Dennis Renisch

Bio: Dennis Renisch is an academic researcher from University of Mainz. The author has contributed to research in topics: Ion & Ion trap. The author has an hindex of 5, co-authored 12 publications receiving 69 citations. Previous affiliations of Dennis Renisch include Max Planck Society.

Q value and half-life of double-electron capture in 184Os

Abstract: The observation of neutrinoless double-beta transitionswould reveal physics beyond the Standard Model, asit would establish neutrinos to be Majorana particles,which implies a violation of the lepton number conserva-tion. Experiments searching for these transitions have fo-cused on the detection of neutrinoless double-beta decay(0 ) rather than neutrinoless double-electron capture(0). One reason among others is in general the sig-ni cantly shorter half-life of the 0 process. However,in the case of neutrinoless double-electron capture, thetransition is expected to be resonantly enhanced if theinitial and the nal state of the transition are degeneratein energy [1{3].In this work, we investigate neutrinoless double-electron capture in

The concept of laser-based conversion electron M\"ossbauer spectroscopy for a precise energy determination of $^{229m}$Th

Abstract: $^{229}$Th is the only nucleus currently under investigation for the development of a nuclear optical clock (NOC) of ultra-high accuracy. The insufficient knowledge of the first nuclear excitation energy of $^{229}$Th has so far hindered direct nuclear laser spectroscopy of thorium ions and thus the development of a NOC. Here, a nuclear laser excitation scheme is detailed, which makes use of thorium atoms instead of ions. This concept, besides potentially leading to the first nuclear laser spectroscopy, would determine the isomeric energy to 40 $\mu$eV resolution, corresponding to 10 GHz, which is a $10^4$ times improvement compared to the current best energy constraint. This would determine the nuclear isomeric energy to a sufficient accuracy to allow for nuclear laser spectroscopy of individual thorium ions in a Paul trap and thus the development of a single-ion nuclear optical clock.

An RFQ cooler and buncher for the TRIGA-SPEC experiment

Abstract: A linear Paul trap for cooling of ion beams, the former cooler for emittance elimination radiofrequency quadrupole (RFQ) at MISTRAL/ISOLDE, has been installed and commissioned at the TRIGA-SPEC experiment located at the research reactor TRIGA Mainz. It is connected to a hot-surface-ionization ion source and a subsequent mass separator for ionization and pre-separation of neutron-rich fission products as delivered from the reactor. The capability of accumulating and bunching ion beams has been implemented to provide low-emittance ion pulses of 250 ns width containing up to 106 ions. A technical description of the upgraded RFQ as well as its characterization with stable ions is presented. Its installation allows delivery of low-emittance ion bunches to the two branches of the TRIGA-SPEC experiment, namely TRIGA-TRAP and TRIGA-LASER.

Direct mass measurements of cadmium and palladium isotopes and their double-β transition Q values

Abstract: The Q-value of the double-electron capture in Cd-108 has been determined to be (272.04 +/- 0.55) keV in a direct measurement with the double-Penning trap mass spectrometer TRIGA-TRAP. Based on this result a resonant enhancement of the decay rate of Cd-108 is excluded. We have confirmed the double-beta transition Q-values of Cd-106 and Pd-110 recently measured with the Penning-trap mass spectrometers SHIPTRAP and ISOLTRAP, respectively. Furthermore, the atomic masses of the involved nuclides Cd-106, Cd-108, Cd-110, Pd-106, Pd-108 and Pd-110 have been directly linked to the atomic mass standard.

Catching, trapping and in-situ-identification of thorium ions inside Coulomb crystals of 40 Ca + ions

Abstract: Thorium ions exhibit unique nuclear properties with high relevance for testing symmetries of nature, and Paul traps feature an ideal experimental platform for performing high precision quantum logic spectroscopy. Loading of stable or long-lived isotopes is well-established and relies on ionization from an atomic beam. A different approach allows trapping short-lived isotopes available as alpha-decay daughters, which recoil from a thin sample of the precursor nuclide. A prominent example is the short-lived 229mTh, populated in a decay of long-lived 233U. Here, ions are provided by an external source and are decelerated to be available for trapping. Such setups offer the option to trap various isotopes and charge states of thorium. Investigating this complex procedure, we demonstrate the observation of single 232Th+ ions trapped, embedded into and sympathetically cooled via Coulomb interactions by co-trapped 40Ca+ ions. Furthermore, we discuss different options for a non-destructive identification of the sympathetically cooled thorium ions in the trap, and describe in detail our chosen experimental method, identifying mass and charge of thorium ions from the positions of calcium ions, as their fluorescence is imaged on a CCD camera. These findings are verified by means of a time-of-flight signal when extracting ions of different mass-to-charge ratio from the Paul trap and steering them into a detector.

Advances in Atomic, Molecular, and Optical Physics

Abstract: This book contains information on atomic, molecular and optical physics. Topics covered include: muon-catalyzed fusion and cooperative effects in atomic physics.

Nuclear instruments and methods in physics research section B : beam interactions with materials and atoms

Abstract: The impact-induced deposition of Al13 clusters with icosahedral structure on Ni(0 0 1) surface was studied by molecular dynamics (MD) simulation using Finnis–Sinclair potentials. The incident kinetic energy (Ein) ranged from 0.01 to 30 eV per atom. The structural and dynamical properties of Al clusters on Ni surfaces were found to be strongly dependent on the impact energy. At much lower energy, the Al cluster deposited on the surface as a bulk molecule. However, the original icosahedral structure was transformed to the fcc-like one due to the interaction and the structure mismatch between the Al cluster and Ni surface. With increasing the impinging energy, the cluster was deformed severely when it contacted the substrate, and then broken up due to dense collision cascade. The cluster atoms spread on the surface at last. When the impact energy was higher than 11 eV, the defects, such as Al substitutions and Ni ejections, were observed. The simulation indicated that there exists an optimum energy range, which is suitable for Al epitaxial growth in layer by layer. In addition, at higher impinging energy, the atomic exchange between Al and Ni atoms will be favourable to surface alloying.

Mean field and beyond description of nuclear structure with the Gogny force: A review

Abstract: Nowadays, the Gogny force is a referent in the theoretical description of nuclear structure phenomena. Its phenomenological character manifests in a simple analytical form that allows for implementations of techniques both at the mean field and beyond all over the nuclide chart. Over the years, multiple applications of the standard many-body techniques in an assorted set of nuclear structure applications have produced results which are in a rather good agreement with experimental data. The agreement allows for a simple interpretation of those intriguing phenomena in simple terms and gives confidence on the predictability of the interaction. The present status on the implementation of different many body techniques with the Gogny force is reviewed with a special emphasis on symmetry restoration and large amplitude collective motion.

Nuclear matrix elements for neutrinoless double-beta decay and double-electron capture

Abstract: A new generation of neutrinoless double-beta decay (0νββ-decay) experiments with improved sensitivity is currently being designed and under construction. They will probe the inverted hierarchy region of the neutrino mass pattern. There is also a revived interest in the resonant neutrinoless double-electron capture (0νECEC), which also has the potential to probe lepton number conservation and to investigate the neutrino nature and mass scale. The primary concerns are the nuclear matrix elements. Clearly, the accuracy of the determination of the effective Majorana neutrino mass from the measured 0νββ-decay half-life is mainly determined by our knowledge of the nuclear matrix elements. We review recent progress achieved in the calculation of 0νββ and 0νECEC nuclear matrix elements within the quasiparticle random phase approximation. A considered self-consistent approach allows us to derive the pairing, residual interactions and the two-nucleon short-range correlations from the same modern realistic nucleon–nucleon potentials. The effect of nuclear deformation is taken into account. The possibility of evaluating 0νββ-decay matrix elements phenomenologically is discussed.