In recent years, significant efforts have been made to investigate the atomic structure of lawrencium (Lr, Z=103 )—the heaviest actinide element—using laser spectroscopy. This article presents the current status of the experimental search for atomic transitions in lawrencium at GSI, Darmstadt, Germany, along with the necessary developments toward achieving laser spectroscopy of this element. We have advanced the method of radiation-detected resonance ionization spectroscopy (RADRIS), which has previously enabled the first laser spectroscopic studies of nobelium. We have conducted essential preparatory studies, demonstrating that lawrencium can be efficiently evaporated from hafnium filaments. Using two-step laser resonance ionization, we scanned a spectral range of approximately 800 cm ^-1 around each of two different, theoretically predicted strong atomic transitions. Based on the measured background and the determined system efficiency, we demonstrate that our experimental setup is sensitive enough to detect these atomic transitions, albeit no atomic transitions have been observed to date.

The isomeric yield ratio (IYR) of fission products is an observable that carries relevant information about the fragments emerging from the scission of a fissioning nucleus. We report on IYR of 96,98,100Y and 100,102Nb, together with the previously reported values for 97Y and 99Nb, produced in the 28 MeV α-induced fission of 232Th at the Ion Guide Isotope Separation On-Line (IGISOL) facility of the University of Jyväskylä. We measured the IYR using two different techniques, the phase-imaging ion-cyclotron-resonance (PI-ICR) and the multiple-reflection time-of-flight mass spectrometry (MR-TOF-MS) methods. Moreover, we measured the masses of the long-lived states in 98,100Y and 100,102Nb populated via in-trap β-decay of their precursors. Since the β-decay selectively populates states with a favourable spin-parity, we could identify the measured state and show that the ground state is the low-spin state in the cases of 98Y and 100Nb, while it is the high-spin state in the cases of 100Y and 102Nb. This measurement confirms the spin-parity assignments of all the nuclei as they are reported in the NUBASE2020 evaluations, disagreeing with the assignment for 100Y reported in the ENSDF evaluation.Making also use of previously reported data, we observe an anomalously low IYR for the N=59 isotope 98Y as compared to other yttrium or neighboring niobium isotopes. This behavior is very rare across the nuclear chart and is posited to be connected to the characteristic shape coexistence of 98Y, and to the change in the charge radii of the ground and excited states in the N=58−60 region.

The FRS lon Catcher (FRS-IC) is located at the final focal plane of the Fragment Separator FRS at GSI. The FRS-IC setup is well known for high-precision experiments with stopped exotic nuclei produced by projectile fragmentation and fission. The facility consists of the cryogenic gas-filled stopping cell (CSC), an RFQ-based beamline (DISTRICT), and a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). This paper illustrates how alpha spectroscopy performed at this facility has emerged as a promising tool to unveil the nuclear structure of exotic nuclei, i.e., half- live and decay energy measurements. First studies of that kind were performed on the decay chains of 218Rn, 219Rn, 221 Ac, 220Fr, and 221.224 Th produced by projectile fragmentation of 238U. The a decay energy measurements performed and the deduced Q, values confirm the known maximum at N= 128 and the values of Q, at N= 132-133 follow the predicted increasing in Q values compared to the values for At isotopes at the same neutron number N. Further, the production rate ratio of the isomer to the ground state of 211 Po was measured. It allows an estimate of the angular momentum distribution of 211 Po fragments following fragmentation of 238 U in a "Be target at relativistic energies. In addition, the potential of mass-selected decay spectroscopy behind the MR-TOF-MS was demonstrated with short-lived 215 Po ions (11/2 = 1.78 ms). This demonstrates that the FRS-IC is a reliable setup for a spectroscopy studies and related nuclear structure studies.

Anew linear Paul trap section has been constructed to replace the existing bunching section of the radiofrequency quadrupole (RFQ) cooler-buncher at the IGISOL radioactive ion beam facility. The coolerbuncher is used to transform a continuous ion beam to temporally short bursts of ions. The new miniaturised cooler-buncher section produces significantly shorter bunches in time, required by the new Multi-Reflection Time-of-Flight Mass Spectrometer. In this article, we report on the longitudinal properties of the ion bunches and compare the results to an analytical model derived for axial distributions of ions confined in a harmonic trap at thermodynamical equilibrium with a heat bath. The new buncher configuration delivers < 75 ns full-width at half-maximum bunches with a longitudinal emittance of 200 eVns. The bunches have a full- width at half-maximum energy spread of 10 eV. Total transmission efficiency of 45%-65% has been measured from the isotope separator focal plane through the RFQ cooler-buncher, Multi-Reflection Time-of-Flight Mass Spectrometer and JYFLTRAP double Penning trap.

We report on mass measurements of three long-lived states in 114Rh performed with the JYFLTRAP Penning-trap mass spectrometer: the ground state and two isomers with estimated half-lives of about one second. The used Phase-Imaging Ion-Cyclotron-Resonance technique allowed for the discovery of a so far unknown second longlived isomer. All three states were produced directly in proton-induced fission on a uranium target, whereas only the isomeric states were populated in the beta decay of the 114Ru ground state with spin-parity 0+. We propose spin-parity assignments of (6-) for the ground state, and (3+) and (0-) for the isomers. They resolve the puzzle of anomalous fission yields of this isotope despite the existing literature assigning a low angular momentum to the ground state. The experimental evidence is further supported by a detailed analysis based on mean-field calculations with the BSkG3 model. As for many other nuclei in this mass region, considering triaxial shapes is decisive for the interpretation of low-lying states of this nucleus. The discovery of a new isomer in 114Rh and our theoretical work challenge the currently adopted spin-parity assignments in this and several other odd-odd neutron-rich Rh isotopes.

The masses of the ground and isomeric states in 124,125Ag have been measured using the phase-imaging ioncyclotron-resonance technique at the JYFLTRAP double Penning trap mass spectrometer. The ground states of 124Ag and 125Ag were found to be 30(250) keV and 250(430) keV less bound but 36 and 110 times more precise than in the Atomic Mass Evaluation 2020, respectively. The excitation energy of 124Agm, Ex = 188.2(25) keV, was determined for the first time. The new precise mass values have been utilized to study the evolution of nuclear structure via two-neutron separation energies. The impact on the astrophysical rapid neutron capture process has been investigated via neutron-capture reaction rate calculations. The precision measurements indicate a more linear trend in two-neutron separation energies and reduce the mass-related uncertainties for the neutron-capture rate of 124Ag(n, gamma ) 125Ag by a factor of around 100. The new mass values also improve the mass of 123Pd, previously measured using 124Ag as a reference.

The origin of the large angular momenta observed for fission fragments is still a question under discussion. To address this, we study isomeric yield ratios (IYRs), i.e., the relative population of two or more long-lived metastable states with different spins, of fission products. We report on IYRs of 17 isotopes produced in the 28-MeV alpha-induced fission of Th-232 at the IGISOL facility of the University of Jyvaskyla. The fissioning nuclei in this reaction are U-233,U-234,U-235*. We compare our data to IYRs from thermal neutron-induced fission of U-233 and U-235, and we observe statistically significant larger IYRs in the Th-232(alpha, f) reaction, where the average compound nucleus (CN) spin is 7.7 h, than in U-233,U-235(n(th), f), with average spins of 2.6 and 3.6 h, respectively. To assess the influence of the excitation energy, we study literature data of IYRs from photon-induced fission reactions, and find that, within current uncertainties, the IYRs indicate no dependency of the CN excitation energy. We conclude that the different IYRs seem to be due to the different CN spins alone. This would imply that the fission fragment angular momentum only partly comes from the fission process itself and is, in addition, influenced by the angular momentum present in the CN.

A direct measurement of the ground-state-to-ground-state electron-capture decay Q (QEC) value of 97Tc has been conducted employing the high-resolving-power phase-imaging ion-cyclotron-resonance technique with the double Penning trap mass spectrometer JYFLTRAP. The resulting QEC value for 97Tc is 324.82(21) keV, exhibiting a precision approximately 19 times higher than the value adopted in the newest Atomic Mass Evaluation (AME2020) and differing by 1.2 sigma. Furthermore, by combining this refined Q value with nuclear energy-level data for the decay-daughter 97Mo, a potential ultralow Q-value transition 97Tc (9/2+, ground state) -> 97Mo & lowast; [320(1) keV] was detected. The ground-state-to-excited-state electron-capture decay Q value (Q & lowast;EC) of this transition was determined to be 4.8(10) keV, confirming it to be energetically allowed with a confidence level of exceeding 4 sigma. The captures of electrons occupying the L and higher shells for this transition are energetically allowed, giving a value of 2.0(10) keV for the closest distance of Q & lowast; EC to the allowed binding energy of the L1 shell. To predict partial half-lives and energy-release distributions for this transition, the atomic self-consistent many-electron Dirac-Hartree-Fock-Slater method and the nuclear shell model have been employed. Dominant correction terms such as exchange and overlap corrections, as well as shake-up and shake-off effects, were included in the final results. Moreover, in the case of a possible allowed transition, the normalized distribution of released energy in the electron-capture decay of 97Tc to the excited 320-keV state of 97Mo, is compared with that of 163Ho, which is being used for electron-neutrino-mass determination. A pseudoexperiment technique was introduced to calculate error propagation in half-life and the 68% confidence interval for normalized energy distributions.

We report on the masses and hyperfine structure of ground and isomeric states in ^114,116,118,120Ag isotopes, measured with the phase-imaging ion-cyclotron-resonance technique (PI-ICR) with the JYFLTRAP mass spectrometer and the collinear laser spectroscopy beamline at the Ion Guide Isotope Separator On-Line (IGISOL) facility, Jyväskylä, Finland. We measured the masses and excitation energies, electromagnetic moments, and charge radii, and firmly established the nuclear spins of the long-lived states. A new isomer was discovered in ^118Ag and the half-lives of ^118Ag long-lived states were reevaluated. We unambiguously pinned down the level ordering of all long-lived states, placing the inversion of the I = 0^- and I = 4^+ states at A = 118 (N = 71). Lastly, we compared the electromagnetic moments of each state to empirical single-particle moments to identify the dominant configuration where possible.

High-precision mass measurements of exotic ^{95-97}Ag isotopes close to the N=Z line have been conducted with the JYFLTRAP double Penning trap mass spectrometer, with the silver ions produced using the recently commissioned inductively heated hot cavity catcher laser ion source at the Ion Guide Isotope Separator On-Line facility. The atomic mass of ^{95}Ag was directly determined for the first time. In addition, the atomic masses of β-decaying 2^{+} and 8^{+} states in ^{96}Ag have been identified and measured for the first time, and the precision of the ^{97}Ag mass has been improved. The newly measured masses, with a precision of ≈1  keV/c^{2}, have been used to investigate the N=50 neutron shell closure, confirming it to be robust. Empirical shell-gap and pairing energies determined with the new ground-state mass data are compared with the state-of-the-art ab initio calculations with various chiral effective field theory Hamiltonians. The precise determination of the excitation energy of the ^{96m}Ag isomer in particular serves as a benchmark for ab initio predictions of nuclear properties beyond the ground state, specifically for odd-odd nuclei situated in proximity to the proton dripline below ^{100}Sn. In addition, density functional theory calculations and configuration-interaction shell-model calculations are compared with the experimental results. All theoretical approaches face challenges to reproduce the trend of nuclear ground-state properties in the silver isotopic chain across the N=50 neutron shell and toward the proton dripline.

We report on new precision mass measurements of neutron-rich $^{137}$Sb and $^{136-142}$I isotopes from the JYFLTRAP double Penning trap mass spectrometer. We confirm the value from the previous Penning-trap measurement of $^{137}$Sb at the Canadian Penning Trap and therefore rule out the conflicting result from the Experimental Storage Ring. The ground state and isomer in $^{136}$I were resolved and measured directly for the first time. The isomer excitation energy, $E_x = 215.1(43)$ keV, agrees with the literature but is three times more precise. The measurements have improved the precision of the mass values and confirmed previous results in the majority of cases. However, for $^{138,140}$I the results differ by 17(6) keV and 23(12) keV, respectively. This could be explained by an unresolved contamination or different ratio of unresolved isomeric states in the case of $^{140}$I.

We report on a set of high-precision measurements of nuclear binding and excitation energies, as well as nuclear spins, magnetic dipole and electric quadrupole moments of neutron-rich silver isotopes, 113−123Ag. The measurements were performed using the JYFLTRAP mass spectrometer and the collinear laser spectroscopy beamline at the Ion Guide Isotope Separator On-Line (IGISOL) facility. For the first time, we can firmly establish the ordering of the long-lived Iπ=1/2−,7/2+ states in these isotopes, and pin down the inversion of these two levels at either A=121(N=74) or A=123(N=76). We compare these findings to calculations performed with density functional theory (DFT), from which we establish the crucial role that the spin-orbit strength and time-odd mean fields play in the simultaneous description of electromagnetic moments and nuclear binding.

The quantum-mechanical nuclear-shell structure determines the stability and limits of the existence of the heaviest nuclides with large proton numbers Z ≳ 100 (refs. 1-3). Shell effects also affect the sizes and shapes of atomic nuclei, as shown by laser spectroscopy studies in lighter nuclides4. However, experimental information on the charge radii and the nuclear moments of the heavy actinide elements, which link the heaviest naturally abundant nuclides with artificially produced superheavy elements, is sparse5. Here we present laser spectroscopy measurements along the fermium (Z = 100) isotopic chain and an extension of data in the nobelium isotopic chain (Z = 102) across a key region. Multiple production schemes and different advanced techniques were applied to determine the isotope shifts in atomic transitions, from which changes in the nuclear mean-square charge radii were extracted. A range of nuclear models based on energy density functionals reproduce well the observed smooth evolution of the nuclear size. Both the remarkable consistency of model prediction and the similarity of predictions for different isotopes suggest a transition to a regime in which shell effects have a diminished effect on the size compared with lighter nuclei.

Molecules containing short-lived, radioactive nuclei are uniquely positioned to enable a wide range of scientific discoveries in the areas of fundamental symmetries, astrophysics, nuclear structure, and chemistry. Recent advances in the ability to create, cool, and control complex molecules down to the quantum level, along with recent and upcoming advances in radioactive species production at several facilities around the world, create a compelling opportunity to coordinate and combine these efforts to bring precision measurement and control to molecules containing extreme nuclei. In this manuscript, we review the scientific case for studying radioactive molecules, discuss recent atomic, molecular, nuclear, astrophysical, and chemical advances which provide the foundation for their study, describe the facilities where these species are and will be produced, and provide an outlook for the future of this nascent field.

Abstract High-resolution collinear laser spectroscopy has been performed on singly charged ions of $$^{234,235,238}$$ 234 , 235 , 238 U at the IGISOL facility of the Accelerator Laboratory, University of Jyväskylä, in Finland. Ten ionic transitions from the $$^{4}\hbox {I}_{9/2}$$ 4 I 9 / 2 and $$^{6}\hbox {L}_{11/2}$$ 6 L 11 / 2 ground and first excited states were measured in the 300 nm wavelength range, improving the precision of the hyperfine parameters of the lower states in addition to providing newly measured values for the upper levels. Isotope shifts of the analyzed transitions are also reported for $$^{234,235}$$ 234 , 235 U with respect to $$^{238}$$ 238 U.

High-resolution laser spectroscopy can be used to precisely measure atomic hyperfine structures and shifts in spectral lines. These nuclear perturbations of the atomic structure provide insight into the bulk properties of nuclei as well as the intricate details of the nucleon–nucleon interactions inside the atomic nucleus. Collinear laser spectroscopy in particular allows for the extraction of nuclear moments and changes in the mean-square charge radii with high precision. We provide an overview of the manner in which collinear laser spectroscopy is currently implemented at radioactive ion beam facilities. Through examples, we illustrate how this method gives access to direct and nuclear model-independent evidence for changes in nuclear spins, electromagnetic moments and nuclear radii caused by structural changes in atomic nuclei.

The absolute mass of ^84Sr was determined using the phase-imaging ion-cyclotron-resonance technique with the JYFLTRAP double Penning trap mass spectrometer. A more precise value for the mass of ^84Sr is essential for providing potential indications of physics beyond the Standard Model through high-precision isotope shift measurements of Sr atomic transition frequencies. The mass excess of ^84Sr was refined to be -80649.229(37) keV/c^2 from high-precision cyclotron-frequency-ratio measurements with a relative precision of 4.8× 10^-10 . The obtained mass-excess value is in agreement with the adopted value in the Atomic Mass Evaluation 2020, but is 30 times more precise. With this new value, we confirm the previously observed nonlinearity in the study of the isotope shift of strontium. Moreover, the double-beta ( 2β ^+ ) decay Q value of ^84Sr was directly determined to be 1790.115(37) keV, and the precision was improved by a factor of 30.

Isomers close to the doubly magic nucleus 78Ni (Z=28, N=50) provide essential information on the shell evolution and shape coexistence far from stability. The existence of a long-lived isomeric state in 76Cu has been debated for a long time. We have performed high-precision mass measurements of 76Cu with the JYFLTRAP double Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line facility and confirm the existence of such an isomeric state with an excitation energy Ex=64.8(25) keV. Based on the ratio of detected ground- and isomeric-state ions as a function of time, we show that the isomer is the shorter-living state previously considered as the ground state of 76Cu. The result can potentially change the conclusions made in previous works related to the spin-parity and charge radius of the 76Cu ground state. Additionally, the new 76Cu(n,γ) reaction Q-value has an impact on the astrophysical rapid neutron-capture process.

The first direct determination of the ground-state-to-ground-state β ^- -decay Q-value of ^77 As to ^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 Se from γ -ray spectroscopy, the ground-state-to-excited-state Q-value of the transition ^77 As (3/2 ^- , ground state) → ^77 Se ^* (5/2 ^+ , 680.1035(17) keV) was refined to be 4.360(70) keV. We confirm that this potential low Q-value β ^- -decay transition for neutrino mass determination is energetically allowed at a confidence level of about 60 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 years for this first-forbidden non-unique transition. Since the half-life of ^77 As is only ≈ 2 days, usage of it as source for rare-event experiments searching for the electron antineutrino mass would be challenging.

The multinucleon transfer (MNT) reaction approach was successfully employed for the first time to measure the isomeric ratios (IRs) of 211Po isomer (25/2+) and its ground state (9/2+) at the IGISOL facility using a 945 MeV 136Xe beam impinged on 209Bi and natPb targets. The dominant production of isomers compared to the corresponding ground states was consistently revealed in the α-decay spectra. Deduced IR of 211Po populated through the 136Xe+natPb reaction was found to have an enhancement of ≈1.8-times than that observed for the 136Xe+209Bi. State-of-the-art Langevin-type model calculations have been utilized to estimate the spin distribution of an MNT residue. The computations qualitatively corroborate with the considerable increase in the IRs of 211Po produced from 136Xe+natPb compared to 136Xe+209Bi. Theoretical investigations indicate a weak dependence of target spin on the IRs. The enhancement of the 211Po isomer in the 136Xe+natPb over 136Xe+209Bi can be attributed to the different proton (p)-transfer production routes. Estimations demonstrate an increment in the angular momentum transfer, favorable for isomer production, with increasing projectile energy. Comparative analysis reveals the two entrance channel parameters, projectile mass and p-transfer channels, strongly influencing the population of the high-spin isomer of 211Po (25/2+). This letter reports the first experimental and theoretical study on the IRs of nuclei formed via two different channels of MNT reactions.