a single proton now enables the application of the double Penning-trap method to measure magnetic moments of both the proton and the antiproton with at least 10-9 precision. As already mentioned, this allows for a high-precision test of the matter-antimatter symmetry.
Please read more in the article ... >
Type I X-ray bursts are thermonuclear explosions on the surface of neutron stars, which accrete matter from the companion star. Typical bursts have rise times of a few seconds and can last from 10s to minutes with recurrence times of hours to days. Understanding the observed light curves and the composition of the crust, which consists of the ashes of past bursts, requires an understanding of the complex nuclear processes producing energy during X-ray bursts, among others the rp-process (rapid proton capture process). The rp-process is a sequence of proton captures and β+ decays near the proton drip line. An important parameter for the understanding of the rp-process path is the proton separation energy (Sp), which can be deduced from the mass excess. Nuclear masses therefore largely determine the rp-process path and must be known with an accuracy at least of the order of kT ≈ 50-100 keV.
In a just in Astrophysical Journal Letters published article X. L. Yan et al. report on the results from
new mass measurements of nuclei along the rp-process path between Ti and Ni.
The measurements have been performed at the Cooler-Storage Ring at the Heavy Ion Research Facility in Lanzhou
(HIRFL-CSR , pictures ),
China, employing the isochronous mass spectrometry technique. The masses of a series of isospin
projection Tz = -3/2 nuclides, 41Ti, 43V, 45Cr, 47Mn, 49Fe, 53Ni, and 55Cu have been determined with a
relative uncertainty of ∼10-6–10-7.
The new accurate mass values are important for modeling of the rp-process in X-ray bursts. Most notably it could be shown that the new mass of 45Cr is of importance for the rp-process path because of its impact on the proton separation energy of 45Cr and the 45Cr(γ,p) photodisintegration rate. The mass excess value for 45Cr was determined to be ME(45Cr) = -19515(35) keV, which leeds to the proton separation energy Sp(45Cr) = 2.69±0.13 MeV. This excludes a possible formation of a strong Ca–Sc cycle in X-ray bursts.
Please read more in the article ... >
The cyclotron frequency of an ion in the magnetic field of a Penning trap currently offers the most precise access to the nuclear masses of short-lived isotopes. Physicists of the Max Planck Institute for Nuclear Physics Heidelberg and the University Greifswald have now at the GSI Helmholtzzentrum Darmstadt succeeded in imaging the cyclotron motion itself, which enhances the accuracy of the measurements comparable with the second hand of a clock. This significantly reduces the necessary measurement time for short-lived nuclides.
Please read more in the just in Physical Review Letters online published article of S. Eliseev et al. ... >
Detailed press releases about the article:
On occasion of the Nobel Symposium "Physics with Radioactive Beams, 2012" a special volume has just been published in Physica Scripta . Klaus Blaum et al. contribute to this special volume with a review article on "Precision atomic physics techniques for nuclear physics with radioactive beams". In the review article the basic principles of laser spectroscopic investigations, Penning-trap and storage-ring mass measurements of short-lived nuclei are summarized and selected physics results are discussed.
Nuclear physics with radioactive beams opens up new venues to investigate nature on a deeper level then ever possible before. Significant progress has been achieved in Penning-trap and storage-ring mass spectrometry as well as laser spectroscopy of radioactive nuclei within the last decade. Today, the determination of ground state properties from mass spectrometry and laser spectroscopy is possible with unrivaled precision and sensitivity. These improved techniques provide accurate masses, binding energies, Q-values, charge radii, spins and electromagnetic moments. The highly accurate numbers give insight into details of the nuclear structure for a better understanding of the underlying effective interactions, provide important input for studies of fundamental symmetries in physics, and help to understand the nucleosynthesis processes that are responsible for the observed chemical abundances in the Universe.
All mentioned experimental and theoretical fields of nuclear physics benefited enormously from the progress in adopting atomic physics techniques to the specific requirements posed by radioactive isotopes. Thus, the improved and novel techniques of Penning-trap and storage-ring mass spectrometry as well as laser spectroscopy have become key tools in detailed studies of physics with radioactive beams. Basically all current facilities and planned facilities include these modern techniques in their programs.
Please read more in the article ... >
The nucleosynthesis process of rapid neutron capture (r process) has been suggested to explain the abundance of lighter elements close to stability and heavier, neutron-rich nuclides that accumulate near shell closures as observed in our Solar System and Galaxy. Supernovae have been favored for a long time to be the astrophysical site where this r process takes place. It has been discussed, that neutron stars could be an alternative r process site because of their large neutron content. The r process could occur during the decompression of crustal matter ejected into the interstellar medium. The astrophysical plausibility of this scenario most importantly requires a proper understanding of the composition of the outer crusts of neutron stars. The modeling of the composition of neutron-star crusts depends strongly on the knowledge of binding energies of neutron-rich nuclides near the N=50 and N=82 shell closures. Thus, high-precision mass measurements are indispensable.
In a just in Physical Review Letters published article R. N. Wolf et al. report on the first precise measurement of the mass of the exotic nuclide 82Zn. The mass measurement was performed with the ISOLTRAP setup at the ISOLDE-CERN facility using a recent development of time-of-flight mass spectrometry for on-line purification of radioactive ion beams to access more exotic species. This measurement represents the frontier of knowledge for the N=50 shell and as such the limit of knowledge for fathoming the neutron-star crust composition. Based on the new experimental 82Zn mass value, calculations of the neutron-star crust composition were performed. The obtained composition profile is not only altered but now constrained by experimental data deeper into the crust than before.
Figure 1 of this PRL article, the depth profile of a neutron star with the changed composition profil of the crust, has been selected for the front cover of the PRL issue of 25 January 2013.
Please read more in the article ... >
Please also read the Synopsis and the following press releases:
- Informationsdienst Wissenschaft
- DPG (Pro-Physik)
- Science News
- ISOLDE News (31.01.2013)
The g factor of an electron (the strength of the magnetic interaction of the electron spin) can be predicted very exactly by QED and also can be experimental measured with comparable accuracy. The comparison of those two values represents to date the most accurate test of bound-state QED (BS-QED) in strong electromagnetic fields.
In a just in Physical Review Letters published article A. Wagner et al. report on the high-precision g factor measurement of lithiumlike silicon 28Si11+ and the comparison with the improved theoretical value. The g factor has been measured in a triple-Penning trap with a relative uncertainty of 1.1·10-9 to be gexp = 2.000 889 889 9(21). The theoretical prediction for this value was calculated to be gth = 2.000 889 909(51) improving the accuracy to 2.5·10-8 due to the first rigorous evaluation of the two-photon exchange correction. Thus, the measured value is in excellent agreement with the theoretical prediction and yields the most stringent test of bound-state QED for the g factor of the 1s22s state and the relativistic many-electron calculations in a magnetic field. It represents the most precise g factor determination of a three-electron system to date.
Please read more in the article ... >
Please also read the press releases of the Max Planck Institute for Nuclear Physics and the DPG (Pro-Physik)