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Two nearly degenerate positive-parity bands with the πg9/22⊗νg9/2−1 configuration and three nearly degenerate negative-parity bands with the πg9/2(p3/2,f5/2)⊗νg9/2−1 configuration have been identified in $^{81}$Kr. They are interpreted as chiral doublet bands and pseudospin-chiral triplet bands, which is supported by the constrained covariant density functional theory and the multiparticle plus rotor model calculations. The present work reports two new chiral configurations πg9/22⊗νg9/2−1 and πg9/2(p3/2,f5/2)⊗νg9/2−1, and the first example of pseudospin-chiral triplet bands involving the π(p3/2,f5/2) pseudospin doublet.

The level structure of I124 (Z=53, N=71) has been studied via the Sn122(Li7,5n)I124 reaction with a beam energy of 54 MeV. Through in-beam and out-of-beam ?-ray spectroscopy, the sophisticated low-lying levels including isomeric states and numerous collective states have been established for the first time. A positive-parity collective band built on the 10+ state at 1297 keV is interpreted as being associated with the combination of a proton and a neutron in the same intruder h11/2 orbital, namely the ph11/2?h11/2 configuration. This band shows a typical quadrupole vibrational character. In contrast, the negative parity bands based on the pg7/2?h11/2 configuration show a soft triaxial rotation. An isomeric 8- state at 689 keV with a half-life of 14 ns can be explained as a K isomer due to a proton with an ?p=9/2 in the g9/2 orbital coupled to a neutron with an ?n=7/2 in the h11/2 orbital. The excited states based on this pg9/2?h11/2 configuration show a coupled rotational structure. Another coupled rotational band built on the 6+ state at 714 keV is thought to be based on the pg9/2?d3/2 configuration.

We report for the first time two distinctive features in the odd–odd nucleus 120I: a pair of doublet bands and a high-spin isomer built on the π h 11 / 2 ν h 11 / 2 configuration. For producing the excited states of 120I, a fusion-evaporation reaction 118Sn(6Li, 4n) at E = l a b 48 MeV was employed. The beam was provided by the 14UD tandem accelerator of the Heavy Ion Accelerator Facility at the Australian National University. The observed doublet structure built on the positive-parity states is the first case and unique in isotopes with Z = 53 . The emerging properties are indicative of the known chiral characteristics, leading to a doubling of states for the π h 11 / 2 ν h 11 / 2 configuration. In contrast, the high-spin isomer with a half-life of 49(2) ns at spin-parity J π = 25 + can be explained in terms of a noncollective oblate structure with the full alignment of six valence nucleons outside the 114Sn core: three protons ( g 7 / 2 ) 1 ( d 5 / 2 ) 1 ( h 11 / 2 ) 1 and three neutrons ( h 11 / 2 ) 3 . This is an outstanding case that reveals a pure single-particle structure consisting of equal numbers of valence protons and neutrons outside the semi-double shell closure of 114Sn with Z = 50 and N = 64 .

The level structure of the odd-odd iodine nucleus I122 has been studied by the Sn120 (Li7, 5n)I122 reaction at Elab=58 MeV. Two chopped beams from the 14UD (Unit Doubled) tandem heavy-ion accelerator at the Australian National University were used; one was a nanosecond (ns) pulsed-beam with separation of 1.7 microseconds (μs) and the second one was a 60-μs beam separated by 880μs. Through in-beam and out-of-beam γ-ray spectroscopy, the complex proton-neutron multiplet states, including isomers with half-lives of a few tens of ns to a few tens of μs, have been identified. Collective states based on the proton h11/2 orbital exhibit two kinds of structure depending upon the coupled neutron orbital: a quadrupole vibration when involving the h11/2 orbital and a γ-soft deformed rotation when involving the g7/2 orbital. With spherical shell model and deformed shell-model calculations, the observed level structures are explained.

ispartof: ACTA PHYSICA POLONICA B vol:51 issue:3 pages:799-806 ispartof: location:POLAND, Piaski status: published

A pair of rotational bands associated with the pi h(9/2) circle times nu i(13/2)(-1) configuration at lower spins and with the pi h(9/2) circle times nu i(13/2)(-3) configuration at higher spins is found in Tl-194. The two 4-quasiparticle bands show exceptionally close near-degeneracy in the excitation energies. Furthermore close similarity is also found in their alignments and B(M1)/B(E2) reduced transition probability ratios. Such close near-degeneracy probably indicates chiral geometry in the angular momentum space. (c) 2013 Elsevier B.V. All rights reserved.

Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive- and negative-parity bands have been identified in ^{78}Br. They are interpreted as multiple chiral doublet bands with octupole correlations, which is supported by the microscopic multidimensionally-constrained covariant density functional theory and triaxial particle rotor model calculations. This observation reports the first example of chiral geometry in octupole soft nuclei.

We have used the AFRODITE γ-ray spectrometer to measure yrare structures in 152,154,155Gd using (α,xn) reactions. The measurements on 152,154Gd have shown that there is no convincing evidence that the lowest excited 0 2 + states are β-vibrations based on the 0 1 + ground state. Rather these levels may be regarded as a “second vacuum” each with its own γ and octupole vibrations. This is confirmed by the blocking of the coupling of this core 0 2 + state in 154Gd to the [ 505 ] 11 / 2 − single-particle quasi-neutron orbital in 155Gd. The coupling of this orbital to the 2 + γ-vibration is observed since this coupling is not Pauli-blocked.

The low-lying, odd-spin negative parity bands in the mass 160 region have been identified as candidates for the rotation of a tetrahedral shape, as they have very weak in-band E2 transitions. We report the observation of such bands in 160 Yb and 154 Gd. They are crossed by 2 quasiparticle bands which allow band mixing calculations to be carried out to derive relative quadrupole moments. However, those studied are not consistent with zero, as required for tetrahedral shape. The aligned angular momenta of the bands suggest an octupole vibrational assignment.

The quantitative analysis of thin layers using Heavy Ion–Elastic Recoil Detection (HI–ERD) can be reliably performed if the stopping powers of the probing ions and recoils in a given target matrix are known accurately. Unfortunately for many projectile/target combinations experimental data is limited and where available, deviations of up to 50% between experiment and theory have been reported. This presentation describes the assembly of a Time of Flight–Energy (ToF–E) detector system developed for HI–ERD analysis and adapted for stopping power measurements at iThemba LABS. First results from energy loss measurements of 0.1–0.5 MeV/nucleon 28Si and 84Kr ions in ZrO2 are presented and compared with predictions of the widely used SRIM2003 (Stopping Range of Ions in Matter).

The first 2+ states in 134Ce and 136Nd and the second 2+ state in 136Nd were populated by Coulomb excitation at relativistic energies, and γ-rays were measured using the RISING setup at GSI. For 134Ce an indication of the excitation to the second 2+ state was observed. This experiment performed for the first time Coulomb excitation to second 2+ states with rare isotope beams at relativistic energies. For 136Nd the B ( E 2 ; 2 1 + → 0 + ) , B ( E 2 ; 2 2 + → 0 + ) , and B ( E 2 ; 2 2 + → 2 1 + ) values relative to the previously known B ( E 2 ; 2 1 + → 0 + ) value for 134Ce are determined as 81(10), 11(3) and 180(92) W.u., respectively. The results are discussed in the framework of geometrical models that indicate pronounced γ-softness in these nuclei.

New data have been obtained for 185Os following the 176Yb(13C,4n)185Os reaction, extendingthe pseudo-Nilsson $\frac{1}{2}^{-},\frac{3}{2}^{-}[\mathaccent126{4}\mathaccent126{1}\mathaccent126{1}]$ doublet structure and the $\frac{7}{2}^{-}[\mathaccent126{4}\mathaccent126{0}\mathaccent126{4}]$ band to significantly higher spins. Gamma-ray branching ratio data have been analysed to obtain extensive B(M1) and B(E2) ratios for intraband and interband transitions. The data are compared with particle-rotor calculations based on the pseudo-Nilsson potential and the Woods-Saxon potential. The results indicate that the pseudo-Nilsson approximation provides a good description of the $\frac{1}{2}^{-}$ , $\frac{3}{2}^{-}[\mathaccent126{4}\mathaccent126{1}\mathaccent126{1}]$ bands up to the first band crossing;the difference in magnitude between the model predictions and data for the $\frac{7}{2}^{-}[\mathaccent126{4}\mathaccent126{0}\mathaccent126{4}]$ band may be attributed to a lower deformation for the higher-K structure.

A study of the relative intensity of K-shell X-ray nuclear satellites as a function of atomic number, Z is presented. These satellites, which are generated during bombardment with high energetic protons of 66 MeV from targets composed of pure fluoride compounds for the rare earths and heavier metals including the platinum (Pt, Au) and fissionable metals (Th, U) are of particular interest in the quantitative elemental analysis of rare earth and heavy metals by energetic protons. This paper will describe aspects that may account for the production cross section of nuclear satellites for atomic numbers 57 ⩽ Z ⩽ 92. Previous results that showed a linear relationship between relative intensities and atomic number will be discussed.

The average g factors of high-spin states in 180,182,184 Pt were measured by the transient-field technique. In all three isotopes the quasicontinuum g factor at an angular momentum of ∼20ℏ is 〈 g 〉∼0.37. This contrasts with similar measurements on other nuclei that have 70⩽ Z ⩽80, where typical values of 〈 g 〉∼0.22 have been attributed to the influence of quasineutron alignments. Evidently proton and neutron configurations are about equally important at high spin in the Pt isotopes near mid-shell. This inference is consistent with the discrete spectroscopy, including the contention, supported by g K − g R values, that h 9/2 proton pairs align along with the i 13/2 neutrons at rotational frequencies of ℏ ω ≈0.3 MeV in 184 Pt. Links between the quasicontinuum g factors and features in the discrete spectroscopy are explored by comparing and contrasting the behavior of 184 Pt and 166 Hf.

CITATION: Ndayishimye, J. et al. 2017. Chiral Bands in 193TI. Acta Physica Polonica B, 48(3):343-346, doi:10.5506/APhysPolB.48.343.

The nature of the chiral candidate bands in $^{106}\mathrm{Ag}$, one of only two known examples of candidates which actually cross, is investigated experimentally and theoretically. Lifetimes have been determined for these bands in $^{106}\mathrm{Ag}$ using the Doppler-shift attenuation method with the $\ensuremath{\gamma}$-detector array AFRODITE. The level scheme of $^{106}\mathrm{Ag}$ has been extended, and three negative-parity bands have been observed to high spins. Configurations were assigned to the negative-parity bands based on a quasiparticle alignment analysis and on configuration-fixed constrained relativistic mean field calculations. The excitation energies, $B(M1)$ and $B(E2)$ values, as well as $B(M1)/B(E2)$ ratios have been compared with results of particle-rotor model calculations. From the investigations, it is concluded that the three close-lying negative-parity bands are a two-quasiparticle high-$K$ band and a pair of four-quasiparticle bands. The proposal that the two lowest-lying bands are chiral partners has not been confirmed.

165 Tm has been studied through the reactions 150 Nd( 19 F, 4n), E beam =85 MeV and 154 Sm ( 15 N, 4n), E beam =70 MeV. The level scheme has been extended to spin 71/2 − ℏ, and four new bands have been added. Two are assigned to the K =17/2, three-quasiparticle configurations, π [523]7/2 − ⊗ ν [642]5/2 + ⊗ ν [523]5/2 − and π [404]7/2 + ⊗ ν [642]5/2 + ⊗ ν [523]5/2 − , and the remaining two are assigned to γ -vibrations coupled to an h 9/2 proton. Lifetimes of high-spin states in the [541]1/2 − and [411]1/2 + bands have been measured using DSAM techniques, allowing transition quadrupole moments to be deduced. Furthermore, crossings between the [541]1/2 − and [523]7/2 − bands and between the [411]1/2 + and [404]7/2 + bands are analysed with a band-mixing calculation to obtain the quadrupole moments of the [523]7/2 − and [404]7/2 + bands. While the [523]7/2 − , [411]1/2 + and [404]7/2 + bands all have similar deformations, the [541]1/2 − band has a quadrupole moment approximately 15% larger. The relative deformations are in good agreement with diabatic potential energy surface calculations performed using the code “Ultimate Cranker”. The experimental crossing frequency, due to the alignment of i 13/2 neutrons, is found to be delayed in the [541]1/2 − band compared to the other bands. This is a universal feature in the rare-earth region, and extensive systematic Cranked Shell Model calculations have been performed to predict deformations and crossing frequencies for nuclei in the region. The model is unable to reproduce the full delay in crossing frequency, confirming that deformation alone is not responsible for the shift.

The nucleus 134 La has been produced using the 124 Sn( 15 N, 5n) reaction. High-spin states have been observed to a maximum spin of 24 + using the CAESAR HPGe array. Bands have been observed that are suggested to be based on the πh 11/2 ⊗νh 11/2 , πh 11/2 ⊗νh 11/2 3 , πh 11/2 ⊗ νg 7/2 h 11/2 2 , and πg 7/2 ⊗νg 7/2 h 11/2 2 configurations. A band fragment, with features similar to the chiral band of 134 Pr, is proposed as the chiral partner of the πh 11/2 ⊗νh 11/2 band.

The structure of 183W has been studied by employing the 176Yb(14C,α 3n) reaction at 68 MeV. Five previously known rotational structure with one-quasiparticle configurations have been extended to higher spin states, and five new rotational bands with three- and five-quasiparticle configurations and a γ-vibration of a one-quasiparticle structure have been newly identified. In the ν7/2-[503] and ν11/2+[615] rotational structures, a signal of an admixture of an octupole- vibrational structure has been observed in their in-band B(M1)/B(E2) ratios and gΚ factors. In the Κπ = 19-M rotational band, a Coriolis effect on the ν1/2-[510] neutron has been identified. In all, 17 Κ-forbidden transitions have been observed. Energies of intrinsic states below 4 MeV have been calculated based on the Blocked BCS theory, and they are used in support of the configuration assignments. © 2000 Elsevier Science B.V. All rights reserved. PACS: 21.10.Re; 21.10.Tg; 23.20.En; 23.20.Lv; 27.70.+q.

The structure of the doubly-odd nucleus 180 Ta has been studied by γ – γ coincidence measurements with a DC beam at 52 and 57 MeV and time-correlated γ – γ coincidence measurements with a pulsed beam at 55 MeV via the 176 Yb( 11 B, α 3n) 180 Ta reaction. In all measurements, γ -rays were detected in coincidence with charged particles. In the time-correlated γ – γ coincidence measurements with a pulsed 11 B beam, three rotational bands and one octupole vibrational band have been identified above the I π =15 − T 1/2 =30 μ s isomer. The configuration of three bands built on 8 + states has been discussed by means of three-band mixing calculations. BCS calculations with blocking have been used in support of configuration assignment of four- and six-quasiparticle structures. Totally, 19 rotational bands, one β -, one γ - and two octupole-vibrational bands, plus one intrinsic state have been identified with two-, four- and six-quasiparticle configurations. The K values of these bands range from 0 to 19. The K-forbidden transition rates are discussed on the basis of mixing between states with widely different K-values. The BBCS calculations predict a K π =22 − isomer not identified experimentally in this nor in previous works. A search for specific intermediate states which could explain the transformation from K π =9 − to 1 + during the astrophysical s- and r- processes was negative.

The structure of 183 W has been studied by employing the 176 Yb( 14 C, α 3n) reaction at 68 MeV. Five previously known rotational structure with one-quasiparticle configurations have been extended to higher spin states, and five new rotational bands with three- and five-quasiparticle configurations and a γ -vibration of a one-quasiparticle structure have been newly identified. In the ν 7/2 − [503] and ν 11/2 + [615] rotational structures, a signal of an admixture of an octupole-vibrational structure has been observed in their in-band B (M1)/ B (E2) ratios and g K factors. In the K π =19 − rotational band, a Coriolis effect on the ν 1/2 − [510] neutron has been identified. In all, 17 K -forbidden transitions have been observed. Energies of intrinsic states below 4 MeV have been calculated based on the Blocked BCS theory, and they are used in support of the configuration assignments.

Excited states in 171Ir have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method. The ground-state band has a structure consistent with an h 11 2 proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation. Band-mixing calculations are performed for 171–175Ir. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for 171–179Ir using the code “Ultimate Cranker”. Dipole bands were also observed, but tilted axis cranking calculations suggest that they are associated with a collective rotation.

In a search for exotic structures in odd-odd 164 Lu, performed as one of the first Euroball experiments eight new, presumably triaxial, superdeformed bands were found. For the first time, evidence is presented for superdeformation in an odd-odd Lu isotope for which theory predicts large triaxiality. The data are compared to expectations from calculations with the code “Ultimate Cranker”. Two of the bands are connected to normal-deformed structures and the E1 strength of the decay-out appears to be enhanced over single particle expectations, possibly due to octupole correlations.

High-spin spectroscopy on odd-odd ${}^{164}\mathrm{Tm}$ has produced new illustrations of departures from the predictions of principal-axis cranking. Among the nine strongly coupled rotational bands observed, four are assigned to the parallel and antiparallel couplings of two configurations $\ensuremath{\pi}{h}_{11/2}\ensuremath{\nu}{i}_{13/2}$ and $\ensuremath{\pi}{g}_{9/2}\ensuremath{\nu}{i}_{13/2}.$ This represents the first time that the high-spin properties of both couplings can be explored. We find that the measured $B(M1)/B(E2)$ values in the $K=1(\ensuremath{\uparrow}\ensuremath{\downarrow})$ coupling of $\ensuremath{\pi}{h}_{11/2}\ensuremath{\nu}{i}_{13/2}$ are 50% larger than those in the $K=6$ (\ensuremath{\uparrow}\ensuremath{\uparrow}) coupling, and represent the largest seen in this nucleus. Tilted-axis cranking calculations successfully explain the $M1/E2$ ratios in these two bands, while the particle-rotor calculations did not reproduce the full low-K enhancement. No inversion in the signatures of the $K=6\ensuremath{\pi}{h}_{11/2}\ensuremath{\nu}{i}_{13/2}$ band is observed, but there is a small inversion in the $K=1$ coupling up to $I=17\ensuremath{\Elzxh}$ and a large inversion in the $\ensuremath{\pi}{h}_{9/2}\ensuremath{\nu}{i}_{13/2}$ band up to $I=19\ensuremath{\Elzxh}.$ Remarkably, particle-rotor calculations with a $p\ensuremath{-}n$ interaction included are able to reproduce these inversions. A stronger $p\ensuremath{-}n$ interaction is needed to explain an inversion in the $\ensuremath{\pi}{d}_{3/2}\ensuremath{\nu}{i}_{13/2}$ band.

Yrast states of Sb-106 have been investigated in the Fe-54(Ni-58, alpha pn) reaction using in-beam gamma-spectroscopic methods and in the Cr-50(Ni-58,pn) reaction performing delayed gamma and conversion electron studies. A new isomeric state was found at 103 keV with t(1/2) = 232(21) ns. The number of start's and transitions in the proposed level scheme have been doubled. The experimental results are discussed within the framework of the shell model. [S0556-2813(99)08502-7].

The γ-decay of the GDR in hot Hg and Eu isotopes has been measured in coincidence with selected low-energy γ-transitions of the evaporation residues. In the Hg case, the GDR width at finite temperature and at different spins was studied by analyzing simultaneously with the statistical model the high-energy γ-ray spectra associated with different residual nuclei and the fractions of residue cross-sections. The measured GDR width was found in good agreement with the predictions of the thermal fluctuations model. In the case of Eu, we have measured the high-energy γ-rays in coincidence with low-energy γ-transitions from different nuclear configurations of 143 Eu in order to search for the GDR decay built on a superdeformed state. The analysis of the data shows a possible evidence of this state. The measured intensity indicates that the superdeformation survives only few MeV above the yrast line.

The nucleus Os-171 has been populated using the reaction Sn-116(Ni-58,2pn). Four new bands are identified, and the previously known bands are extended in spin, to a maximum of 53/2 (h) over bar. On ...

Recent results on the high-spin states of a range of mid- shell nuclei are presented. Coulomb energy differences (CEDs) as a function of spin have been deduced for the mirror pairs and . A quantitative understanding of the variation of the observed CEDs at high spin is presented in terms of rotational alignment and band-termination effects and we show how the shape-change of the nucleus affects the CED. The experimental results for the CEDs are in excellent agreement with the predictions of a full pf-shell model.

Rotational bands in the odd-proton nucleus 171 Lu have been populated with the 160 Gd( 19 F, α4n) reaction. High-spin states were observed to a maximum spin of 73 2 − using the NORD-BALL array. Several new three-quasiparticle bands were observed, including one based on the π 1 2 − [541]⊗ν 7 2 + [633]⊗ν 1 2 − [521] configuration. The signature splitting of this band is inverted from the expected splitting, and this is interpreted as being due to a residual proton-neutron interaction. The contribution of this interaction to the increased crossing frequency observed for the alignment of i 13 2 neutrons in the π 1 2 − [541] band is considered. Strong E1 transitions from high-spin levels in the π 1 2 + [411] band to the π 1 2 − [541] band are observed.

Excited states have been identified for the first time in very neutron deficient Pt-171.172 nuclei using the recoil-or-decay tagging technique. The ground-state band in Pt-172 has been established up to I-pi = 8+. A similar level sequence, presumably built on the I-pi = 13/2(+) state, is observed for Pt-171. The data are compared with theoretical calculations based on the mean field approach and the random phase approximation and are put into the context of the systematics of platinum isotopes. (C) 1998 Elsevier Science B.V. All rights reserved.

The nucleus 162Tm has been populated by the 130Te(37Cl,5n) reaction, and the γ-cascades detected with the NORDBALL array. Eight coupled rotational bands involving the proton orbitals, g 7 2 [404] 7 2 + , d 3 2 [411] 1 2 + , d 5 2 [402] 5 2 + , h 11 2 [523] 7 2 − and h 9 2 [541] 1 2 − and neutron orbitals i 13 2 [642] 5 2 + , h 9 2 [523] 5 2 − and f 7 2 [521] 3 2 − have been established in 162Tm, to spins varying from 18 to 47ℏ. Various phenomena which can be related to residual neutron-proton interactions are discussed. In particular, signature inversion in the π [541]1 2 − ⊗ ν [642]5 2 + bands based on the h 9 2 quasiproton and i 13 2 quasineutron, rewpectively, may be explained by a fairly large p-n interaction. In addition, interactions at the crossings of bands with constituent quasiparticles differing both in parity and signature have been extracted with strength of the order of a few (4–12) keV. Such interactions also require terms beyond the standard mean field description.

High-spin states in 183Re have been studied using the 176Yb(11B,4n) reaction at 52 and 57 MeV. Two high-K bands have been observed directly by a time-correlated γ-γ coincidence measurement. One of the bands is built on an isomeric Kπ=(25/2)+ state at Ex= 1908 keV with a half-life of 0.82(2) ms. The other band, assigned as Kπ=(29/2)− at Ex= 2739 keV, decays to the (25/2)+ band. These bands are interpreted as three-quasiparticle structures, π(5/2)+[402] &⊗ν(9/2)+[624] ⊗ν(11/2)+[615] for the (25/2)+ band and π(9/2)−[514] ⊗ν(9/2)+[624] ⊗ν(11/2)+[615] for the (29/2)− band. The Kπ= (29/2)− band becomes strongly Coriolis mixed with increasing spin and is gradually changing into a low-K s-band structure.

Six rotational bands in the odd-odd nucleus 174Ta have been populated with the 160Gd(19F,5n) reaction. High-spin states were identified using the NORDBALL array. Both signatures of the doubly decoupled π 1 2 − [541] ⊗ ν 1 2 − [521] band and semi-decoupled π 1 2 − [541] ⊗ ν 7 2 − [633] band are observed, in addition to the high-K couplings of the π 9 2 − [514] ⊗ ν 7 2 + [633] , π 9 2 − [514] ⊗ ν 5 2 − [512] , π 7 2 + [404] ⊗ ν 7 2 + [633] , and π 5 2 + [402] ⊗ ν 5 2 − [512] configurations. The signature splitting of the π 1 2 − [541] ⊗ ν 7 2 + [633] band is inverted from the expected splitting, and this is interpreted as being due to a residual proton-neutron interaction. It is shown empirically that this interaction, together with deformation changes, can account for the increased crossing frequency associated with the alignment of i 13 2 neutrons in the π 1 2 − [541] bands of odd-Z nuclei.

High-spin states have been investigated in the mirror pair nuclei {sup 49}Cr (Z=24, N=25) and {sup 49}Mn (Z=25, N=24). Mirror symmetry up to the band termination at about 10.7MeV has been established. A comparison of the corresponding energy levels of the pair shows, for the first time, that the Coulomb energy difference approaches zero as the band termination is approached. This is explained intuitively in terms of a pure f{sub 7/2} shell framework. For {sup 49}Cr, excellent agreement is found between the data and recent full pf-shell calculations. {copyright} {ital 1997} {ital The American Physical Society}

The lifetime of the unresolved transitions forming the rotational quasi-continuum spectra has been measured in 163 Tm using the Doppler shift attenuation technique. Spectra associated to different values of the coincidence folds, angular anisotropies and the dynamical moment of inertia were also obtained from the present experiment. The Doppler shift has been measured for discrete transitions, for the ridge structures in E γ 1 × E γ 2 spectra and for the rotational E2 bump in one dimensional spectra. The data were compared to the theory using a simulation model which makes use of microscopically calculated levels and transition probabilities. Above 1300 keV the results indicate collectivity with lifetime faster than 10 −14 s, while at lower E γ the results are well described by predictions with B (E2) = 400 WU.

High-spin states in 177 W have been populated using the 164 Dy( 18 O,5n) reaction at a beam energy of 83 MeV. Six new high- K bands based on 3-, 5- and 7-quasiparticle excitations have been observed. Nilsson configurations for these bands are discussed, and experimental and calculated g -factors are compared. Decays of the K π = 29 2 + 5-quasiparticle state to the members of the K π = 7 2 + band have been observed. The decay rates are compared with predictions calculated within a tunneling model where the nuclear shapes are considered to change along the γ direction in the ( ϵ 2 , γ) deformation plane.

Excited states in Cd-98, two proton holes from Sn-100, were identified and studied for the first time, using in-beam spectroscopy with highly selective ancillary detectors. The structure of the (pi g(9/2))(-2) two-proton-hole spectrum below a T-1/2 = 0.48(16) mu s isomer is deduced and compared to shell-model predictions. A tentative I-pi = (8(+)) assignment, as suggested by systematics, yields a strongly reduced B(E2,8(+) --> 6(+)) = 0.44((+20)(-10)) W.u., corresponding to an effective proton charge of e(pi) = 0.85((+20)(-10))e, which is at variance with existing theoretical predictions.

Semi-decoupled bands based on the πh 9 2 ⊗ vi 13 2 configuration are observed in 162 Tm, 164 Tm and 174 Ta. Spins assigned to these bands imply an inversion of the expected signature splitting, which is interpreted as being the result of a residual proton-neutron interaction.

Using the (18O,5n) 163Er reaction a multitude of rotational bands have been established with firm spin and parity assignments in 163Er. In 17 out of 24 band crossings E2 cross-band transitions have been observed. The interaction strength varies between ∼ 1 and ∼ 50 keV with many of the values in the range 10–15 keV. These interactions sample a variety of the lowest (multi) -quasiparticle configurations. For some bands, in particular those with high K-values, the configurations can be established rather well. Quite complicated changes in the wavefunctions must occur at these crossings, and to explain the observed interaction strengths coupling to various vibrational degrees of freedom, in addition to possible residual neutron-proton interactions, may be needed.

The nucleus 102Pd has been studied using 148 MeV 34S ions impinging on 76Ge. The γ-rays were detected with the Nordball array and the light charged particles with a 4π charged particle detector system. Rotational bands have been extended using γ-ray yields, γγ coincidences and angular correlation information. Calculated spin diabatic surfaces were used for assigning quasiparticle configurations to the bands. The (+,0) high spin band extending to 26+ may be explained by a π( g 9 2 ) 2 ⊗ ν(“ g 7 2 ”) 2 quasiparticle configuration. The protons are predicted to align first. The negative parity bands are suggested to be built on ν (“ g 7 2 ” h 11 2 ) evolving to π( g 9 2 ) 2 ⊗ ν(“ g 7 2 ” h 11 2 ) at the highest spins.

An experimental investigation of the nucleus 165Lu, using the reactions 138Ba(31P,4n) 165Lu and 150Sm(19F,4n) 165Lu at beam energies of E = 155 and 95 MeV, respectively, has been performed. Among other additions to the existing level scheme, a new band, with transition energies almost identical to a strongly deformed (β2 0.42) πi13/2[660 1/2+] band recently discovered in 163Lu has been established. A theoretical analysis of the structure of the two Lu isotopes, 165Lu and 163Lu is carried out by detailed calculations of total potential energy surfaces for specific configurations. By a diabatic treatment of crossings specific proton configurations as πi13/2[660 1/2+] are identified throughout the deformation space and as a function of spin. It is found as a general feature that well deformed local minima of considerable nonaxial symmetry coexist with a normal deformed global minimum. The depth of these local minima depend on configuration. The structure of the different global and local minima found in these surfaces are analysed and discussed in terms of occupation of available basis configurations and their orientation relative to the rotation axis. The strongly deformed minima are found to belong to a group of superdeformed triaxial structures, expected to appear at low energies for certain favourable combinations of proton and neutron numbers.

High spin states in 105Cd have been studied using reactions 106Cd(p, pn), 106Cd(3He, 2p2n), 92Zr(16O, 3n) and 76Ge(34S, 5n). The excited levels are dominated by a negative parity band structure up to spin 47 2 − and a positive parity structure up to spin 27 2 + . The negative parity structure is based on ν h 11 2 excitations and undergoes a band crossing at h ω ≈ 0.44 MeV . This band crossing is interpreted as an alignment of a g 7 2 neutron pair. The positive parity excitations are understood as due to ν g 7 2 and ν d 5 2 configurations. The results are discussed in terms of spin diabatic surface calculations.

High-spin states in 182W have been studied using the 176Yb(13C,α3n) reaction at a beam energy of 65 MeV. The ground state band is found to backbend clearly at h ω ≈ 0.38 MeV and to gain more than 6 units of angular momentum. In addition, the Kπ = 10+ band is observed to decay into the g.s.b. 16+ state where the yrast sequence backbends. Three-band mixing calculations between the g-, s- and Kπ = 10+ bands have been performed to interpret the backbend. Comparison of the experimental gK factors with predictions confirms configuration assignments and allows new assignments for some of the bands. The level scheme of high-K four-quasiparticle states recently reported is corrected, and the intrinsic structures are discussed in more detail.

High-spin properties of rotational bands are studied in 173Ta using the 160Gd(19F,6n) reaction at bombarding energies of 103–105 MeV. With the existing bands being extended, and new bands established, a total of 16 rotational sequences are interpreted in terms of their (multi) quasiparticle structure. Measurements of electromagnetic properties for these bands include E2 M1 mixing ratios, branching ratios and lifetimes of isomeric states close to band heads, for which all energies have now been determined. Particular emphasis is devoted to (i) the band structures related to the 1 2 − [541] intruder configuration, for which both favoured, and unfavoured partners as well as the extended g- and S-bands in the (delayed) crossing region have been established, (ii) the reduced E1 transition strength between the (new) 1 2 + [411] and 1 2 − [541] bands, which is strongly enhanced, most likely due to coupling to octupole degrees of freedom, and show a ΔI = 4 staggering, (iii) the observation of weak interband transitions between the two partners of a pseudo-spin doublet composed of the 5 2 + [402] and 7 2 + [404] bands together with accurately measured intraband mixing ratios enable an analysis of the mixing of these bands through comparisons to particle-rotor calculations, (iv) the observed three-quasiparticle bands which are assigned to specific configurations coupling the lowest protons to lowest two-quasineutrons with negative parity.

The {pi}{ital i}{sub 13/2}(1/2{sup +}[660]) and {pi}{ital h}{sub 9/2}(1/2{sup {minus}}[541]) bands of {sup 175}Re and {sup 177}Ir are extended to high spins with the reactions {sup 161}Dy({sup 19}F, 5{ital n}){sup 175}Re and {sup 146}Nd({sup 35}Cl, 4{ital n}){sup 177}Ir. Band crossings are observed which are attributed to the alignment of {ital i}{sub 13/2} neutrons. In the case of the {pi}{ital i}{sub 13/2} bands, a study of the alignments implies a reduction in deformation at the crossing. In {sup 177}Ir the yrare extensions of the one- and three-quasiparticle {pi}{ital i}{sub 13/2} bands are observed for the first time, enabling relative quadrupole moments to be deduced. These support a loss of deformation in the three-quasiparticle {pi}{ital i}{sub 13/2} bands. The interaction between the bands is 77.3 keV. Therefore, up-bends at low frequency in the {pi}{ital i}{sub 13/2} bands are attributed to deformation effects rather than strong interactions.