Yb Nuclei Research Articles

Microscopic study of low-lying energy levels and electromagnetic properties in even–even $$^{168-178}$$Yb nuclei

Microscopic study of low-lying energy levels and electromagnetic properties in even–even $$^{168-178}$$Yb nuclei

Precision Determination of Isotope Shifts in Ytterbium and Implications for New Physics.

We report measurements of isotope shifts for the five spinless Yb isotopes on the 6s^{2} ^{1}S_{0}→5d6s ^{1}D_{2} transition using Doppler-free two-photon spectroscopy. We combine these data with existing measurements on two transitions in Yb^{+} [Counts etal. Phys. Rev. Lett. 125, 123002 (2020)PRLTAO0031-900710.1103/PhysRevLett.125.123002], where deviation from King-plot linearity showed hints of a new bosonic force carrier at the 3σ level. The combined data strongly reduce the significance of the new-physics signal. We show that the observed nonlinearity in the joint Yb/Yb^{+} King-plot analysis can be accounted for by the deformation of the Yb nuclei.

Theoretical study of YbOH173 to search for the nuclear magnetic quadrupole moment

CP-violating interaction of the nuclear magnetic quadrupole moment (MQM) with electrons in the ytterbium mono-hydroxide molecule, $^{173}$YbOH, is considered. Both the magnetic quadrupole moment (MQM) of the $^{173}$Yb nucleus and the molecular interaction constant WM are estimated. Electron correlation effects are taken into account within the relativistic Fock-space coupled cluster method. Results are interpreted in terms of the strength constants of CP-violating nuclear forces, neutron EDM, QCD vacuum angle $\theta$, quark EDM and chromo-EDM.

High electron mobility with significant spin-orbit coupling in rock-salt YbO epitaxial thin film

We studied the optical and electrical properties of ytterbium monoxide (YbO) epitaxial thin films with unusual Yb2+ (4f145d0) valence grown by the pulsed laser deposition method. The narrow bandgap of 0.25 eV and the large crystal field splitting of 5d orbitals in YbO determined from absorption spectra were consistent with the chemical trends of ytterbium monochalcogenides (YbChs). Electrical resistivity was tunable upon electron doping via introduction of oxygen vacancies. Electron mobility at room temperature increased up to ∼13 cm2 V−1 s−1 with increasing electron carrier density. The heavily electron-doped YbO showed weak antilocalization at low temperature, suggesting significant spin-orbit coupling owing to the heavy Yb nucleus.

Spectroscopy of a tetrahedral doubly magic candidate nucleus <sup>160</sup><sub>70</sub>Yb<sub>90</sub>

The decay scheme of $^{160}$Yb nucleus populated in the $^{148}$Sm($^{16}$O, 4n)$^{160}$Yb reaction at 90 MeV has been studied. The gamma-coincidence data have been collected by using Indian National Gamma Array (INGA) composed of twenty Compton-suppressed Clover-Germanium detectors. Compared to the prior publications, the level scheme has been significantly modified owing to the observation of triple $\gamma$-coincidences and the measurements of $\gamma$ intensities, R$_{\theta}$ (asymmetry ratio), DCO (Directional Correlation of Oriented States) and IPDCO (Integrated Polarisation Directional Correlation of Oriented States) ratios.
 
 Theoretical results relevant for the exotic shape-coexistence related to the present context are presented and discussed. They illustrate the consequences of the fact that $^{160}$Yb is expected to be a doubly-magic (Z=70 and N=90) tetrahedral-symmetry nucleus as predicted by other authors. The historical criteria of identification of such a symmetry in nuclei are critically revisited in the context of the actual measurement and interpretation of its results and the precise new criteria are formulated employing recent results of the Fukuoka-Strasbourg collaboration.
 
 The experimental results are interpreted and discussed in detail. Limiting values of branching ratios for transitions observed by other authors but unseen in the present work are estimated. The population criteria of the $\beta$ and $\gamma$ vibration bands are revisited and discussed.
 
 Although no indication of the presence of the stable tetrahedral configuration has been obtained, arguments are given towards the possible presence of the $Y_{32}$ (`tetrahedral component') vibrations around the ground-state equilibrium. With the improvement of the spectroscopic information provided by the new data the way is opened for designed experiment(s) based on the unambiguous identification criteria of tetrahedral symmetry presented in this article.

Excited negative parity bands in 160Yb

Negative parity rotational bands in Yb nucleus have been studied. They were populated in the 148Sm(16O, 4n)160Yb reaction at 90 MeV. The gamma-coincidence data have been collected using Indian National Gamma Array composed of twenty Compton suppressed clover germanium (Ge) detectors. Double gating on triple gamma coincidence data were selectively used to develop the decay scheme for these negative parity bands by identifying and taking care of the multiplet transitions. The even- and odd-spin negative parity bands in 160Yb have been studied by comparing the reduced transition probability ratios with the similar bands in neighbouring even–even rare earth nuclei. It is concluded that the concerned odd-spin and even-spin bands are not signature partners and that their structures are compatible with those of the ‘pear-shape’ and ‘pyramid-shape’ oscillations, respectively, the octupole shapes superposed with the quadrupole shape of the ground-state.

Towards improved measurements of parity violation in atomic ytterbium

We report on progress towards performing precision measurements of parity violation in Yb, in which the theoretical prediction for a strong weak-interaction-induced effect in the 6s^{2} ^{1}S_{0} \rightarrow 5d6s ^{3}D_{1} optical transition at 408 nm has already been confirmed, with a measurement of the effect at the \approx 10 % level of accuracy. With a new atomic-beam apparatus offering enhanced sensitivity, we are aiming at precisely determining the parity violation observable in Yb, which will allow us to probe the distributions of neutrons in different isotopes, investigate physics beyond the Standard Model, as well as to study intra-nucleus weak interactions, through an observation of the anapole moment of Yb nuclei with nonzero spin. We present the experimental principle employed to probe atomic parity violation, describe our new apparatus, and discuss the attained experimental sensitivity as well as the methods for characterizing systematics in these measurements.

A fission model approach to alpha decay and cluster radioactivity of Dy, Er and Yb isotopes

Rare earth nuclei are probable candidates for exhibiting cluster radioactivity. In the present work, a theoretical study of alpha decay and heavy cluster emission from Dy, Er, and Yb nuclei in the mass range 150 < A < 190 has been carried out in a fission model approach. Some of the proton-rich isotopes of these nuclei are found to have long half-lives, but within the measurable range. Many of the neutron-rich isotopes under consideration are far from beta stability and the most probable light clusters predicted are highly exotic in nature and the corresponding half-lives are extremely short. However, the decays of most probable heavy clusters predicted have half-lives in the measurable range. The calculations on neutron-rich isotopes indicate the emergence of new magic numbers for protons and neutrons. The centrifugal barrier effect on decay rate of some proton-rich Er isotopes is also investigated.

Thermodynamic properties of hot nuclei within the self-consistent quasiparticle random-phase approximation

The thermodynamic properties of hot nuclei are described within the canonical and microcanonical ensemble approaches. These approaches are derived based on the solutions of the BCS and self-consistent quasiparticle random-phase approximation at zero temperature embedded into the canonical and microcanonical ensembles. The obtained results agree well with the recent data extracted from experimental level densities by Oslo group for $^{94}$Mo, $^{98}$Mo, $^{162}$Dy and $^{172}$Yb nuclei.

Electromagnetically&lt;?Pub Caret?&gt; induced transparency with nuclear spin

We report the observation of electromagnetically induced transparency in a sample of cryogenically cooled ground-state atomic ytterbium ((1)S(0)). The transparency is produced due to coherence between the optical field and the nuclear spin state of the (173)Yb nucleus. Because the nuclear spin states interact very weakly with their environment, they are resistant to decoherence due to inelastic collisions and inhomogenous fields. Consequently, atomic ensembles of pure nuclear spin states may be a superior medium for a variety of nonlinear optics and quantum information experiments.

Damping, motional narrowing, and chaos in rotational nuclei

We have studied the unresolved $\ensuremath{\gamma}$-ray spectrum of three ytterbium nuclei produced in heavy-ion fusion reactions and measured the two damping widths, ${\ensuremath{\Gamma}}_{\ensuremath{\mu}}$, the spreading (compound-damping) width, and ${\ensuremath{\Gamma}}_{\mathrm{rot}}$, the rotational damping width, together with ${P}_{\mathrm{nar}}$, the probability that the population enters and leaves a given state via the same component of the wave function. Our results for ${\ensuremath{\Gamma}}_{\ensuremath{\mu}}$ and ${\ensuremath{\Gamma}}_{\mathrm{rot}}$ are in good agreement with theoretical expectations, as well as with those of other groups using different methods. Our results for ${P}_{\mathrm{nar}}$ lead to a new method for quantitative evaluation of the full order-to-chaos transition in these Yb nuclei. Finally, we provide the first evidence for the motional narrowing of ${\ensuremath{\Gamma}}_{\mathrm{rot}}$ in nuclei. The basic physics occurring in this region is level mixing, which our simulation technique reproduces surprisingly well.

Order-to-chaos transition in rotational nuclei

We have developed a new method to study the order-to-chaos transition in rotational nuclei. Energy correlations between successive γ-rays are used to determine the average complexity of the levels and thereby the ratio of the interaction between levels to the level spacing. γ-Rays from fusion reactions, leading to 168,169,170Yb nuclei, were measured with Gammasphere, and the measured ratios span the range from nearly fully ordered to nearly fully chaotic.

Quadrupolar interactions in heavy fermion metal YbRh 2Si 2

We describe the g tensor experimentally revealed by Sichelschmidt et al. (Phys. Rev. Lett. 91 (2003) 156401), g ⊥ = 3.561 and g ∥ = 0.17 , at 5 K by means of crystal field interactions of the 4 f 13 configuration of the Yb 3 + ion of YbRh 2Si 2 in a slightly orthorhombically distorted tetragonal crystal field. We have shown that the temperature dependence of the quadrupolar interactions Q(T) of the Yb nucleus will help to distinguish between Γ 7 and Γ 6 ground state. For the Γ 7 ground state Q(T) is expected to exhibit an anomalous dependence.

Level densities andγ-ray strength functions inYb170,171,172

Level densities and radiative strength functions in $^{171}$Yb and $^{170}$Yb nuclei have been measured using the $^{171}$Yb($^3$He,$^3$He$^\prime\gamma$)$^{171}$Yb and $^{171}$Yb($^3$He,$\alpha\gamma$)$^{170}$Yb reactions. New data on $^{171}$Yb are compared to a previous measurement for $^{171}$Yb from the $^{172}$Yb($^3$He,$\alpha\gamma$)$^{171}$Yb reaction. Systematics of level densities and radiative strength functions in $^{170,171,172}$Yb are established. The entropy excess in $^{171}$Yb relative to the even-even nuclei $^{170,172}$Yb due to the unpaired neutron quasiparticle is found to be approximately 2$k_B$. Results for the radiative strength function from the two reactions lead to consistent parameters characterizing the ``pygmy'' resonances. Pygmy resonances in the $^{170,172}$Yb populated by the ($^3$He,$\alpha$) reaction appear to be split into two components for both of which a complete set of resonance parameters are obtained.

Optical spectroscopy ofYb2Ti2O7andY2Ti2O7:Yb3+and crystal-field parameters in rare-earth titanate pyrochlores

Optical absorption spectra of the ${\mathrm{Yb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ single crystals and luminescence spectra of the ${\mathrm{Y}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}:\mathrm{Yb}$ (1%) polycrystalline samples were registered at temperatures $4.2--300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. These spectra and earlier published data on magnetic properties of ${\mathrm{Yb}}^{3+}$ ions and on the temperature dependence of the electric field gradient at Yb nuclei in ${\mathrm{Yb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ were used to analyze the crystal-field parameters in rare-earth titanates with the pyrochlore structure. The self-consistent sets of crystal-field parameters for rare-earth ions in the $16d$ sites with the ${D}_{3d}$ symmetry that describe satisfactory all known single-ion magnetic properties and low-energy excitations in ${R}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ crystals ($R=\mathrm{Tb}$, Ho, Er, Tm, Yb) are presented.

Rotational damping in ytterbium nuclei.

We have made the first clear measurements of rotational damping widths in nuclei. In a mixture of three Yb nuclei, these widths are 300 +/- 60 keV between 1.2 and 1.5 MeV gamma-ray energy [approximately (37-57)Planck's constant]. Compound damping and motional narrowing are discussed in connection with these results.

Study of neutron-rich nuclei using deep-inelastic reactions

We have used the ${}^{48}{\mathrm{C}\mathrm{a}+}^{176}\mathrm{Yb}$ reaction to study the population of high-spin states in neutron-rich nuclei by deep-inelastic reactions. Using Gammasphere, we observed gamma transitions from nuclei several neutrons richer than the target. Yrast states with spin up to 20 were populated in this reaction. High-spin states in ${}^{175,177,178}\mathrm{Yb}$ were observed. In this region of reduced pairing, a reference based on experimental data was used to derive experimental Routhians. Systematics of experimental Routhians in neutron-rich Yb nuclei compare well with cranked shell-model calculations.

Microscopic simulations of gamma cascades in warm rotating nuclei.

The $\ensuremath{\gamma}$ decay of the excited rotating ${}^{168}$Yb nucleus has been simulated considering the competition between $E1$ and $E2$ transitions, using microscopically calculated rotational bands. The simulations were made for two different cases: (i) pure rotating mean field bands and (ii) rotational bands mixed by a residual interaction. Simulated $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ spectra were analyzed in the typical rotational ridge-valley region. The fluctuation analysis method, sensitive to the effective number of $\ensuremath{\gamma}$-decay paths, was also applied. An overall agreement between experimental and simulated data is found for the case of mixed rotational bands.

Statistical γ-ray multiplicity distributions in Dy and Yb nuclei

The statistical γ-ray multiplicity distributions following the reactions 163 Dy( 3He ,αx n) 162−x Dy and 173 Yb( 3He ,αx n) 172−x Yb have been studied. The mean value 〈 M〉 and standard deviation σ M have been extracted as functions of excitation energy. The method is based on the probability distribution of k-fold events, where an α-particle is observed in coincidence with signals in k γ-ray detectors. Techniques for isolating statistical γ-rays and subtracting random background, cross-talk and neutron contributions are discussed.

Angular distribution of photons from the delay of the GDR in hot and rotating light Yb nuclei from exclusive experiments

Angular distributions of photons associated with the damping of excited-state giant dipole resonances (GDR) in hot and rotating 161,162Yb nuclei have been measured in exclusive experiments using the HECTOR array. In reactions with heavy ions ( 48T) angular distributions are determined as a function of the angular momentum of the compound nuclei. In reactions with lighter ions ( 17,18O) a difference method is applied to isolate GDR decays originating from specific excitation regions. The systematics of the measured angular distributions as a function of excitation energy and angular momentum are compared to theories taking into account fluctuations of the shape and orientation of the excited nuclei.