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The Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS) seeks to extend the reach of high-resolution collinear laser spectroscopy (CLS) to more exotic radionuclides. In this novel technique, ion bunches of short-lived radioisotopes are trapped between two electrostatic mirrors of a Multi-Reflection Time-of-Flight (MR-ToF) device at 30-keV kinetic energy. The same ion bunch can be probed by a spectroscopy laser for thousands of times compared to a single probing in the traditional CLS measurement scheme. Thus, the experimental sensitivity is increased by more than one to two orders of magnitude. Extensive simulations are presented, demonstrating the feasibility of high-resolution collinear laser spectroscopy (CLS) in the newly envisioned MR-ToF apparatus operating at ion energies of 30 keV. Once the mechanical design and operational parameters are optimized for the requirements of CLS, the spectral line is neither significantly broadened nor distorted by the combination of CLS and MR-ToF operation. According to the simulations, the storage efficiency and the ion–laser overlap are suitable for laser excitation of the majority of the trapped ions. In summary, >90% injection and storage efficiency, >75% ion–laser overlap and a line width approaching the natural line width of the transition of interest are reached in the simulation.

Collinear laser spectroscopy is performed on the nickel isotopes Ni58-68,70, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii Rc are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLOsat, which allows an assessment of their accuracy. We find agreement with experiment in differential radii δ⟨rc2⟩ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLOsat. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy(Δr,HFB). Collinear laser spectroscopy is performed on the nickel isotopes $^{58-68,70}$Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii $R_c$ are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLO$_{\rm sat}$, which allows an assessment of their accuracy. We find agreement with experiment in differential radii $\delta \left\langle r_\mathrm{c}^2 \right\rangle$ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLO$_{\rm sat}$. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy($\Delta r$,HFB).

The electric quadrupole moment of $^{49}$Sc was measured by collinear laser spectroscopy at CERN-ISOLDE to be $Q_{\rm s}=-0.159(8)$ $e$b, and a nearly tenfold improvement in precision was reached for the electromagnetic moments of $^{47,49}$Sc. The single-particle behavior and nucleon-nucleon correlations are investigated with the electromagnetic moments of $Z=21$ isotopes and $N=28$ isotones as valence neutrons and protons fill the distinctive $0f_{7/2}$ orbit, respectively, located between magic numbers, 20 and 28. The experimental data are interpreted with shell-model calculations using an effective interaction, and ab-initio valence-space in-medium similarity renormalization group calculations based on chiral interactions. These results highlight the sensitivity of nuclear electromagnetic moments to different types of nucleon-nucleon correlations, and establish an important benchmark for further developments of theoretical calculations., Comment: Accepted by Physics Letters B (2022)

Collinear laser spectroscopy measurements were performed on $^{69,71,73}$Ge isotopes ($Z = 32$) at ISOLDE-CERN. The hyperfine structure of the $4s^2 4p^2 \, ^3P_1 \rightarrow 4s^2 4p 5s \, ^3P_1^o$ transition of the germanium atom was probed with laser light of 269 nm, produced by combining the frequency-mixing and frequency-doubling techniques. The hyperfine fields for both atomic levels were calculated using state-of-the-art atomic relativistic Fock-space coupled-cluster calculations. A new $^{73}$Ge quadrupole moment was determined from these calculations and previously measured precision hyperfine parameters, yielding $Q_{\rm s}$ = $-$0.198(4) b, in excellent agreement with the literature value from molecular calculations. The moments of $^{69}$Ge have been revised: $\mu$ = +0.920(5) $\mu_{N}$ and $Q_{\rm s}$= +0.114(8) b, and those of $^{71}$Ge have been confirmed. The experimental moments around $N = 40$ are interpreted with large-scale shell-model calculations using the JUN45 interaction, revealing rather mixed wave function configurations, although their $g$-factors are lying close to the effective single-particle values. Through a comparison with neighboring isotones, the structural change from the single-particle nature of nickel to deformation in germanium is further investigated around $N = 40$.

The [Formula: see text] and [Formula: see text] transitions in Li-like carbon ions stored and cooled at a velocity of [Formula: see text] in the experimental storage ring (ESR) at the GSI Helmholtz Centre in Darmstadt have been investigated in a laser spectroscopy experiment. Resonance wavelengths were obtained using a new continuous-wave UV laser system and a novel extreme UV (XUV) detection system to detect forward emitted fluorescence photons. The results obtained for the two transitions are compared to existing experimental and theoretical data. A discrepancy found in an earlier laser spectroscopy measurement at the ESR with results from plasma spectroscopy and interferometry has been resolved and agreement between experiment and theory is confirmed.

International audience; Differences in mean-square nuclear charge radii of $^{100–130} \rm{Cd}$ are extracted from high-resolution collinear laser spectroscopy of the $5s^2 S_{1/2} \to 5p^2 P_{3/2}$ transition of the ion and from the $5s5p^3P_2 \to 5s6s^3S_1$ transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete $sdgh$ shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius.

Bunched-beam collinear laser spectroscopy is performed on neutron deficient ^{52,53}Fe prepared through in-flight separation followed by a gas stopping. This novel scheme is a major step to reach nuclides far from the stability line in laser spectroscopy. Differential mean-square charge radii δ⟨r^{2}⟩ of ^{52,53}Fe are determined relative to stable ^{56}Fe as δ⟨r^{2}⟩^{56,52}=-0.034(13) fm^{2} and δ⟨r^{2}⟩^{56,53}=-0.218(13) fm^{2}, respectively, from the isotope shift of atomic hyperfine structures. The multiconfiguration Dirac-Fock method is used to calculate atomic factors to deduce δ⟨r^{2}⟩. The values of δ⟨r^{2}⟩ exhibit a minimum at the N=28 neutron shell closure. The nuclear density functional theory with Fayans and Skyrme energy density functionals is used to interpret the data. The trend of δ⟨r^{2}⟩ along the Fe isotopic chain results from an interplay between single-particle shell structure, pairing, and polarization effects and provides important data for understanding the intricate trend in the δ⟨r^{2}⟩ of closed-shell Ca isotopes.

Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6) fm^{2}, providing first evidence of shape coexistence.

A marked difference in the nuclear charge radius was observed between the I^{π}=3^{+} ground state and the I^{π}=0^{+} isomer of ^{38}K and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of ⟨r_{c}^{2}⟩(^{38}K^{m})-⟨r_{c}^{2}⟩(^{38}K^{g})=0.100(6) fm^{2} was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in ^{38}K have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the N,Z=20 shell gaps, confirming the significance of cross-shell correlations in the region of ^{40}Ca.

The ground-state spins and magnetic moments of 49,51K have been measured using bunched-beam high-resolution collinear laser spectroscopy at ISOLDE CERN. For 49K a ground-state spin I=1/2 was firmly established. The observed hyperfine structure of 51K requires a spin I>1/2 and strongly suggests I=3/2. From its magnetic moment mm(51K)=0,5129(22)mN a spin-parity I=3/2+ with a dominant 1d1 3=2 hole configuration was deduced. This establishes for the first time the reinversion of the single-particle levels and illustrates the prominent role of the residual monopole interaction for single-particle levels and shell evolution. 5 pages, 3 figures ispartof: Physical Review Letters vol:110 issue:17 ispartof: location:United States status: published

The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-UV excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in 127Cd and 129Cd for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2- quadrupole moments. Remarkably, this mechanism is found to act well beyond the h11/2 shell. The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in Cd127 and Cd129 for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2- quadrupole moments. Remarkably, this mechanism is found to act well beyond the h11/2 shell. The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-UV excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in 127Cd and 129Cd for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2- quadrupole moments. Remarkably, this mechanism is found to act well beyond the h11/2 shell.

The installation of an ion–beam cooler–buncher at the ISOLDE, CERN facility has provided increased sensitivity for collinear laser spectroscopy experiments. A migration of single-particle states in gallium and in copper isotopes has been investigated through extensive measurements of ground state and isomeric state hyperfine structures. Lying beyond the N = 50 shell closure, 82Ga is the most exotic nucleus in the region to have been studied by optical methods, and is reported here for the first time.

Charge radii of all magnesium isotopes in the sd shell have been measured, revealing evolution of the nuclear shape throughout two prominent regions of assumed deformation centered on (24)Mg and (32)Mg. A striking correspondence is found between the nuclear charge radius and the neutron shell structure. The importance of cluster configurations towards N=8 and collectivity near N=20 is discussed in the framework of the fermionic molecular dynamics model. These essential results have been made possible by the first application of laser-induced nuclear orientation for isotope shift measurements.

In order to study neutron‐rich nuclides far from the valley of stability as well as long‐lived actinoids the double Penning‐trap mass spectrometer TRIGA‐TRAP has been recently installed at the research reactor TRIGA Mainz. Short‐lived neutron‐rich fission products are produced by thermal neutron‐induced fission of an actinoid target installed close to the reactor core. A helium gas‐jet system with carbon aerosol particles is used to extract the fission products to the experiment. The Penning trap system has already been commissioned. Off‐line mass measurements are routinely performed using a recently developed laser ablation ion source, and the gas‐jet system has been tested. An overview of the experiment and current status will be given.

We report the first confirmation of the predicted inversion between the pi2p3/2 and pi1f5/2 nuclear states in the nu(g)9/2 midshell. This was achieved at the ISOLDE facility, by using a combination of in-source laser spectroscopy and collinear laser spectroscopy on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments. The obtained values are mu(71Cu)=+2.2747(8)mu(N), mu(73Cu)=+1.7426(8)mu(N), and mu(75Cu)=+1.0062(13)mu(N) corresponding to spins I=3/2 for 71,73Cu and I=5/2 for 75Cu. The results are in fair agreement with large-scale shell-model calculations.

The nuclear charge radius of 11Li has been determined for the first time by high-precision laser spectroscopy. On-line measurements at TRIUMF-ISAC yielded a 7Li-11Li isotope shift (IS) of 25 101.23(13) MHz for the Doppler-free [FORMULA: SEE TEXT]transition. IS accuracy for all other bound Li isotopes was also improved. Differences from calculated mass-based IS yield values for change in charge radius along the isotope chain. The charge radius decreases monotonically from 6Li to 9Li, and then increases from 2.217(35) to 2.467(37) fm for 11Li. This is compared to various models, and it is found that a combination of halo neutron correlation and intrinsic core excitation best reproduces the experimental results.

The 2s--3s transition of (6,7,8,9)Li was studied by high-resolution laser spectroscopy using two-photon Doppler-free excitation and resonance-ionization detection. Hyperfine structure splittings and isotope shifts were determined with precision at the 100 kHz level. Combined with recent theoretical work, the changes in the nuclear-charge radii of (8,9)Li were determined. These are now the lightest short-lived isotopes for which the charge radii have been measured. It is found that the charge radii monotonically decrease with increasing neutron number from 6Li to 9Li.

We study the 2S-3S transition of (6,7)Li by high-precision laser spectroscopy using two-photon Doppler-free excitation and photoionization detection. Interferometric cross referencing to metrologic Rb 3S-5D two-photon transitions allowed measurement of the transition isotope shift and hyperfine splitting in the 3S state with precision at the 30 kHz level. The results are IS=11 453.734(30) MHz, A(3S)(6Li)=35.263(15) MHz, and A(3S)(7Li)=93.106(11) MHz. Combined with recent theoretical work, the isotope shift yields a new value for the change in squared nuclear charge radii DeltaR(2)=0.47(5) fm(2). This is compared with other work and some existing discrepancies are resolved.

135Cs/137Cs isotopic ratios were measured in the presence of high levels of 133Cs using Resonance Ionization Mass Spectrometry (RIMS). Single- and double-resonance excitation of Cs with high-resolution continuous-wave (cw) lasers along 6s 2S1/2→6p 2P3/2, 6s 2S1/2→6p 2P3/2→7d 2D5/2, and 6s 2S1/2→6p 2P3/2→8s 2S1/2 pathways were followed by photoionization with an Ar ion laser. The age of a standard burn-up sample was determined using RIMS and compared to Thermal Ionization Mass Spectrometry (TIMS). The efficiency, selectivity and isobar suppression for TIMS and RIMS has been compared. The overall RIMS efficiency was found to be ≈2×10−6 with a combined selectivity of ≈1010 for both 135Cs and 137Cs against 133Cs using the preferred single-resonance excitation scheme.

A compact diode-laser-based resonance ionization mass spectrometer has been adapted for determination of stable gadolinium isotopes. The experimental system combines narrowband resonance ionization and quadrupole mass spectrometry. It will be primarily used for precise isotope ratio determination for cosmochemical studies. Other possible applications are discussed. Excitation schemes for single- to triple-resonance ionization are presented which can be realized using solid-state diode laser systems. First studies include the isotopic abundance sensitivity of the mass spectrometer and high-resolution isotope shift measurements of all gadolinium isotopes in the 6s2 9D2→6s6p J=3 transition, which are reported for the first time.

Resonance ionization mass spectrometry (RIMS) has become a widely used technique for isotope-selective ultra-trace analysis1-4. It provides complete isobaric suppression, high overall efficiency and strongly increased isotopic selectivity in respect to conventional mass spectrometers. Still a major drawback for the application of this technique is the complexity of the experimental set-up, particularly the laser system, which restricts utilization of the technique to a small number of university and research institutes so far.

Measurements of the atomic lifetime of high‐lying 5snf 3FJ states with n = 20, 23 and 32 in the spectrum of Sr I have been performed in the 5s4d 3DJ–5snf 3FJ transitions using collinear resonance ionization spectroscopy. By rapidly chopping the laser light the population of the excited Rydberg state and hence the ionization signal of the fast moving atoms becomes a function of the radiative decay of both the initial and the excited states in the transition under study. A detailed analysis of the resulting time‐dependence of the count rate yields experimental results the radiative lifetimes for the atomic levels involved.

The application of Collinear Resonance Ionization Spectroscopy for the determination of 89,90Sr contaminations in various environmental samples is presented, demonstrating the versatility of this highly specialized and isotope‐selective ultra‐trace determination technique. Additionally to these studies we have analysed the different processes, which lead to nonselective ionization and hence cause background. Optimization of the experimental conditions resulted in a significant lowering of the detection limit to a value of 3×106 atoms of 90Sr (corresponding to an activity of 2mBq) in the presence of up to 1017 atoms of stable 88Sr. In a parallel measurement trace determination of both isotopes 89Sr and 90Sr is possible with a detection limit for 89Sr of 108 atoms. Measurements on different samples, ranging from air filter samples of 1958 up to today, soil, vegetation, milk and human urine samples as well as cooling water from nuclear power plants document the applicability and the specifications of the tec...