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Excited states in the neutron-deficient nuclei 75163Re88 and 75165Re90 were populated in the 106Cd(60Ni. p2nγ) and 92Mo(78Kr, 3p2nγ) fusion-evaporation reactions at bombarding energies of 270 and 380 MeV, respectively. γ rays were detected at the target position using the JUROGAM spectrometer while recoiling ions were separated in-flight by the RITU gas-filled recoil separator and implanted in the GREAT spectrometer. The energy level schemes for 163Re and 165Re were identified using recoil-decay correlation techniques. At low spin, the yrast bands of these isotopes consist of signature partner bands based on a single πh11/2 quasiproton configuration. The bands display large energy splitting consistent with the soft triaxial shape typical of transitional nuclei above N = 82. The configurations of the excited states are proposed within the framework of the cranked shell model. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-deficient isotopes 163Os and 165Os were identified using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator. The 163Os and 165Os nuclei were populated via the 106Cd(60Ni,3n) and 92Mo(78Kr,2p3n) reactions at bombarding energies of 270 MeV and 357 MeV, respectively. Gamma-ray emissions from these nuclei have been established unambiguously using the recoil-decay tagging technique and a coincidence analysis has allowed level schemes to be established. These results suggest that the yrast states are based upon negative-parity configurations originating from the vf7/2 and vh9/2 orbitals. [ABSTRACT FROM AUTHOR]

Lifetimes of the low-lying excited states in the very neutron-deficient nucleus 175Au have been measured by the recoil-distance Doppler-shift method using γ-ray spectra obtained with the recoil-decay tagging technique. Transition quadrupole moments and reduced transition probabilities extracted for this odd-Z nucleus indicate the existence of three different shapes and the competition between collective and noncollective structures. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-deficient odd-Z nuclide 161Ta were identified for the first time using the 106Cd(58Ni,3pγ) reaction at a beam energy of 270 MeV. The πh11/2 band, yrast at low spin, was observed up to (47/2¯) and a further four strongly coupled bands have been established to high spin. Quasiparticle configuration assignments for the new band structures have been made on the basis of cranked shell model calculations. This work suggests that the negative-parity γ(f7/2,h9/2) orbitals are responsible for the first rotational alignment in the πh11/2 band. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-deficient nuclides 16274W88 and 16474W90 were investigated by using the γ-ray spectrometer Jurogam. A change in structure is apparent from the first rotational alignments in 162W and 164W, whose rotationally aligned bands are interpreted as ν(h9/2)² and ν(i13/2)² configurations, respectively. The level schemes have been extended using recoil (-decay) correlations with the observation of excited collective structures. Configuration assignments have been made on the basis of comparisons of the deduced aligned angular momentum, as a function of rotational frequency, with the predictions of the cranked shell model. [ABSTRACT FROM AUTHOR]

An isomeric state at high spin and excitation energy was recently observed in the proton-unbound nucleus 158Ta. This state was observed to decay by both α and γ decay modes. The large spin change required to decay via γ-ray emission incurs a lifetime long enough for α decay to compete. The α decay has an energy of 8644(11) keV, which is among the highest observed in the region, a partial half-life of 440(70) µs and changes the spin by 11ħ. In this paper, additional evidence supporting the assignment of this α decay to the high-spin isomer in 158Ta will be presented. [ABSTRACT FROM AUTHOR]

A multiparticle spin-trap isomer has been discovered in the proton-unbound nucleus 15873Ta85. The isomer mainly decays by γ-ray emission with a half-life of 6.1(1) μs. Analysis of the γ-ray data shows that the isomer lies 2668 keV above the known 9+ state and has a spin lOh higher and negative parity. This 19- isomer also has an 8644(11) keV, 1.4(2)% α-decay branch that populates the 9+ state in 154Lu. No proton-decay branch from the isomer was identified, despite the isomer being unbound to proton emission by 3261(14) keV. This remarkable stability against proton emission is compared with theoretical predictions, and the implications for the extent of observable nuclides are considered. [ABSTRACT FROM AUTHOR]

Excited states and decay properties of 175Pt have been investigated using the 92Mo(86Sr,2pn) fusion-evaporation reaction. The JUROGAM I γ-ray spectrometer and the GREAT spectrometer were used in conjunction with the gas-filled recoil separator RITU for the measurement of the radiation at the target and focal plane positions, respectively. Two new band structures, assigned to be based on the Iπ = (7/2-) ground state in 175Pt, have been established and the known yrast band has been extended up to Iπ = (49/2+). Rotational properties of the excited states in 175Pt have been investigated within the cranked shell-model formalism. The low-frequency changes in the alignments of the positive- and negative-parity bands are interpreted as a sign of proton-pair excitations in the rotating core. Furthermore, the a-decay measurements reveal a candidate for a fourth a-decay branch in 175Pt, feeding a non-yrast state in 171Os. [ABSTRACT FROM AUTHOR]

Excited states have been identified in the isotones Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. and Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., which were produced in fusion-evaporation reactions of a beam of 310-MeV 58Ni ions with an isotopically enriched 106Cd target. The strengest γ-ray transitions in 159W and 160Re are interpreted as continuing the regular sequence of states identified in lighter N = 85 isotones that are built upon 9/2- and 10+ states, respectively. The half-life of 155Hf, the β-decaying daughter of the α decay of 159W, was measured with improved precision to be 840 ± 30 ms. [ABSTRACT FROM AUTHOR]

The decays of the πd3/2 ground states of 156Ta and 160Re have been studied in detail using the GREAT spectrometer. More than 7000 160Re nuclei were produced in reactions of 290- and 300-MeV 58Ni ions with an isotopically enriched 106Cd target and separated in flight using the RITU separator. The proton and α decays of the πd3/2 level were confirmed and the half-life and branching ratios of this state were determined with improved precision to be t1/2 = 611 ± 7 μs and bp = 89 ± 1% and bα = 11 ± 1%, respectively. The α-decay branch populated the ground state of 156Ta, allowing improved values for the proton-decay energy and half-life to be obtained (Ep = 1011 ± 5 keV; t1/2 = 106 ± 4 ms). The β decay of this level was identified for the first time and a branching ratio of bβ = 29±3% was deduced. The spectroscopic factors deduced from these measurements are compared with predictions. [ABSTRACT FROM AUTHOR]

High-spin states in the N = 128 nucleus 218Th have been investigated following fusion–evaporation reactions, using the recoil-decay tagging technique. Due to the short-lived nature of the ground state of 218Th prompt γ rays have been correlated with the α decay of the daughter nucleus 214Ra. The level scheme representing the decay of excited states has been extended to (16+) with the observation of six previously unreported transitions. The observations are compared with the results of shell model calculations and within the context of the systematics of neighbouring nuclei. [ABSTRACT FROM AUTHOR]

The β + /EC decay of mass separated samples of 181 Hg was studied employing the TATRA spectrometer at the ISOLDE facility at CERN. The decay scheme was constructed for the first time. A Broad Energy Germanium detector was used to achieve this by combination of high-gain γ -ray singles spectroscopy and γ – γ coincidences. The systematics of excited states associated with the 1 h 11 / 2 proton-hole configuration in odd-Au isotopes was extended. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-deficient odd-odd proton-unbound nuclide 158Ta have been investigated in two separate experiments. In the first experiment, 166Ir nuclei were produced in the reactions of 380 MeV 78Kr ions with an isotopically enriched 92Mo target. The α-decay chain of the 9+ state in 166Ir was analyzed. Fine structure in the α decay of the 9+ state in 162Re established a 66 keV difference in excitation energy between the lowest-lying 9+ and 10+ states in 158Ta. Higher-lying states in 158Ta were populated in the reactions of 255 MeV Ni58 ions with an isotopically enriched 102Pd target. Gamma-ray decay paths that populate, depopulate, and bypass a 19- isomeric state have been identified. The general features of the deduced level scheme are discussed and the prospects for observing proton emission branches from excited states are considered. [ABSTRACT FROM AUTHOR]

Excited states in the odd-odd, highly neutron-deficient nucleus 166Re have been investigated via the 92Mo(78Kr,3p1n)166Re reaction. Prompt γ rays were detected by the JUROGAM II γ-ray spectrometer, and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and implanted into the Gamma Recoil Electron Alpha Tagging spectrometer located at the RITU focal plane. The tagging and coincidence techniques were applied to identify the γ-ray transitions in Re166, revealing two collective, strongly coupled rotational structures, for the first time. The more strongly populated band structure is assigned to the πh11/2[514]9/2- ⊗ νi13/2[660]1/2+ Nilsson configuration, while the weaker structure is assigned to be built on a two-quasiparticle state of mixed πh11/2[514]9/2- ⊗ ν[h9/2f7/2]3/2- character. The configuration assignments are based on the electromagnetic characteristics and rotational properties, in comparison with predictions from total Routhian surface and particle-rotor model calculations. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-deficient nucleus 72161Hf89 have been populated using the 118Sn(48Ti,5n) 161Hf and 110Pd(56Fe,5n) 161Hf fusion-evaporation reactions at 240 and 270 MeV, respectively. The level scheme for 161Hf has been extended with the observation of new band structures and an Iπ = (13/2+) isomeric state with a half-life of 4.8(2) μs has been identified. The decay path from this isomer to the (7/2-) ground state is established. The yrast band, based on the (13/2+) isomeric state, is extended up to (73/2+) and side band structures are identified up to (69/2-) and (55/2-). Quasiparticle assignments for these rotational structures are made on the basis of their alignment properties and Woods-Saxon cranked shell-model calculations. [ABSTRACT FROM AUTHOR]

The neutron-deficient mercury isotopes, 184,186Hg, were studied with the recoil distance Doppler-shift method using the Gammasphere array and the Köln plunger device. The differential decay curve method was employed to determine the lifetimes of the yrast states in 184,186Hg. An improvement on previously measured values of yrast states up to 8+ is presented as well as first values for the 93 state in 184Hg and 10+ state in 186Hg. B(E2) values are calculated and compared to a two-state mixing model which utilizes the variable moment of inertia model, allowing for extraction of spin-dependent mixing strengths and amplitudes. [ABSTRACT FROM AUTHOR]

A detailed nuclear-decay spectroscopy study of the neutron-deficient isotope 178T1 has been performed using the highly selective Resonance Ionization Laser Ion Source and ISOLDE mass separator (CERN), which allowed a unique isobarically pure beam of 178T1 to be produced. The first identification of the ß-delayed fission of this isotope was made and its probability PßDf(I78T1) = 0.15(6)% was determined. An asymmetric fission fragment mass distribution of the daughter isotope l78Hg (populated by the ß decay of 178T1) was deduced based on the measured fission fragment energies. The fine-structure a-decay pattern of I78T1 allowed the low-energy states in the daughter nucleus 174Au to be studied. [ABSTRACT FROM AUTHOR]

The α-decay chains originating from the πS1/2 and πh11/2 states in 173Au have been investigated following fusion-evaporation reactions. Four generations of a radioactivities have been correlated with 173Aum leading to a measurement of the a decay of 16lTam. It has been found that the known α decay of 161Tam, which was previously associated with the decay of the ground state, is in fact the decay of an isomeric state. This work also reports on the first observation of prompt γ rays feeding the ground state of 173Au. This prompt γ radiation was used to aid the study of the α-decay chain originating from the πs1/2 state in 173Au. Three generations of a decays have been correlated with this state, leading to the observation of a previously unreported activity which is assigned as the decay of 165Reg. This work also reports the excitation energy of an α-decaying isomer in 161Ta and the Qa value of the decay of 161Tag. [ABSTRACT FROM AUTHOR]

The neutron-deficient nucleus 173Hg has been studied following fusion-evaporation reactions. The observation of the decay of excited states via &ggr; radiation are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighboring neutron-deficient Hg nuclei. In addition to the &ggr;-ray spectroscopy, the a decay of this nucleus has been measured yielding superior precision to earlier measurements. [ABSTRACT FROM AUTHOR]

An experiment to search for the a decay of 112Cs has been performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. The a decay of 112Cs was not observed, thus setting the upper limit of the &agr; branching ratio at 0.26%. The half-life of 112Cs was measured as 506±55μs. In the same measurement the decay properties of its proton decay daughter 111Xe were also reinvestigated. The newly measured a branching ratio for 111Xe is 10.4 ± 1.9 %. The experimental proton separation energies Sp for odd-Z nuclei above l0OSn were compared to shell model calculations. The calculated proton separation energies for 103Sb and 102Sb point to half-lives of the order of 10 ps and 1 ns, respectively. [ABSTRACT FROM AUTHOR]

Excited states in 180Hg were populated using the 147Sm(36Ar,3n)180Hg reaction and studied by in-beam conversion-electron spectroscopy. Conversion electrons emitted at the target position were measured using the Silicon Array for Conversion Electron Detection (SACRED) spectrometer and tagged through the characteristic decays of 180Hg detected in a position-sensitive silicon strip detector located at the focal plane of the gas-filled recoil separator Recoil Ion Transport Unit (RITU). Electron conversion of transitions previously assigned to 180Hg through in-beam v-ray spectroscopy studies was identified up to the 10+ → 8+ transition and the intensities of the conversion-electron transitions were found to be consistent with the previous multipolarity assignments. Evidence was also found for two highly converted transitions in 180Hg: a 167 keV transition is interpreted as the transition from the newly identified Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed, while a 420 keV transition is assigned as the E0 decay from the 0+ bandhead of the prolate-deformed configuration to the weakly deformed ground state. [ABSTRACT FROM AUTHOR]

By exploiting the SAGE spectrometer a simultaneous measurement of conversion electrons and γ rays emitted in the de-excitation of excited levels in the neutron-deficient nuclei 184,186Hg was performed. The light Hg isotopes under investigation were produced using the 4n channels of the fusion-evaporation reactions of 40Ar and 148,150Sm. The measured K- and L-conversion electron ratios confirmed the stretched E2 nature of several transitions of the yrast bands in 184,186Hg. Additional information on the E0 component of the 22+→21+ transition in 186Hg was obtained. [ABSTRACT FROM AUTHOR]

High-spin states in161Lu were investigated using the EUROBALL spectrometer. A previously known triaxial superdeformed band has been extended to higher spins and a new band with similar characteristics has been discovered. Comparison to systematically occurring wobbling bands in Lu isotopes strongly suggests that these two bands represent thenw = 0 and 1 wobbling excitations in161Lu. [ABSTRACT FROM AUTHOR]

Four ΔI=1 bands consisting of strong magnetic dipole transitions have been observed in 133Pr, produced in the 100Mo(37Cl,4nγ) reaction, using the Eurogam II γ-ray spectrometer. The structure of three of these bands is discussed in terms of prolate high-K configurations, related to the Iπ=Kπ=8− isomeric state (νh11/2g7/2) in the 132Ce core. The fourth band, with a reduced moment of inertia, is interpreted as a collectively rotating oblate structure involving rotationally aligned h11/2 neutrons. [Copyright &y& Elsevier]

Presents a study which described a novel triggerless data acquisition method which is being developed for the gamma recoil electron alpha tagging spectrometer. Information on the conventional recoil decay tagging; Details of the total detail readout method; Conclusion.

The electron spectrometer, SPEDE, has been developed and will be employed in conjunction with the Miniball spectrometer at the HIE-ISOLDE facility, CERN. SPEDE allows for direct measurement of internal conversion electrons emitted in-flight, without employing magnetic fields to transport or momentum filter the electrons. Together with the Miniball spectrometer, it enables simultaneous observation of γ rays and conversion electrons in Coulomb excitation experiments using radioactive ion beams. [ABSTRACT FROM AUTHOR]

The triple α-decay chain 114Ba→110Xe→106Te→102Sn has been directly observed for the first time, following the 58Ni(58Ni,2n) reaction. Implantation of 114Ba nuclei into a double-sided silicon-strip detector has allowed their α decays to be correlated in position and time with the α decays of the daughter (110Xe) and granddaughter (106Te) nuclei. In total, 17 events have been assigned to the 114Ba→110Xe→106Te→102Sn triple α-decay chain. The energy of the 114Ba α decay has been measured to be Eα=3480(20) keV, which is 70 keV higher than the previously measured value, and the half-life of 114Ba has been measured with improved accuracy, to be 380+190-110 ms. A revised Q12C value of 19 035(45) keV for 114Ba is presented. [ABSTRACT FROM AUTHOR]

Lifetimes of excited states in the neutron-deficient odd-odd nucleus 166Re have been measured for the first time using the recoil distance Doppler-shift method. The measured lifetime for the (8-) state; τ=480 (80) ps, enabled an assessment of the multipolarities of the γ rays depopulating this state. Information on electromagnetic transition strengths were deduced for the γ-ray transitions from the (9-),(10-), and (11-) states, and in the case of the (10-) and (11-) states limits on the B(M1) and B(E2) strengths were estimated. The results are compared with total Routhian surface predictions and semiclassical calculations. Tilted-axis cranking calculations based on a relativistic mean-field approach (TAC-RMF) have also been performed in order to test the possibility of magnetic rotation in the 166Re nucleus. While the TAC-RMF calculations predict a quadrupole-deformed nuclear shape with similar β2 deformation as obtained by using the TRS model, it was found that the experimental electromagnetic transition rates are in better agreement with a collective-rotational description. [ABSTRACT FROM AUTHOR]