High-spin Structure Research Articles

Detailed spectroscopy of Bi195

An experiment focused on the study of shape coexistence and new high-spin structures in $^{195}\mathrm{Bi}$ has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the $13/{2}^{+}$ isomeric state was extended up to ${I}^{\ensuremath{\pi}}=(49/{2}^{+})$ and an energy of 5706 keV. The ${I}^{\ensuremath{\pi}}=31/{2}^{+}$ member of the $\ensuremath{\pi}{i}_{13/2}$ band was also found to feed a new long-lived isomeric state with an excitation energy of 2616 keV and a spin and parity of ${I}^{\ensuremath{\pi}}=29/{2}^{+}$. The half-life of the $29/{2}^{+}$ isomeric state was determined to be $1.49(1)\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$. It decays via the emission of 457-keV $E2$ and 236-keV $E1$ transitions, respectively. A low-energy 46-keV $E2$ transition has been identified to depopulate the ($29/{2}^{\ensuremath{-}}$) isomeric state, with a measured half-life of ${T}_{1/2}=614(5)\phantom{\rule{0.28em}{0ex}}\mathrm{ns}$. This transition allows the excitation energy of the isomeric state to be determined as 2381 keV. The feeding patterns of both $29/{2}^{+}$ and ($29/{2}^{\ensuremath{-}}$) isomeric states have also been described. This is the first time collective structures have also been observed up to high spins and excitation energies in the neutron-deficient $^{195}\mathrm{Bi}$ nucleus. Evidence for the manifestation of shape coexistence in $^{195}\mathrm{Bi}$ is also discussed.

The impact of the intruder orbitals on the structure of neutron-rich Ag isotopes

The low-lying high-spin yrast band structure of neutron-rich 113,118–121Ag has been established for the first time using prompt γ-ray spectroscopy of isotopically identified fission fragments produced in the 9Be(238U, fγ) fusion- and transfer-induced fission processes. The newly obtained level energies follow the systematics of the neighboring isotopes. The sequences of levels exhibit an energy inheritance from states in the corresponding Cd core. A striking constancy of a large signature splitting in odd-A Ag throughout the long chain of isotopes with 50<N<82 and a signature inversion in even-A Ag isotopes, which are indications of triaxiality, were evidenced. These observed features were reproduced by large-scale shell-model calculations with a spherical basis for the first time in the Ag isotopic chain, revealing microscopically their complex nature with severely broken seniority ordering. The essential features of the observed signature splitting were further examined in the light of simplified, two-orbital shell-model calculations including only two intruder orbitals πg9/2 and νh11/2 from two consecutive shells above Z=50 and N=82 for protons and neutrons respectively, resulting in the πg9/2−3×νh11/2m configurations. The newly established bands were understood as fairly pure, built mainly on unique-parity intruder configurations and coupled to the basic states of the Cd core.

High spin structures in the A ≈ 40 mass region: from superdeformation to extreme deformation and clusterization (an example of 28Si)

The search for extremely deformed structures in the yrast and near-yrast region of 28Si has been performed within the cranked relativistic mean field theory up to spin I = 20ħ. The fingerprints of clusterization are seen (well pronounced) in the superdeformed (hyperdeformed) configurations.

Shape evolution with increasing angular momentum in the Ga66 nucleus

The high-spin nuclear structure of the odd-odd $^{66}\mathrm{Ga}$ nucleus was probed using heavy-ion induced fusion-evaporation reaction. The de-exciting $\ensuremath{\gamma}$ rays were detected by using the Indian National Gamma Array (INGA) consisting of high resolution Compton suppressed clover detectors. The level scheme of $^{66}\mathrm{Ga}$ was extended up to an excitation energy $({E}_{x})$ of $\ensuremath{\sim}10.6$ MeV with spin parity of ${21}^{(+)}$. Two new quadrupole bandlike structures, one positive and one negative parity, based on the states having spin parity of ${J}^{\ensuremath{\pi}}={11}^{+}$ and ${10}^{\ensuremath{-}}$, respectively, were found. The experimental energy levels are compared with calculations within the framework of shell model calculation using $jj44bpn$ effective interaction. The agreement between experiment and theory is good. The total Routhian surface calculations were performed to understand the shape of the $^{66}\mathrm{Ga}$ nucleus associated with the configurations $\ensuremath{\nu}({g}_{9/2}){}^{3}\phantom{\rule{0.16em}{0ex}}\ensuremath{\nu}({f}_{5/2}){}^{2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({g}_{9/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({f}_{5/2}){}^{2}$ and $\ensuremath{\nu}({g}_{9/2}){}^{2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\nu}({f}_{5/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({g}_{9/2}){}^{1}\phantom{\rule{0.16em}{0ex}}\ensuremath{\pi}({f}_{5/2}){}^{2}$ assigned to the positive and negative parity bands, respectively. In the frequency domain $\ensuremath{\omega}=0.20\text{--}0.30$ MeV, both the negative and positive parity quadrupole structures, favor prolate deformation whereas at $\ensuremath{\omega}=0.50$ MeV there is a sudden change to noncollective oblate shape in both the bands.

Nuclear Data Sheets for A=189

Evaluated experimental data are presented for 13 known mass 189 nuclides (Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po). Since the 2003Wu02 publication, structure and decay data from 25 new and primary publications have been incorporated in the current work, while adding a new 189Hf nuclide. New data have been added for all nuclides except 189Au and 189Hg. Moreover, several previous datasets were modified for β-decay Q values and conversion coefficients even when no new publications appeared since 2003Wu02.In spite of large amounts of data available for A=189 nuclides, several deficiencies remain, which are pointed out below in the hope that further experimental work may improve our knowledge of structure of these nuclides. For 189Hf and 189Ta, ground-state half-lives, and their decay schemes are unknown. An isomer in 189Ta has recently been established but its decay characteristics are unknown, even though several gamma rays were connected with its decay. No excited states are known in 189W and only one in 189Po. The decay scheme of 189W is known poorly with most gamma rays left as unassigned. The decay schemes of 189Au and 189Pb g.s. suffer from incompleteness, while those for the g.s. and isomer of 189Tl are almost absent. The decay schemes of g.s. and isomer of 189Hg are very complex as apparent from the study by 1996Wo04. Evaluators feel that these two decay schemes could be improved with modern gamma-ray detector arrays. While several isomers are known in many of the A=189 nuclides, there is in general lack of information of level half-lives, thus limiting the knowledge of transition probabilities. High-spin structures, including SD bands in 189Hg and 189Tl, are known in 189Re, 189Ir, 189Pt, 189Au, 189Hg, 189Tl, 189Pb and 189Bi. Single-particle transfer data are available for 189Re, 189Os, and 189Pt; and two-neutron transfer data for 189Ir.

Isomers and high-spin structures in the N=81 isotones Xe135 and Ba137

The high-spin structures of the N = 81 isotones 135Xe and 137Ba are investigated after multinucleontransfer (MNT) and fusion-evaporation reactions. Both nuclei are populated in (i) 136Xe+238U and (ii) 136Xe+208Pb MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii), in the 136Xe+198Pt MNT reaction employing the -ray array GAMMASPHERE in combination with the gas detector array Chico, and (iv) via a 11B+130Te fusion-evaporation reaction. The high-spin level schemes of 135Xe and 137Ba are considerably extended to higher energies. The 2058-keV (19=2 ) state in 135Xe is identified as an isomer, completing the systematics for the N = 81 isotones. Its half-life is measured to be 8.6(10) ns, corresponding to a transition probability of B(E2; 19=2 ! 15=2 ) = 0:539(69) W.u. Latest shell model calculations considering 132Sn as a closed core reproduce the experimental findings and provide guidance to the interpretation of the new levels. The experimentally deduced reduced quadrupole transition probabilities of the isomeric states are compared to shell-model predictions.

Coordination chemistry and bonding analysis of tetranuclear transition metal pyrene sandwich complexes

Geometry optimizations have been performed on the M4(Pyr)2 (M = Ti-Ni, Pd and Pt, Pyr = C16H10) complexes by means of DFT method using BP86 and mPW1PW91 functionals combined to the TZP basis set. The M4 moiety encapsulated between two pyrene ligands tends to establish M-L bonding with various hapticies from η2 to η6. In accordance with the coordination modes, the pyrene behaves as neutral, dianionic, or tetraanionic ligand. For the Ti, V, and Fe, the low-spin (S = 0) and the high-spin (S = 1) structures are isoenergetic, while the Cr, Mn, and Co structures prefer the high-spin states. The Ni, Pd, and Pt structures are more favorable in low-spin state. The zigzag metallic chain is predicted to be more stable than that of the two-dimensional sheet for the Pd complexes. The spin state changes of the studied complexes in their ground states could be characterized in some cases by different molecular structure modifications (structural isomerisation, where structural modifications accompany the spin state modification like as bonds and angles), electronic configurations (low-spin or high-spin), or oxidation states with respect to the metal charges, in agreement with the metal nature. The optimized structures obtained by both BP86 and mPW1PW91 methods are consistent to each other, where the energetic parameters follow similar tendencies regarding the stability order between isomers.

Systematical study of high-spin rotational bands in neutron-deficient Kr isotopes by the extended projected shell model

We analyze the high-spin structure of the even–even 72–80Kr isotopes using the Projected Shell Model (PSM). With the help of the Pfaffian formulas, we have vigorously extended the quasi-particle (qp) basis of the PSM code and applied in this mass region for the first time. We consider a sufficiently large multi-qp configuration space in order to describe high-spin rotational behavior. The results show that the calculation can reproduce most of the known rotational bands with positive- or negative-parity. Moreover, some side bands appearing in the near-yrast region are predicted. The main structure for each band is discussed in terms of multi-qp configurations. The variations in moment of inertia with spin are explained in terms of successive band crossings among the 2-qp, 4-qp, 6-qp, and 8-qp states. The B(E2) transition probabilities in these bands are also calculated. To further understand the high-spin behavior of these neutron-deficient nuclei and to confirm predictions of the present work, good high-spin data, especially for B(E2) transitions, are called for.

Nuclear Data Sheets for A = 70

Spectroscopic data for all nuclei with mass number A = 70 have been evaluated, and the corresponding level schemes from radioactive decay and reaction studies are presented. Since the previous evaluation, the half-life of 70Mn has been measured and excited states in 70Fe observed for the first time. Excited states in 70Ni have been more extensively studied while Coulomb excitation and collinear laser spectroscopy measurements in 70Cu have allowed for firm Jπ assignments. Despite new measurements, there remain some discrepancies in half-lives of low lying states in 70Zn. New measurements have extended the knowledge of high-spin band structures in 70Ge and 70As. This evaluation supersedes the prior A = 70 evaluation of 2004Tu09.

High-spin adducts of redox active 2,4,6,8-tetrakis(tert-butyl)phenoxazin-1-one with tetrahedral cobalt(II) complexes

The complex formation between redox active 2,4,6,8-tetrakis(tert-butyl)phenoxazin-1-one (L) and four-coordinate Co(II) complexes, resulting in six-coordinate adducts (I) (C77H82N12O5Co) and (II) (C38H41NO6F12Co) was studied. High-spin structure of the formed cobalt adducts I and II (hs-CoII–BQ) was established by X-ray diffraction analysis and magnetochemistry methods. Adducts I and II are stable over a wide temperature range (5–300 K) and are not involved in the redox process giving low-spin adducts (ls-CoIII–SQ) studied previously.

High-spin states in the semimagic nucleusY89and neutron-core excitations in theN=50isotones

The semimagic nucleus $^{89}\mathrm{Y}$ has been investigated using the $^{82}\mathrm{Se}(^{11}\mathrm{B},4n)$ reaction at beam energies of 48 and 52 MeV. More than 24 new transitions have been identified, leading to a considerable extension of the level structures of $^{89}\mathrm{Y}$. The experimental results are compared with the large-basis shell model calculations. They show that cross-shell neutron excitations play a pivotal role in high-spin level structures of $^{89}\mathrm{Y}$. The systematic features of neutron-core excitations in the $N=50$ isotones are also discussed.

Structures, Unimolecular Fragmentations, and Reactivities of the Self-Assembled Multimetallic/Peptide Complexes [Mnn (GlyGly-H)2n-1 ](+) and [Mnn+1 (GlyGly-H)2n ](2.).

Complexes of Mn(2+) with deprotonated GlyGly are investigated by sustained off-resonance irradiation collision-induced dissociation (SORI-CID), infrared multiple-photon dissociation spectroscopy, ion-molecule reactions, and computational methods. Singly [Mnn (GlyGly-H)2n-1 ](+) and doubly [Mnn+1 (GlyGly-H)2n ](2+) charged clusters are formed from aqueous solutions of MnCl2 and GlyGly by electrospray ionization. The most intense ion produced was the singly charged [M2 (GlyGly-H)3 ](+) cluster. Singly charged clusters show extensive fragmentations of small neutral molecules such as water and carbon dioxide as well as dissociation pathways related to the loss of NH2 CHCO and GlyGly. For the doubly charged clusters, however, loss of GlyGly is observed as the main dissociation pathway. Structure elucidation of [Mn3 (GlyGly-H)4 ](2+) clusters has also been done by IRMPD spectroscopy as well as DFT calculations. It is shown that the lowest energy structure of the [Mn3 (GlyGly-H)4 ](2+) cluster is deprotonated at all carboxylic acid groups and metal ions are coordinated with carbonyl oxygen atoms, and that all amine nitrogen atoms are hydrogen bonded to the amide hydrogen. A comparison of the calculated high-spin (sextet) and low-spin (quartet) state structures of [Mn3 (GlyGly-H)4 ](2+) is provided. IRMPD spectroscopic results are in agreement with the lowest energy high-spin structure computed. Also, the gas-phase reactivity of these complexes towards neutral CO and water was investigated. The parent complexes did not add any water or CO, presumably due to saturation at the metal cation. However, once some of the ligand was removed via CO2 laser IRMPD, water was seen to add to the complex. These results are consistent with high-spin Mn(2+) complexes.

High-spin structure ofXe134

Author(s): Vogt, A; Birkenbach, B; Reiter, P; Blazhev, A; Siciliano, M; Valiente-Dobon, JJ; Wheldon, C; Bazzacco, D; Bowry, M; Bracco, A; Bruyneel, B; Chakrawarthy, RS; Chapman, R; Cline, D; Corradi, L; Crespi, FCL; Cromaz, M; De Angelis, G; Eberth, J; Fallon, P; Farnea, E; Fioretto, E; Freeman, SJ; Gadea, A; Geibel, K; Gelletly, W; Gengelbach, A; Giaz, A; Gorgen, A; Gottardo, A; Hayes, AB; Hess, H; Hua, H; John, PR; Jolie, J; Jungclaus, A; Korten, W; Lee, IY; Leoni, S; Liang, X; Lunardi, S; Macchiavelli, AO; Menegazzo, R; Mengoni, D; Michelagnoli, C; Mijatovic, T; Montagnoli, G; Montanari, D; Napoli, D; Pearson, CJ; Pellegri, L; Podolyak, Z; Pollarolo, G; Pullia, A; Radeck, F; Recchia, F; Regan, PH; Sahin, E; Scarlassara, F; Sletten, G; Smith, JF; Soderstrom, PA; Stefanini, AM; Steinbach, T; Stezowski, O; Szilner, S; Szpak, B; Teng, R; Ur, C; Vandone, V; Ward, D; Warner, DD; Wiens, A; Wu, CY | Abstract: Detailed spectroscopic information on the N∼82 nuclei is necessary to benchmark shell-model calculations in the region. The nuclear structure above long-lived isomers in Xe134 is investigated after multinucleon transfer (MNT) and actinide fission. Xenon-134 was populated as (i) a transfer product in Xe136+U238 and Xe136+Pb208 MNT reactions and (ii) as a fission product in the Xe136+U238 reaction employing the high-resolution Advanced Gamma Tracking Array (AGATA). Trajectory reconstruction has been applied for the complete identification of beamlike transfer products with the magnetic spectrometer PRISMA. The Xe136+Pt198 MNT reaction was studied with the γ-ray spectrometer GAMMASPHERE in combination with the gas detector array Compact Heavy Ion Counter (CHICO). Several high-spin states in Xe134 on top of the two long-lived isomers are discovered based on γγ-coincidence relationships and information on the γ-ray angular distributions as well as excitation energies from the total kinetic energy loss and fission fragments. The revised level scheme of Xe134 is extended up to an excitation energy of 5.832 MeV with tentative spin-parity assignments up to 16+. Previous assignments of states above the 7- isomer are revised. Latest shell-model calculations employing two different effective interactions reproduce the experimental findings and support the new spin and parity assignments.

Particle-number conserving analysis of the high-spin structure of 159Ho

The high-spin rotational bands in odd-Z nuclei 159Ho (Z=67) are investigated using the cranked shell model with the pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency ħω are reproduced very well by the calculations. The splitting between the signature partners of the yrast band 7/2−[523] is discussed and the splitting of the excited band 7/2+[404] above ħω∼0.30 MeV is predicted due to the level crossing with 1/2+[411]. The calculated B(E2) transition probabilities are also suggested for future experiments.

Nuclear Data Sheets for A = 227

The evaluated spectroscopic data are presented for ten known nuclides of mass 227 (Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, Np). For 227Po, 227At, 227Rn, 227Pa, 227U and 227Np nuclei, only the ground-state information is available. Their decay characteristics are mostly unknown. Levels in 227Fr are known only from the decay of 227Rn to 227Fr. This decay scheme at present cannot be normalized to deduce γ intensities per 100 decays due to lack of knowledge about multipolarities of many low-energy transitions. The levels in 227Ra, 227Ac and 227Th are known from several decays and reactions, including particle-transfer data for 227Ra and 227Ac. The decay scheme of 227Ra to 227Ac was last studied in 1971 using small Ge detectors. Improved γ-ray intensity data need to be obtained with a better γ-detection system. The datasets for 227Ac have undergone extensive revisions, including detailed data for 231Pa α decay from 1986BaYK report, and single-proton transfer data from 1986MaYU thesis. High-spin (J>13/2 or so) structures are known only for 227Th. Level lifetime data are quite scarce for all the nuclides in this mass chain, thus limiting the knowledge of reduced transition probabilities.Band structures for 227Fr, 227Ra, 227Ac and 227Th are known in detail, together with evidence of weak octupole deformation and consequent parity-doublet structures.This evaluation was carried out as part of a joint IAEA-ICTP workshop for Nuclear Structure and Decay Data, organized and hosted by the IAEA, Vienna and ICTP, Trieste, March 24–28, 2014. The evaluation work was coordinated by B. Singh (McMaster). This work supersedes previous A=227 evaluation (2001Br31) published by E. Browne which covered literature before May 2001.

Isomers and oblate collectivity at high spin in neutron-rich Pt isotopes

Isomers and high-spin structures with rotation-aligned oblate configurations have been studied in several Pt isotopes. The 12 + states in the even Pt isotopes from 192–198 Pt are found to be metastable, and have ( i 13/2 ) 2 neutron character. The progression of E 2 transition probabilities from the 12 + to 10 + states across the Pt isotopic chain implies reduction in collectivity, followed by an abrupt decrease at N =120 ( 198 Pt). This behavior is quite distinct from the gradual decrease of B ( E 2) values near the respective ground states. A large contribution from aligned angular momentum, to the rotational sequences built on the 12 + states, is visible. This is due to the relatively small crossing frequencies for nucleons in low-Ω orbitals at oblate deformation in comparison to higher values for prolate shapes. As a result, oblate rotation is found to be increasingly favored for higher neutron numbers.

Quantum chemical modeling of pyrene-4,5-dione adducts with cobalt diketonates

DFT computational modeling (B3LYP∗/6-311++G(d,p)) of a series of adducts of CoIIbis-(malonate), bis-(acetylacetonate), bis-(hexafluoroacetylacetonate) and bis-(trifluoroacetylacetonate) with pyrene-4,5-dione has been performed. The results of calculations of CoIIbis-(malonate) complex point to the possibility of the occurrence of valence tautomeric (VT) rearrangements of this compound. It has been shown that methyl groups into the diketonate moiety (CoIIbis-(acetylacetonate) adduct) destabilize the high-spin state structure giving rise to the competitive process of dissociation into the initial bis-chelate complex and redox-active ligand. An adduct of CoIIbis-(hexafluoroacetylacetonate) with pyrene-4,5-dione is energy preferred to the high-spin state electromer, which obstructs the VT process. The most suitable energy parameters for the occurrence of thermally initiated valence tautomeric transformation (stability of the adduct with respect to dissociation into the components, energy preference of the low-spin electronic state and thermally achievable energy barrier to intramolecular electron transfer determining the intrinsic mechanism of VT rearrangements) are found for the adduct of pyrene-4,5-dione with CoIIbis-(trifluoroacetylacetonate).

High-spin Structures of the Near-spherical Nuclei $^{91,92}$Zr

In the present work, we have interpreted recently available experimental data for high-spin states of the near-spherical nuclei $^{91,92}$Zr, using the shell-model calculations within the full $f_{5/2}$, $p_{3/2}$, $p_{1/2}$, $g_{9/2}$ model space for protons and valence neutrons in $g_{9/2}$, $g_{7/2}$, $d_{5/2}$ orbits. We have employed a truncation for the neutrons due to huge matrix dimensions, by allowing one neutron excitation from $g_{9/2}$ orbital to $d_{5/2}$ and $g_{7/2}$ orbitals. Results are in good agreement with the available experimental data. Thus, theoretically, we have identified the structure of many high-spin states, which were tentatively assigned in the recent experimental work. The $^{91}$Zr $21/2^+$ isomer lies at low-energy region due to fully aligned spins of two $g_{9/2}$ protons and one $d_{5/2}$ neutron.

Analysis of proton and neutron pair breakings: High-spin structures of 124–127Te isotopes

In the present work recently available experimental data for high-spin states of four nuclei, Te52124, Te52125, Te52126, and Te52127, have been interpreted using state-of-the-art shell model calculations. The calculations have been performed in the 50–82 valence shell composed of 1g7/2, 2d5/2, 1h11/2, 3s1/2, and 2d3/2 orbitals. We have compared our results with the available experimental data for excitation energies and transition probabilities, including high-spin states. The results are in reasonable agreement with the available experimental data. The wave functions, particularly, the specific proton and neutron configurations which are involved to generate the angular momentum along the yrast lines are discussed. We have also estimated overall contribution of three-body forces in the energy level shifting. Finally, results with modified effective interaction are also reported.

High-spin structure of 80Kr

High-spin structure of 80Kr