High-spin Structure Research Articles

High-Spin States in the N = 50 Nucleus 88Sr

The excited states of 88Sr have been produced in the reaction16O(82Se,4p6n) and studied using in-beam γ spectroscopytechniques. Two high-spin level structures have been observed andestablished up to 8.5 MeV and 7.9 MeV excitation energy, respectively. Basedon the measurements of the directional correlations of γ-raysde-exciting oriented states and anisotropic factors of γ-rays, spinvalues of the excited states have been assigned up to the highest levelsobserved.

High-spin structure and electromagnetic transition strengths in104Cd

The recoil distance Doppler shift and Doppler shift attenuation techniques were employed to determine for the first time lifetimes of high spin states in Cd-104in the time range 0.3 ps less than equal to tau less than 1.2 ns. The new experimental results are discussed in the frame of the interacting boson plus broken pair model.

Identification of excited states in 167Os and 168Os: shape coexistence at extreme neutron deficiency

Excited states in the very neutron-deficient isotopes 167Os and 168Os have been observed using the reaction 112Sn( 58Ni, 2p xn). The jurosphere γ-ray spectrometer array was used in conjunction with the ritu gas-filled recoil separator to collect prompt γ radiation in coincidence with recoils implanted in a silicon strip detector located at the focal plane of ritu. Using a selective recoil decay tagging technique it has been possible to unambiguously assign γ-ray transitions to 167Os and 168Os through the characteristic α radioactivity of these nuclides. The high-spin structure of the bands is discussed in terms of quasiparticle configurations within the framework of the cranked shell model. The role of shape coexistence in 168Os is examined with phenomenological three-band mixing calculations.

Oxidation state dependence of the geometry, electronic structure, and magnetic coupling in mixed oxo- and carboxylato-bridged manganese dimers.

Approximate density functional theory has been used to investigate changes in the geometry and electronic structure of the mixed oxo- and carboxylato-bridged dimers [Mn(2)(mu-O)(2)(O(2)CH)(NH(3))(6)](n+)and [Mn(2)(mu-O)(O(2)CH)(2)(NH(3))(6)](n+)in the Mn(IV)Mn(IV), Mn(III)Mn(IV), and Mn(III)Mn(III) oxidation states. The magnetic coupling in the dimer is profoundly affected by changes in both the bridging ligands and Mn oxidation state. In particular, change in the bridging structure has a dramatic effect on the nature of the Jahn-Teller distortion observed for the Mn(III) centers in the III/III and III/IV dimers. The principal magnetic interactions in [Mn(2)(mu-O)(2)(O(2)CH)(NH(3))(6)](n+)() involve the J(xz/xz)and J(yz/yz) pathways but due to the tilt of the Mn(2)O(2) core, they are less efficient than in the planar di-mu-oxo structure and, consequently, the calculated exchange coupling constants are generally smaller. In both the III/III and III/IV dimers, the Mn(III) centers are high-spin, and the Jahn-Teller effect gives rise to axially elongated Mn(III) geometries with the distortion axis along the Mn-O(c) bonds. In the III/IV dimer, the tilt of the Mn(2)O(2) core enhances the crossed exchange J(x)()()2(-)(y)()()2(/)(z)()()2 pathway relative to the planar di-mu-oxo counterpart, leading to significant delocalization of the odd electron. Since this delocalization pathway partially converts the Mn(IV) ion into low-spin Mn(III), the magnetic exchange in the ground state can be considered to arise from two interacting spin ladders, one is the result of coupling between Mn(IV) (S = 3/2) and high-spin Mn(III) (S = 2), the other is the result of coupling between Mn(IV) (S = 3/2) and low-spin Mn(III) (S = 1). In [Mn(2)(mu-O)(O(2)CH)(2)(NH(3))(6)](n+)(), both the III/III dimer and the lowest energy structure for the III/IV dimer involve high-spin Mn(III), but the Jahn-Teller axis is now orientated along the Mn-oxo bond, giving rise to axially compressed Mn(III) geometries with long Mn-O(c) equatorial bonds. In the IV/IV dimer, the ferromagnetic crossed exchange J(yz)()(/)(z)()()2 pathway partially cancels J(yz/yz) and, as a consequence, the antiferromagnetic J(xz/xz) pathway dominates the magnetic coupling. In the III/III dimer, the J(yz/yz) pathway is minimized due to the smaller Mn-O-Mn angle, and since the ferromagnetic J(yz)()(/)(z)()()2 pathway largely negates J(xz/xz), relatively weak overall antiferromagnetic coupling results. In the III/IV dimer, the structures involving high-spin and low-spin Mn(III) are almost degenerate. In the high-spin case, the odd electron is localized on the Mn(III) center, and the resulting antiferromagnetic coupling is similar to that found for the IV/IV dimer. In the alternative low-spin structure, the odd electron is significantly delocalized due to the crossed J(yz)()(/)(z)()()2 pathway, and cancellation between ferromagnetic and antiferromagnetic pathways leads to overall weak magnetic coupling. The delocalization partially converts the Mn(IV) ion into high-spin Mn(III), and consequently, the spin ladders arising from coupling of Mn(IV) (S = 3/2) with high-spin (S = 2) and low-spin (S = 1) Mn(III) are configurationally mixed. Thus, in principle, the ground-state magnetic coupling in the mixed-valence dimer will involve contributions from three spin-ladders, two associated with the delocalized low-spin structure and the third arising from the localized high-spin structure.

Spectroscopy of 112Pd using heavy-ion-induced fission

High-spin states in 112Pd were studied using prompt γ-ray spectroscopy with Gammasphere following heavy-ion-induced fission in the reaction 18O + 208Pb at 91 MeV. A new 8+ level at 2638 keV was discovered with transitions connecting it to the yrast band and the quasi-gamma band. The three, now established, closely spaced 8+ states indicate a mixing between the ground-state band, s-band, and quasi-gamma band. Several high-spin structures with likely negative parity have been extended to higher spin and it is proposed that they are based on the νh11/2(g7/2d5/2) and νh11/2(s1/2d3/2) configurations.

Rotational bands near 56Ni

Rotational bands have been found in Co-57 and Ni-57, using Gammasphere in conjunction with the Microball and 30 neutron detectors. The bands in Co-57, extending the mass 60 region of deformation down to Z = 27, are signature partner sequences. The quadrupole moments and dynamic moments of inertia of the new bands in both nuclei are similar to those of rotational sequences in the neighboring nuclei. The high-spin structure of Co-57 is compared with Skyrme Hartree-Fock calculations.

High-spin multiparticle-hole excitations in 148Eu

Studies by means of 155 MeV 27Al bombardment on a 130Te target revealed in 148Eu high-spin structures up to spin 31?, in addition to a cascade extended to the 11088.1 keV excitation. The observed levels are tentatively assigned as complex multiparticle-hole proton and neutron configurations.

High-spin structures and alignment properties in 126Ce

High-spin structures and alignment properties in 126Ce

High-Spin Structures of the Odd-A 97 - 105 43 Tc Isotopes

The 99−105Tc isotopes have been produced at high spin as fission fragments following the fusion reaction 37Cl(170 MeV) + 176Yb and studied with the Euroball3 array. The high-spin structures of 103Tc have been identified for the first time. From the systematics of the yrast states of 97−105Tc, the location of individual proton states can be analyzed as a function of the neutron number.

Heme structure of hemoglobin M Iwate [alpha 87(F8)His-->Tyr]: a UV and visible resonance Raman study.

Heme structures of a natural mutant hemoglobin (Hb), Hb M Iwate [alpha87(F8)His-->Tyr], and protonation of its F8-Tyr were examined with the 244-nm excited UV resonance Raman (UVRR) and the 406.7- and 441.6-nm excited visible resonance Raman (RR) spectroscopy. It was clarified from the UVRR bands at 1605 and 1166 cm(-)(1) characteristic of tyrosinate that the tyrosine (F8) of the abnormal subunit in Hb M Iwate adopts a deprotonated form. UV Raman bands of other Tyr residues indicated that the protein takes the T-quaternary structure even in the met form. Although both hemes of alpha and beta subunits in metHb A take a six-coordinate (6c) high-spin structure, the 406.7-nm excited RR spectrum of metHb M Iwate indicated that the abnormal alpha subunit adopts a 5c high-spin structure. The present results and our previous observation of the nu(Fe)(-)(O(tyrosine)) Raman band [Nagai et al. (1989) Biochemistry 28, 2418-2422] have proved that F8-tyrosinate is covalently bound to Fe(III) heme in the alpha subunit of Hb M Iwate. As a result, peripheral groups of porphyrin ring, especially the vinyl and the propionate side chains, were so strongly influenced that the RR spectrum in the low-frequency region excited at 406.7 nm is distinctly changed from the normal pattern. When Hb M Iwate was fully reduced, the characteristic UVRR bands of tyrosinate disappeared and the Raman bands of tyrosine at 1620 (Y8a), 1207 (Y7a), and 1177 cm(-)(1) (Y9a) increased in intensity. Coordination of distal His(E7) to the Fe(II) heme in the reduced alpha subunit of Hb M Iwate was proved by the observation of the nu(Fe)(-)(His) RR band in the 441.6-nm excited RR spectrum at the same frequency as that of its isolated alpha chain. The effects of the distal-His coordination on the heme appeared as a distortion of the peripheral groups of heme. A possible mechanism for the formation of a Fe(III)-tyrosinate bond in Hb M Iwate is discussed.

Smooth band termination in odd mass La nuclei:127,129,131La

High spin states in 127,129,131La have been investigated using the 100Mo(32S,p4n), E=160 MeV, 100Mo(34S,p4n), E=155 MeV, and 100Mo(36S,p4n), E=160 MeV reactions, respectively. γ rays were detected using the EUROBALL IV (127,131La) and EUROGAM II (129La) arrays. The results have enabled the negative parity yrast band, built on the πh11/2 orbital at low spin, and the lowest lying (π,α)=(+,±12) bands to be extended to higher spins. The positive parity, α=−12, bands in 127,129La and the positive parity, α=12, band in 127La can be interpreted, with the aid of cranked Nilsson-Strutinsky calculations, as examples of smoothly terminating bands in valence space based on both signatures of the π[(g7/2d5/2)5(h11/2)2]⊗ν[(g7/2d5/2)x(h11/2)6(d3/2s1/2)2] configuration, where x=12,14 for 127,129La, respectively. The favored α=−12 bands of these configurations are predicted to terminate at 952+ and 832+, respectively, and experimentally the bands are observed to within two transitions of these terminating states. The data for the positive parity, α=12, band in 129La do not allow any firm conclusions to be made regarding the high spin structure of this band. The positive parity bands in 131La have a different structure at high spin compared with the lighter nuclei. In this case the bands may be interpreted in terms of a π[(g7/2d5/2)5(h11/2)2]⊗ν[(g7/2d5/2)12(h11/2)8(d3/2s1/2)4] configuration relative to a 100Sn core.Received 14 April 2000DOI:https://doi.org/10.1103/PhysRevC.62.034315©2000 American Physical Society

High-spin structure of the neutron-rich 44 104,106,108 Ru isotopes: γ-vibrational bands and two-quasiparticle excitations

The 104,106,108Ru nuclei have been produced as fission fragments following the fusion reaction 28Si + 176Yb at 145 MeV bombarding energy; prompt gamma rays emitted in the reaction were detected using the Eurogam II array. Their high-spin level schemes have been obtained, particularly several side bands have been extended or newly observed. Experimental results are discussed in the framework of both collective model and the rotating mean-field approach in which the Gogny force is the sole input. These calculations provide very good descriptions of both low-spin and high-spin structures observed in the neutron-rich even-A Ru isotopes.

High-spin yrast structure of 32S suggested by symmetry-unrestricted, cranked Hartree–Fock calculations

The high-spin yrast structure of 32S is investigated by means of the cranked Skyrme–Hartree–Fock method in the three-dimensional Cartesian-mesh representation without imposing restrictions on spatial symmetries. The result suggests that (1) a crossover from the superdeformed to the hyperdeformed-like configurations takes place on the yrast line at angular momentum I≃24, which corresponds to the “band termination” point in the cranked harmonic-oscillator model, and (2) non-axial octupole deformations of the Y 31 type play an important role in the yrast states in the range 5≤I≤13.

Rotational and multi-quasiparticle excitations in [formula omitted]Re

The high-spin structure of the nucleus 183 Re has been studied following the 176 Yb( 11 B,4n) reaction. High- K, multi-quasiparticle excitations compete with collective rotation in the formation of the yrast and near-yrast structures. Broken-pair (i 13/2) 2 excitations ( t-bands) play a dominant role, generating considerable angular momentum both along and perpendicular to the prolate symmetry axis. The stability of axially symmetric, prolate shapes is explored through comparisons with potential-energy-surface calculations. The possible onset of oblate rotation at high angular momentum is discussed.

New insight in the level structure of 153Er

The high-spin level structure of the 153Er nucleus has been reinvestigated by in-beam γ-ray and electron spectroscopy with (14N,pxn) reaction. Excitation energies, spin and parity assignments are unambiguously established for the two lowest isomers T1/2≃ 380 ns and T1/2\simeq 10 ns. The characteristics of the third one (T1/2≃ 250 ns) at 5.2 MeV are still questionable but its main decay modes are better known. An extension of the level scheme is proposed up to 8.4 MeV.Experimental results have been discussed in terms of shell model multiplets and compared with the other structures observed in N=85 neighbouring nuclei.

Analyzing powers in inclusive pion production at high energy and nucleon spin structure

Analyzing powers in inclusive pion production at high energy and nucleon spin structure

High-spin collective structures in 178Pt

High-spin collective structures in 178Pt

High-spin structure of the 113–116Cd isotopes produced by heavy-ion induced fission reaction

High-spin states in 113–116Cd have been investigated with the heavy-ion induced fission reaction 28Si + 176Yb at 165 MeV. The experiment was performed with the Eurogam II array. New rotational bands based on two quasi-particle states have been observed for even-even cadmium isotopes. A new level scheme based on the 11/2– isomeric state is proposed for 115Cd and the one of 113Cd has been extended to spin (31/2–). Hartree–Fock calculations for even-even isotopes show a prolate deformation in this mass region. The decoupled bands identified in both odd nuclei are interpreted as being built upon a low-Ω11/2 quasi-neutron configuration.

Identification of levels in neutron-rich145Ceand147Cenuclei

High-spin structures in the neutron-rich nuclei ${}^{145}\mathrm{Ce}$ and ${}^{147}\mathrm{Ce}$ produced in the spontaneous fission of ${}^{252}\mathrm{Cf}$ have been investigated by prompt $\ensuremath{\gamma}$-ray spectroscopy. A collective band structure in ${}^{145}\mathrm{Ce}$ is identified. Several sidebands along with the new high-spin states in ${}^{147}\mathrm{Ce}$ are also identified. Particle-plus-rotor model calculations indicate that the yrast bands in ${}^{145}\mathrm{Ce}$ and ${}^{147}\mathrm{Ce}$ most probably originate from coupling of the $\ensuremath{\nu}{i}_{13/2}$ orbital to the ground states of ${}^{144}\mathrm{Ce}$ and ${}^{146}\mathrm{Ce}.$ The ground state configurations of ${}^{145,147}\mathrm{Ce}$ are $(\ensuremath{\nu}{h}_{9/2}+\ensuremath{\nu}{f}_{7/2})$ and $\ensuremath{\nu}{h}_{9/2},$ respectively.

Low-lying levels and high-spin band structures in 102Rh

Levels in 102Rh have been populated in the reaction 70Zn+ 36S at 130 MeV. The level structure of 102Rh has been investigated using the EUROGAM II array. Low-lying states and four high-spin bands have been identified. The configurations of low-lying levels and two-quasiparticle bands are interpreted in the frame of the interacting boson-fermion-fermion model. The four observed band structures are also compared with cranked shell model calculations using a modified oscillator potential.