Precision mass measurements of 104Y, 106Zr, 104,104m,109Nb, and 111,112Mo have been performed with the JYFLTRAP double Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line ...facility. The order of the long-lived states in 104Nb was unambiguously established. The trend in two-neutron separation energies around the N=66 neutron midshell appeared to be steeper with respect to the Atomic Mass Evaluation 2020 extrapolations for the 39Y and 40Zr isotopic chains and less steep for the 41Nb chain, indicating a possible gap opening around Z=40. The experimental results were compared to the BSkG2 model calculations performed with and without vibrational and rotational corrections. All of them predict two low-lying minima for 106Zr. While the unaltered BSkG2 model fails to predict the trend in two-neutron separation energies, selecting the more deformed minima in calculations and removing the vibrational correction, the calculations are more in line with experimental data. The same is also true for the 21+ excitation energies and differences in charge radii in the Zr isotopes. The results stress the importance of improved treatment of collective corrections in large-scale models and further development of beyond-mean-field techniques.
The in-gas laser ionization and spectroscopy (IGLIS) technique is used to produce and to investigate short-lived radioactive isotopes at on-line ion beam facilities. In this technique, the nuclear ...reaction products recoiling out of a thin target are thermalized and neutralized in a high-pressure noble gas, resonantly ionized by the laser beams in a two-step process, and then extracted from the ion source to be finally accelerated and mass separated. Resonant ionization of radioactive species in the supersonic gas jet ensures very high spectral resolution because of essential reduction of broadening mechanisms. To obtain the maximum efficiency and the best spectral resolution, properties of the supersonic jet and the laser beams must be optimized. To perform these studies a new off-line IGLIS laboratory, including a new high-repetition-rate laser system and a dedicated off-line mass separator, has been commissioned. In this article, the specifications of the different components necessary to achieve optimum conditions in laser-spectroscopy studies of radioactive beams using IGLIS are discussed and the results of simulations are presented.
The method of laser spectroscopy in supersonic gas jets was proposed for high-resolution and high-efficiency in-gas laser ionization and spectroscopy studies of short-lived nuclei. The flow ...properties of such supersonic gas jets have been characterized under off-line conditions. Planar laser-induced fluorescence spectroscopy of seeded copper atoms has been applied to nonintrusively measure velocity, temperature, and relative density profiles of gas jets formed by different de Laval nozzles. For validation, planar laser-induced fluorescence spectroscopy was applied on supersonic free jets with well-known flow parameters. The performance of the in-gas-jet laser spectroscopy method is determined by the achievable spectral resolution, which requires an optimization and a precise manufacturing of the nozzle inner contour as well as a pressure matching of the background medium at the nozzle exit. Our studies now enable a thorough understanding and quantification of these requirements and a determination of the final performance of the in-gas-jet method. Additionally, a comparison between the experimental results and the numerical calculations was performed for the temperature, velocity, and Mach number profiles of underexpanded and quasiuniform jets formed by a de Laval nozzle.
Abstract The first direct determination of the ground-state-to-ground-state $${\beta ^{-}}$$ β - -decay Q -value of $$^{77}$$ 77 As to $$^{77}$$ 77 Se was performed by measuring their atomic mass ...difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The resulting Q -value is 684.463(70) keV, representing a remarkable 24-fold improvement in precision compared to the value reported in the most recent Atomic Mass Evaluation (AME2020). With the significant reduction of the uncertainty of the ground-state-to-ground-state Q -value and knowledge of the excitation energies in $$^{77}$$ 77 Se from $$\gamma $$ γ -ray spectroscopy, the ground-state-to-excited-state Q -value of the transition $$^{77}$$ 77 As (3/2 $$^{-}$$ - , ground state) $$\rightarrow $$ → $$^{77}$$ 77 Se $$^{*}$$ ∗ (5/2 $$^{+}$$ + , 680.1035(17) keV) was refined to be 4.360(70) keV. We confirm that this potential low Q -value $${\beta ^{-}}$$ β - -decay transition for neutrino mass determination is energetically allowed at a confidence level of about 60 $$\sigma $$ σ . Nuclear shell-model calculations with two well-established effective Hamiltonians were used to estimate the partial half-life for the low Q -value transition. The half-life was found to be of the order of 10 $$^{9}$$ 9 years for this first-forbidden non-unique transition. Since the half-life of $$^{77}$$ 77 As is only $$\approx $$ ≈ 2 days, usage of it as source for rare-event experiments searching for the electron antineutrino mass would be challenging.
Radio-frequency (RF) ion guides, also known as Linear Paul Traps, are powerful devices to efficiently transport ion beams from high to low pressure regions while keeping good ion optical properties. ...A set of ion guides comprising three different RF quadrupole (RFQ) structures has been designed using ion-trajectory simulations to improve the performance of the In-Gas Laser Ionizations and Spectroscopy (IGLIS) technique currently under development at KU Leuven. Results of the commissioning tests for the total transport efficiency and transient time through the ion guides as well as the longitudinal energy spread and transverse emittance are found to be in agreement with ion trajectory simulations considering a realistic ion-atom interaction potential.
A new automated control system is developed for the In-Gas Laser Ionization and Spectroscopy (IGLIS) laboratory at KU Leuven. The IGLIS Control System is capable of stabilizing a narrowband ...single-mode tunable diode laser with a standard deviation of 1.14 MHz. Furthermore, the system controls and synchronizes all data acquisition for multiple techniques from resonant laser spectroscopy in gas cell or in gas jet to atomic Planar-Laser Induced Fluorescence (PLIF) spectroscopy of copper atoms seeded in a supersonic gas jet. The IGLIS Control System is validated by measuring the hyperfine splitting parameters of the ground state transition at 327 nm in 63Cu.
The in-gas-jet laser spectroscopy method relies on the production of uniform and low-temperature gas jets to fully resolve the atomic hyperfine structure and efficiently determine fundamental nuclear ...properties of short-lived isotopes from, e.g., the hardly accessible actinide and transactinide elements. In this article we present the studies devoted to designing, producing, and characterizing the flow properties of a convergent-divergent (de Laval) hypersonic nozzle with a superior performance for laser spectroscopy applications. A novel flow mapping technique, based on resonance ionization spectroscopy (RIS), has been employed to characterize the local flow properties of an argon gas jet formed by this nozzle, revealing a 61.5-mm long, highly collimated atomic jet at a uniform low temperature of 16.6(5) K Mach 8.11(12) that will enable laser spectroscopy experiments on heavy-exotic nuclei with an unprecedented spectral resolution and a high efficiency. These results have been compared with those obtained by planar laser induced fluorescence spectroscopy (PLIFS) studies and show a good agreement between the two techniques and a significant improvement in efficiency of the RIS mapping method with respect to PLIFS. The data are compared to state-of-the-art fluid-dynamics calculations that were carried out to obtain the nozzle contour and simulate its performance, as well as to explain the observation of a possible onset of argon nucleation.
Results of offline commissioning tests for a new dedicated gas cell for the Mass Analysing Recoil Apparatus (MARA) Low-Energy Branch are reported. Evacuation time, ion survival and transport ...efficiency in helium buffer gas were characterized with a radioactive 223Raα-recoil source. Suppression of the ion signal, originating from non-neutralized species in the gas cell, was explored with 219Rn ions, the daughter recoil of 223Ra, as a function of voltage applied to one of the ion-collector electrodes. Two-step laser resonance ionization of stable tin isotopes produced inside the gas cell from a heated bronze filament was demonstrated, and broadening of the atomic resonances in argon buffer gas was studied. These tests indicate the suitability of the new gas cell for future in-gas laser spectroscopy studies of exotic nuclei at the Accelerator Laboratory of the University of Jyväskylä.
Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic ...multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.