Mainly because of its long half-life and despite its scientific relevance, spectroscopic measurements of $^{176}$Lu forbidden $\beta$-decays are very limited and lack formulation of shape factors. A direct precise measurement of its $Q$ value is also presently unreported. In addition, the description of forbidden decays provides interesting challenges for nuclear theory. The comparison of precise experimental results with theoretical calculations for these decays can help to test underlying models and can aid the interpretation of data from other experiments.

Z. Meisel, ∗ A. Hamaker, 3 G. Bollen, 4 B.A. Brown, 3, 5 M. Eibach, K. Gulyuz, 7 C. Izzo, 3, † C. Langer, F. Montes, 5 W.-J Ong, D. Puentes, 3 M. Redshaw, 2 R. Ringle, R. Sandler, 7 H. Schatz, 3, 5 S. Schwarz, C. S. Sumithrarachchi, A. A. Valverde, ‡ and I. T. Yandow 3 Institute of Nuclear & Particle Physics, Department of Physics & Astronomy, Ohio University, Athens, Ohio 45701, USA National Superconducting Cyclotron Laboratory, East Lansing, Michigan 48824, USA Department of Physics & Astronomy, Michigan State University, East Lansing, Michigan 48824, USA Facility for Rare Isotope Beams, East Lansing, Michigan 48824, USA Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements, Michigan State University, East Lansing, Michigan 48824, USA GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany Department of Physics, Central Michigan University, Mount Pleasant, MI 48859, USA Department of Energy Technology, University of Applied Science Aachen, Campus Jülich, 52428 Jülich, Germany Lawrence Livermore National Laboratory, Livermore, California 94550, USA Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA (Dated: October 28, 2021)

Direct mass measurements in the region of the heaviest elements were performed with the Penning-trap mass spectrometer SHIPTRAP at GSI Darmstadt. Utilizing the phase-imaging ion-cyclotron-resonance massspectrometry technique, the atomic masses of 251No (Z = 102), 254Lr (Z = 103), and 257Rf (Z = 104) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of 254No and 255,256Lr were improved by more than one order of magnitude. Relative statistical uncertainties as low as delta m/m approximate to 10-9 were achieved. Mass resolving powers of 11 000 000 allowed resolving long-lived low-lying isomeric states from their respective ground states in 251,254No and 254,255Lr. This provided an unambiguous determination of the binding energies for odd-A and odd-odd nuclides previously determined only indirectly from decay spectroscopy.

Background: The quadratic isobaric multiplet mass equation (IMME) has been very successful at predicting the masses of isobaric analog states in the same multiplet, while its coefficients are known to follow specific trends as functions of mass number. The Atomic Mass Evaluation 2016 [Chin. Phys. C 41, 030003 (2017)] V-44 mass value results in an anomalous negative c coefficient for the IMME quadratic term; a consequence of large uncertainty and an unresolved isomeric state. The b and c coefficients can provide useful constraints for construction of the isospin-nonconserving Hamiltonians for the pf shell. In addition, the excitation energy of the 0(+), T = 2 level in V-44 is currently unknown. This state can be used to constrain the mass of the more exotic Cr-44. Purpose: The aim of the experimental campaign was to perform high-precision mass measurements to resolve the difference between V-44 isomeric and ground states, to test the IMME using the new ground state mass value and to provide necessary ingredients for the future identification of the 0(+), T = 2 state in V-44. Method: High-precision Penning trap mass spectrometry was performed at LEBIT, located at the National Superconducting Cyclotron Laboratory, to measure the cyclotron frequency ratios of [(VO)-V-44g,m](+) versus [(SCO)-S-32](+), a well-known reference mass, to extract both the isomeric and ground state masses of V-44. Results: The mass excess of the ground and isomeric states in V-44 were measured to be -23 804.9(80) keV/c(2) and -23 537.0(55) keV/c(2), respectively. This yielded a new proton separation energy of S-p = 1 773(10) keV. Conclusion: The new values of the ground state and isomeric state masses of V-44 have been used to deduce the IMME b and c coefficients of the lowest 2(+) and 6(+) triplets in A = 44. The 2(+) c coefficient is now verified with the IMME trend for lowest multiplets and is in good agreement with the shell-model predictions using charge-dependent Hamiltonians. The mirror energy differences were determined between V-44 and Sc-44, in line with isospin-symmetry for this multiplet. The new value of the proton separation energy determined, to an uncertainty of 10 keV, will be important for the determination of the 0(+), T = 2 state in V-44 and, consequently, for prediction of the mass excess of Cr-44.

Direct high-precision mass spectrometry of the heaviest elements with SHIPTRAP, at GSI in Darmstadt, Germany, requires high efficiency to deal with the low production rates of such exotic nuclides. A second-generation gas stopping cell, operating at cryogenic temperatures, was developed and recently integrated into the relocated system to boost the overall efficiency. Offline measurements using 223Ra and 225Ac recoil-ion sources placed inside the gas volume were performed to characterize the gas stopping cell with respect to purity and extraction efficiency. In addition, a first online test using the fusion-evaporation residue 254No was performed, resulting in a combined stopping and extraction efficiency of 33(5)%. An extraction time of 55(44)ms was achieved. The overall efficiency of SHIPTRAP for fusion-evaporation reaction products was increased by an order of magnitude to 6(1)%. This will pave the way for direct mass spectrometry of heavier and more exotic nuclei, eventually in the region of superheavy elements with proton numbers Z⩾104.

The Isobaric Multiplet Mass Equation (IMME) has been successful at predicting the masses of isobaric analogue states in the same multiplet, while its coefficients are known to follow trends as functions of mass number. The Atomic Mass Evaluation 2016 [Chin. Phys. C 41, 030003 (2017)] ^44V mass value results in an negative c coefficient for the IMME quadratic term. The b and c coefficients can provide constraints for construction of the isospin-nonconserving (INC) Hamiltonians for the pf shell. The excitation energy of the 0^+, T=2 level in ^44V is currently unknown and can be used to constrain the ^44Cr mass. The aim of the experiment was to perform high-precision mass measurements to resolve the difference between ^44V isomeric and ground states, to test the IMME, and to provide ingredients for identifying the 0^+, T=2 state in ^44V. High-precision Penning trap mass spectrometry was performed at LEBIT, to measure the cyclotron frequency ratios of [^44g,mVO]^+ versus [^32SCO]^+, a reference mass, to extract both the isomeric and ground state masses of ^44V. The mass excess of the ground and isomeric states in ^44V were measured to be -23804.9(80) keV/c^2 and -23 537.0(55) keV/c^2. This yielded a new proton separation energy of S_p = 1 773(10) keV. The new mass values of ^44V have been used to deduce the IMME b and c coefficients of the lowest 2^+ and 6^+ triplets in A=44. The 2^+ c coefficient is verified with the IMME trend and agrees with the shell-model predictions using charge-dependent Hamiltonians. The mirror energy differences were determined between ^44V and ^44Sc, in line with isospin-symmetry. The new value of the proton separation energy determined will be important for the determination of the 0^+, T=2 state in ^44V and for prediction of the mass of ^44Cr.

Background: The understanding and description of forbidden decays provides interesting challenges for nuclear theory. These calculations could help to test underlying nuclear models and interpret experimental data. Purpose: Compare a direct measurement of the $^{138}$La $\beta$-decay $Q$ value with the $\beta$-decay spectrum end-point energy measured by Quarati et al. using LaBr$_3$ detectors [Appl. Radiat. Isot. 108, 30 (2016)]. Use new precise measurements of the $^{138}$La $\beta$-decay and electron capture (EC) $Q$ values to improve theoretical calculations of the $\beta$-decay spectrum and EC probabilities. Method: High-precision Penning trap mass spectrometry was used to measure cyclotron frequency ratios of $^{138}$La, $^{138}$Ce and $^{138}$Ba ions from which $\beta$-decay and EC $Q$ values for $^{138}$La were obtained. Results: The $^{138}$La $\beta$-decay and EC $Q$ values were measured to be $Q$ = 1052.42(41) keV and $Q_{EC}$ = 1748.41(34) keV, improving the precision compared to the values obtained in the most recent atomic mass evaluation [Wang, et al., Chin. Phys. C 41, 030003 (2017)] by an order of magnitude. These results are used for improved calculations of the $^{138}$La $\beta$-decay shape factor and EC probabilities. New determinations for the $^{138}$Ce 2EC $Q$ value and the atomic masses of $^{138}$La, $^{138}$Ce, and $^{138}$Ba are also reported. Conclusion: The $^{138}$La $\beta$-decay $Q$ value measured by Quarati et al. is in excellent agreement with our new result, which is an order of magnitude more precise. Uncertainties in the shape factor calculations for $^{138}$La beta-decay using our new $Q$ value are reduced by an order of magnitude. Uncertainties in the EC probability ratios are also reduced and show improved agreement with experimental data.

We discuss the motivation and technique of Penning trap mass spectrometry applied to radioactive 44V and 44mV, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. A complementary measurement of these nuclides, performed at the CSRe in Lanzhou, China, was recently published, but with errors several times larger than obtainable for a short-lived radionuclide in a Penning trap. Interpretation of the higher precision results is ongoing and a full accounting of this measurement is anticipated in the coming months.

Nuclear structure and astrophysics studies rely heavily on precision mass measurements of rare isotopes. However, many of these isotopes far from the valley of stability can only be produced at very low rates, which are incompatible with the destructive measurement techniques used by rare isotope Penning trap mass spectrometry facilities. To this end, the Low Energy Beam and Ion Trap facility at the National Superconducting Laboratory is in the process of commissioning a single ion Penning trap (SIPT) mass spectrometer that relies on the non-destructive narrowband Fourier Transform ion cyclotron resonance technique. SIPT is the first Penning trap designed to perform mass measurements of rare isotopes produced via projectile fragmentation at rates on the order of one ion per day. The system details and cryogenic detection design, as well as results from the room and cryogenic temperature commissioning, are discussed at length.

Gas catchers are widely used to thermalize nuclear reaction products and subsequently extract them for precision measurements. However, impurities in the inert stopping gas can chemically react with the ions and thus influence the extraction efficiency. So far, chemical reactions in the gas-catcher have not been investigated in detail. Therefore, we are currently building a new setup to develop Chemical Isobaric SEparation (CISE) with the aim to understand the chemistry inside the gas-catcher and to explore its potential as a new technique for separation of isobars. In this paper, we give a short description of the setup together with the ion transportation studies performed via ion-optics simulations.

This corrects the article DOI: 10.1103/PhysRevLett.120.032701.

We propose to perform a high-precision measurement of the 18Ne superallowed β-decay QEC-value using the Penning-trap mass spectrometer ISOLTRAP. The result will be used in the determination of the 18Ne corrected -value. Despite showing the biggest deviation to the world average the 18Ne corrected value is among the least precisely known. We propose to measure the Q-value of the ground-state transition to a precision of 20 eV. The contribution of the QEC-value uncertainty to the uncertainty in value would then be pushed below the contribution of the half-life, which was recently measured at TRIUMF. Thus, the precision and accuracy of the ! -value would be entirely limited by the contribution from the branching ratio measurement, and the QEC-value, so far a combination of a Penning-trap mass and one resulting from reaction measurements, would be set on solid ground. These data provide a test of the conserved vector current hypothesis and of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. Requested shifts: 8 Ft Ft

One of the most important atomic properties influencing elements chemical behaviour is the energy required to remove its outermost electron: the first ionization potential (IP). The determination of this basic atomic property is challenging for the transfermium elements with Z > 100. Recently, Rydberg states have been observed in nobelium (No, Z = 102) inside a buffer gas cell. The buffer gas environment influences the energy of the Rydberg levels and thus the IP extracted from analysing the Rydberg series. Therefore, laser resonance ionization spectroscopy in a buffer gas cell was employed to determine the IP of its chemical homologue, ytterbium (Yb, Z = 7 0) at different buffer gas pressures to characterize the systematics arising from the buffer gas environment.

The region near Z=28, N=40 is a subject of great interest for nuclear structure studies due to spectroscopic signatures in $^{68}$Ni suggesting a subshell closure at N=40. Trends in nuclear masses and their derivatives provide a complementary approach to shell structure investigations via separation energies. Penning trap mass spectrometry has provided precise measurements for a number of nuclei in this region, however a complete picture of the mass surfaces has so far been limited by the large uncertainty remaining for nuclei with N > 40 along the iron and cobalt chains. Here we present the first Penning trap measurements of $^{68,69}$Co, performed at the Low-Energy Beam and Ion Trap facility at the National Superconducting Cyclotron Laboratory. In addition, we perform ab initio calculations of ground state and two-neutron separation energies of cobalt isotopes with the valence-space in-medium similarity renormalization group approach based on a particular set of two- and three-nucleon forces which predict saturation in infinite matter. We discuss the importance of these measurements and calculations for understanding the evolution of nuclear structure near $^{68}$Ni.

We report the mass measurement of ^{56}Cu, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of ^{56}Cu is critical for constraining the reaction rates of the ^{55}Ni(p,γ) ^{56}Cu(p,γ) ^{57}Zn(β^{+}) ^{57}Cu bypass around the ^{56}Ni waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, ME=-38626.7(7.1)  keV, is a factor of 30 more precise than the extrapolated value suggested in the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)CPCHCQ1674-113710.1088/1674-1137/36/12/003], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C 41, 030003 (2017)CPCHCQ1674-113710.1088/1674-1137/41/3/030003]. The new experimental average, using our new mass and the value from AME2016, is used to calculate the astrophysical ^{55}Ni(p,γ) and ^{56}Cu(p,γ) forward and reverse rates and perform reaction network calculations of the rp process. These show that the rp-process flow redirects around the ^{56}Ni waiting point through the ^{55}Ni(p,γ) route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

Using high-precision Penning trap mass spectrometry at the Low Energy Beam and Ion Trap facility at the National Superconducting Cyclotron Laboratory we have measured the Q values of the fourth-order beta decay and electron capture of V-50 and the double electron capture Q value of Cr-50 with the results Q(beta)(V-50) = 1038.1(l)keV, Q(EC)(V-50) = 2208.7(1)keV, and Q(2EC)(Cr-50) = 1170.5(1) keV In addition, we have measured the atomic masses of Ti-46,Ti-47,Ti-49,Ti-50, V-50,V-51, and Cr-50,Cr-52-54, reducing uncertainties by factors of up to three compared with the most recent atomic mass evaluation (AME2016) [Chin. Phys. C 41, 030003 (2017)]. Our results are in good agreement with AME2016 for Ti-46,Ti-47,Ti-49,Ti-50 and Cr-50,Cr-54 and show deviations of up to similar to 1 keV (2.5 sigma) for 50HTC/SUPTAG'FORTITLEHTC_RETAIN(51)V and Cr-50,Cr-54.