Search

High-spin states in Xe-123 were populated in the Se-80(Ca-48, 5n) Xe-123 reaction at a beam energy of 207 MeV. gamma-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus. The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov models. It is concluded that the configurations of the bands involve two-proton excitations across the Z = 50 as well as excitation of neutrons across the N = 82 shell gaps resulting in a large deformation, epsilon(2) approximate to 0.30 and gamma approximate to 5 degrees.

An experiment involving a heavy-ion-induced fusion-evaporation reaction was carried out where high-spin states of Xe123 were populated in the Se80(Ca48,5n)Xe123 reaction at 207 MeV beam energy. Gamma-ray coincidence events were recorded with the Gammasphere Ge detector array. The previously known level scheme was confirmed and enhanced with the addition of five new band structures and several interband transitions. Cranked Nilsson-Strutinsky (CNS) calculations were performed and compared with the experimental results in order to assign configurations to the bands.

Recent technological developments considerably lowered the barrier for unmanned aerial systems (UAS) to be employed in a variety of usage scenarios, comprising live video transmission from otherwise inaccessible vantage points. As an example, in the French-German ANCHORS project several UAS guided by swarm intelligence provide aerial views and environmental data of a disaster site while deploying an ad-hoc communication network for first responders. Since being able to operate in harsh environmental conditions is a key feature, the immunity of the UAS against radio frequency (RF) exposure has been studied. Conventional Electromagnetic Compatibility (EMC) applied to commercial and industrial electronics is not sufficient since UAS are airborne and can as such move beyond the bounds within which RF exposure is usually limited by regulatory measures. Therefore, the EMC requirements have been complemented by a set of specific RF test frequencies and parameters where strong sources are expected to interfere in the example project test case of an inland port environment. While no essential malfunctions could be observed up to field strengths of 30 V m−1, a sophisticated, more exhaustive approach for testing against potential sources of interference in key scenarios of UAS usage should be derived from our present findings.Recent technological developments considerably lowered the barrier for unmanned aerial systems (UAS) to be employed in a variety of usage scenarios, comprising live video transmission from otherwise inaccessible vantage points. As an example, in the French-German ANCHORS project several UAS guided by swarm intelligence provide aerial views and environmental data of a disaster site while deploying an ad-hoc communication network for first responders. Since being able to operate in harsh environmental conditions is a key feature, the immunity of the UAS against radio frequency (RF) exposure has been studied. Conventional Electromagnetic Compatibility (EMC) applied to commercial and industrial electronics is not sufficient since UAS are airborne and can as such move beyond the bounds within which RF exposure is usually limited by regulatory measures. Therefore, the EMC requirements have been complemented by a set of specific RF test frequencies and parameters where strong sources are expected to interfere in the example project test case of an inland port environment. While no essential malfunctions could be observed up to field strengths of 30 V m−1, a sophisticated, more exhaustive approach for testing against potential sources of interference in key scenarios of UAS usage should be derived from our present findings.

International audience; High-spin states in Xe-124 have been populated using the Se-80(Ca-48,4n) reaction at a beam energy of 207 MeV and high-multiplicity, gamma-ray coincidence events were measured using the Gammasphere spectrometer. Six high-spin bands with large moments of inertia, similar to those observed in neighboring nuclei, have been observed. The experimental results are compared with calculations within the framework of the cranked Nilsson-Strutinsky model. It is suggested that the configurations of the bands involve excitations of protons across the Z = 50 shell gap coupled to neutrons within the N = 50-82 shell or excited across the N = 82 shell closure.

The lineshapes and peak position of Doppler corrected γ -ray spectra from in-beam experiments at relativistic energies are investigated with respect to the intrinsic energy resolution of the employed detectors, the particles’ velocities, and the photons’ emission angle uncertainties at the moment of γ -ray emission. The uncertainties in velocity and photon emission angle are dependent on the lifetime of the excited state. The impact of these two observables on the lineshape and energy resolution are studied for the RISING γ -spectrometer by means of simulations and experimental results from a two-step fragmentation experiment at ≈ 200 MeV / u . Potential use of the distinct lineshape for lifetime determination is demonstrated for measured γ -ray transitions.

The spectroscopic quadrupole moments of the 11(-) and 12(+) isomers in Pb-192,Pb-194, described by the 3s(1/2)(-2)1h(9/2)1i(13/2) intruder two-proton and 1i(13/2)(2) two-quasi neutron configurations, respectively, have been determined by the method of time-differential observation of the gamma-ray perturbed angular distribution. The derived values are vertical bar Q(s)vertical bar(12(+),Pb-192) = 0.32(4) eb, vertical bar Q(s)vertical bar(11(-),Pb-192) = 2.9(3) eb and vertical bar Q(s)vertical bar(11(-),Pb-194) = 3.6(4) eb. The 8(+) 2304 keV and 9(-) 2514 keV states in Pb-192 have been identified as isomers, with half-lives of 3.9(3) and 3.3(2) ns, respectively. The experimental spectroscopic quadrupole moments for the 11(-) and 12(+) isomers in neutron deficient Pb nuclei have been described in the framework of the pairing plus quadrupole model. The intrinsic quadrupole moments and deformation of the 11(-) isomers are compared with the predictions of mean-field and interacting boson models. (C) 2007 Elsevier B.V. All rights reserved. ispartof: Physics Letters B vol:650 issue:2 pages:141-147 status: published

An activation technique was used to investigate relative yields of fission products from the reaction 232Th(n, f ) for neutron energies between 1.3 and 1.8MeV covering the region around the first hyperdeformed resonances. Intensities of characteristic γ-ray transitions were analyzed to search for changes in the mass distribution for neutron energies corresponding to the resonances and below the resonances. Relative increases in yield between 7 and 23% are observed for A ≈ 100 and 132 in the resonance region around 1.6MeV. It is proposed that the yield enhancement of daughter nuclei of the preformed fragments 132Sn and 101Zr arises from cold fission of a di-cluster configuration. The experimental results support theoretical predictions for the existence of hyperdeformed octupole shapes based on the di-nuclear configuration 132Sn + 101Zr.

The first excited 2+2+ state of 36Ca has been identified by its γ -decay, exploiting the two-step fragmentation technique at the FRS-RISING setup at GSI. This is the heaviest Tz=−2Tz=−2 nucleus in the Segré chart in which a γ-decay of an excited state has been observed. A stable beam of 40Ca at View the MathML source420AMeV impinged on a primary 9Be target. Out of the secondary beam of fragmentation products, 37Ca was separated by the FRS and struck on a second 9Be target at the final focus of the FRS. The energy for the View the MathML source21+ decay of 36Ca was determined to be 3015(16) keV, which is 276 keV lower than in its T=2T=2 mirror 36S. This mirror energy difference (MED) is discussed in the framework of shell model calculations using a 16O core, the sd shell isospin symmetric interaction USD and experimental single-particle energies from 17O and 17F. The results show that the MED within the sd shell provide a sensitive test for the evolution of the N , Z=14,16Z=14,16 subshell gaps towards the driplines. Especially the N , Z=16Z=16 gap is determined by Thomas–Ehrman shift in the A=17A=17, T=1/2T=1/2 isospin doublet, while Coulomb effects are found to have marginal influence. ispartof: Physics Letters B vol:647 issue:4 pages:237-242 status: published

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554; International audience; The Scintilla FP7 project is ended in December 2014, the fruitful results of 3 years development and tests will be presented. SCINTILLA offers the capacity to finding a reliable alternative to Helium-3 based detection systems since the gas which is predominantly used in nuclear safeguards and security applications has now become very expensive, rare and nearly unavailable. SCINTILLA benchmarks results are based on international standards. Radiation Portal tests were carried out at the Joint Research Centre (JRC) in Ispra (Italy). The scintilla project addresses few main issues. The first is to develop neutron detectors for Radiation Portal Monitor (RPM) and the second is the need of new wearable integrated solutions for Spectrometric Personal Radiation Monitor (SPRM). The partners which provide technical systems of the scintilla project are INFN-ANSALDO, CEA, SYMETRICA and SAPHYMO. For RPM, the objective is to find reliable alternatives to Helium-3 historical neutron detector and provide technical solutions which cope with tests for reliable mobile and cost effective. For Spectrometric Personal Radiation Monitor (SPRM), SCINTILLA is innovating in technology areas that offer complementary capabilities for detecting and identifying gamma Two CZT (Cadmium Zinc Telluride) addressing contexts of used by first responder technologies, one is a wearable detector and the second is a gamma camera complemented by advanced image processing technologies.

The collective structures of 131Cs have been investigated by in-beam γ-ray spectroscopic techniques following the 124Sn (^11B , 4n) reaction at a beam energy Elab = 57MeV. The previously established rotational bands, built on πg7/2, πd5/2 and the unique-parity πh11/2 orbitals, have been extended and evolve into new bands involving rotationally aligned ν(h11/2)2 and π(h11/2)2 quasiparticles. In addition, a new multiquasiparticle band based on the πg7/2 ⊗ νg7/2 ⊗ νh11/2 configuration has also been observed. Theoretical interpretations for the assigned configurations are discussed in the framework of Total Routhian Surface (TRS) and Tilted Axis Cranking (TAC) model calculations. TAC model calculations predict a decrease in the B(M1) values with increasing rotational frequency for the πg7/2/πd5/2 ⊗ ν(h11/2)2 and πh11/2 ⊗ ν(h11/2)2 bands, thus indicating a magnetic rotation character for these bands.

The recently measured spectroscopic quadrupole moments of the 11 − intruder isomers in 194,196 Pb are being discussed in the particle-core coupling model. The essential physics behind the nature of these isomers is revealed by a simple two-level-mixing calculation, showing that the coupling of the valence proton particles with vibrations of the underlying Hg core induces a factor of two increase of the quadrupole moments.

High-spin states in 142Gd have been populated by means of the 99Ru(48Ti, 2p3n) reaction at 240 MeV and investigated with the γ-spectrometer EUROBALL III and the charged-particle detector array ISIS. The features of four dipole bands have been determined and compared with tilted-axis cranking model calculations indicating that they are magnetic rotational bands. A transition from regular to irregular bands has been found approaching N = 82 demonstrating that this is a general phenomenon in nuclei near a double-shell closure.

International audience; The level scheme of the nucleus Te-120, populated in the reaction Se-80(Ca-48, alpha 4n), was reinvestigated using gamma-ray coincidence data measured with the Gammasphere spectrometer. Previously, five high-spin rotational bands were discovered in this nucleus. The present reinvestigation revealed that the decay of band b1 is more complex than suggested in the earlier work and that it cannot be uniquely determined. Furthermore, a number of new transitions are added to the level scheme. The implications for the spin assignments and excitation energies of the five bands and for comparisons with cranked Nilsson-Strutinsky calculations are discussed.

The band structures built on the 5- isomeric state ( T 1/2 = 3.46 m) in the doubly odd 130Cs nucleus have been established up to I = 24? via the 124Sn(11B, 5n)130Cs reaction. The previously observed bands based on the πh 11/2⊗νh 11/2, πg 7/2⊗νh 11/2 and πd 5/2⊗νh 11/2 configurations and a positive-parity side band with multiple connections to the α = 0 signature partner of the yrast πh 11/2⊗νh 11/2 band have been extended to higher spins. A new band based on the πh 11/2⊗νg 7/2 configuration is observed. The yrast πh 11/2⊗νh 11/2 band exhibits anomalous signature splitting whose magnitude decreases up to spin 15 and then increases without restoring the normal signature splitting.

High-spin states in 197Pb and 198Pb were populated in the 186W(18O ,x n) reactions. In-beam γ -ray coincidences were measured in two experiments using the Gammasphere and the Eurogam II spectrometer arrays, respectively. In both nuclei new bands of enhanced magnetic dipole transitions were found and the known cascades were partly reordered and extended to higher spins. In most cases, γ -ray transitions connecting the magnetic rotational bands to lower-lying states have been identified. Configuration assignments are suggested for the bands. The systematic behavior confirms the shears mechanism. An effective interaction between the main high-spin proton and neutron orbitals is derived.

Lifetimes of states in at least one of the M1 bands in each nucleus from 193−197 Pb have been determined through Doppler-Shift Attenuation Method experiments performed with the Gammasphere array. The nuclei were populated under similar conditions allowing accurate relative measurements of the state lifetimes. The deduced B(M1) values display the characteristic decrease with increasing angular momentum which is a clear signature of the shears mechanism. Combined with the recent results for 198,199 Pb an impressive body of evidence now exists which supports the interpretation of these structures as examples of a new mode of nuclear behavior: `magnetic rotation'.

Excited states have been identified for the first time in 184Pb, the first even-even Pb isotope beyond the 82 < N < 126 mid-shell, using the recoil-decay tagging (RDT) technique. A collective band built on the first-excited 2+ state has been observed. This resembles those seen in 186,188Pb and the Hg isotones, and can thus be associated with a prolate-deformed shape. Variable moment of inertia (VMI) fits of the prolate 0+ level energies in 184,186,188Pb indicate that the minimum appears at N= 103, the same neutron number at which the corresponding minimum in Hg isotopes is observed.

The recently discovered regular bands of enhanced $M1$ $\ensuremath{\gamma}$-ray transitions in nearly spherical Pb nuclei have been explained in terms of magnetic rotation. However, the special angular momentum coupling of the nucleons that form magnetic-rotational states has never been tested experimentally. In this paper, we report on the measurement of the $g$ factor of the 2583-keV head of such a band in ${}^{193}\mathrm{Pb}$. The result, $g\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.68(3)$, is the first direct proof of the almost perpendicular coupling of the proton-particle and neutron-hole angular momentum vectors. This coupling results in a large component of the magnetic moment perpendicular to the total nuclear angular momentum, which is required for the occurrence of magnetic rotation.

Conference of 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 ; Conference Code:102802; International audience; For Homeland Security, enhanced detection and identification of radioactive sources and nuclear material has become of increasing importance. The scintilla project aims at minimizing the risk of radioactive sources dissemination especially with masked and shielded material. SCINTILLA offers the capacity to finding a reliable alternative to Helium-3 based detection systems since the gas which is predominantly used in nuclear safeguards and security applications has now become very expensive, rare and nearly unavailable. SCINTILLA benchmarks will be based on international standards. Radiation Portal testing being carried out at the Joint Research Centre (JRC) in Ispra (Italy).

High-spin states in I-123 were populated in the reaction Se-80(Ca-48,p4n)I-123 at a beam energy of 207 MeV and gamma-ray coincidence events were measured using the Gammasphere spectrometer. Three weakly populated, high-spin rotational bands have been discovered with characteristics similar to those of the long collective bands recently observed in other nuclei of this mass region. Configuration assignments are proposed based on calculations within the framework of the cranked Nilsson-Strutinsky approach. DOI: 10.1103/PhysRevC.86.067305

High-spin states in 197 Pb have been investigated by in-beam γ-ray spectroscopy. Two previously known high-spin magnetic-dipole sequences have been connected to the spherical level scheme at lower spins. A reordering of the transitions in the previously reported irregular band leads to a regular sequence with a band crossing. The properties of the dipole sequences are interpreted in terms of “shears bands” within the tilted-axis cranking model.

High-spin states in I-123 have been populated in the Se-80(Ca-48, p4n) I-123 reaction at 207 MeV and gamma-ray coincidence events have been recorded with the Gammasphere spectrometer. The level scheme of I-123 has been extended up to spin I = 63/2. The nucleus undergoes a shape transition from moderately deformed states with collective rotation at low spins to noncollective oblate configurations at higher spins. Maximally aligned terminating states involving all nine particles outside the Sn-114 core and states with one particle antialigned are identified. A large number of weak transitions feed the terminating states. Cranked Nilsson-Strutinsky calculations have been performed to determine possible configurations for the observed energy levels. (Less)

High-spin states in (120)Te were populated in the reaction (80)Se((48)Ca, alpha 4n)(120)Te at a beam energy of 207 MeV and gamma-ray coincidences were measured using the Gammasphere spectrometer. The previously known level scheme is extended to higher spin and new interband transitions and side-feeding branches are established. Five highly deformed rotational bands, extending up to almost I = 50, are observed for the first time. The bands are compared with similar structures found recently in neighboring nuclei. The experimental results are interpreted within the framework of the cranked Nilsson-Strutinsky model. Configuration assignments to several terminating states and to the high-spin bands are discussed.

The spectroscopic quadrupole moment of the ${T}_{1/2}=9.4(5)$ ns isomer in $^{193}\mathrm{Pb}$ at an excitation energy ${E}_{\mathrm{ex}}=(2585+x)$ keV is measured by the time-differential perturbed angular distribution method as $|{Q}_{s}|=2.6(3)$ $e$ b. Spin and parity ${I}^{\ensuremath{\pi}}=27/{2}^{\ensuremath{-}}$ are assigned to it based on angular distribution measurements. This state is the band head of a magnetic-rotational band, described by the $1{i}_{13/2}$ subshell with the $(3{s}_{1/2}^{\ensuremath{-}2}1{h}_{9/2}1{i}_{13/2}){}_{{11}^{\ensuremath{-}}}$ proton excitation. The pairing-plus-quadrupole tilted-axis cranking calculations reproduce the measured quadrupole moment with a moderate oblate deformation ${\ensuremath{\epsilon}}_{2}=\ensuremath{-}0.11$, similar to that of the ${11}^{\ensuremath{-}}$proton intruder states, which nuclei in the region. This is the first direct measurement of a quadrupole moment and thus of the deformation of a magnetic-rotational band head.

The location of nuclear closed shells, as evidenced through discontinuities in binding energy and one- and two-particle separation energy systematics, remains one of the simplest tests of global nuclear models. How shell gaps evolve, whether with increasing mass, increasing neutron:proton ratio or increasing deformation, is still uncertain, and it has recently been suggested that one must go beyond a static meanfield picture to include the effects of dynamic fluctuations in the nuclear shape even in the ground state. The identification of key properties which may distinguish between competing approaches is thus vital. Comparison of the binding energies of superdeformed nuclei in the A ≈ 190 region shows that two-proton separation energies are higher in the superdeformed state than in the normal state, despite the probably lower Coulomb barrier and lower total binding energy. Possible reasons for this difference are discussed. This somewhat counterintuitive result provides a critical test for global nuclear models.

The $g$ factors of the ${12}^{+}$, ${11}^{\ensuremath{-}}$, and ${8}^{\ensuremath{-}}$ isomeric states in $^{188}\mathrm{Pb}$ were measured using the time-differential perturbed angular distribution method as $g({12}^{+})=\ensuremath{-}0.179(6)$, $g({11}^{\ensuremath{-}})=+1.03(3)$, and $g({8}^{\ensuremath{-}})=\ensuremath{-}0.037(7)$. The $g$ factor of the ${12}^{+}$ state follows the observed slight down-sloping evolution of the $g$ factors of the ${i}_{13/2}^{2}$ neutron spherical states with decreasing $N$. The $g$ factors of the ${11}^{\ensuremath{-}}$ and ${8}^{\ensuremath{-}}$ isomers proposed as oblate and prolate deformed states, respectively, were interpreted within the rotational model, using calculated and empirical $g$ factor values for the involved single-particle orbitals.

A measurement of the energy and spin of superdeformed states in {sup 190}Hg, obtained through the observation of transitions directly linking superdeformed and normal states, expands the number of isotopes in which binding energies at superdeformation are known. Comparison with neighboring nuclei shows that two-proton separation energies are higher in the superdeformed state than in the normal state, despite the lower Coulomb barrier and lower total binding energy. This unexpected result provides a critical test for nuclear models.

The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV $\ensuremath I^{\pi}=12^+$ isomer in 192Pb with $ \tau$ = 1.57 μs has been produced using the fragmentation of a 1A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, $ \tau$ = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.

For a level scheme investigation of ^{142}Gd an experiment with the $\gamma$-spectrometer EUROBALLIII has been carried out and lifetimes have been measured with EUROBALL IV using the Doppler-shift attenuation method. The high-spin states have been populated in these experiments by means of the ^{99}Ru(^{48}Ti, 2p3n) reaction at a beam energy of 240MeV and the ^{114}Sn(^{32}S, 2p2n) reaction at 160MeV, respectively. Reduced E2 transition probabilities B(E2) were determined for 15 members of four quadrupole bands. For the interpretation of the positive-parity even-spin quadrupole bands, calculations in the cranked Nilsson-Strutinsky as well as interacting boson models have been performed. From the former calculations it was concluded that the high-spin states of the (+ , 0)_{1} band in ^{142}Gd represent a triaxial nucleus rotating around the longest principal axis.

Lifetimes have been measured for a dipole band in 139Sm using DSAM. The deduced B(M1) and B(E2) values as well as B(M1)/B(E2) ratios are compared with calculations in the framework of the TAC (Tilted Axis Cranking) and SPAC (Shears mechanism with Principal Axis Cranking) models. The dipole band in 139Sm can be considered as a magnetic rotational band with a prolate or triaxial nuclear deformation.

Tilt angles, deformation parameters, angular momenta, and reduced magnetic dipole and electric quadrupole transition probabilities are calculated within the framework of the tilted-axis cranking model for shears bands in the neutron-deficient Pb isotopes {sup 193}Pb to {sup 202}Pb. The self-consistently calculated quadrupole-deformation parameters for the various configurations lie around {epsilon}{sub 2}=-0.1, and the triaxiality is small. The tilt angle, i.e., the angle between the angular momentum and the nuclear symmetry axis, remains almost constant within each band, showing only a small increase toward higher angular momenta. The angular momentum increases mainly due to the shears effect, which is a step-by-step alignment of high-j proton and neutron orbitals into the direction of the total angular momentum. Calculated and experimental M1 transition rates are in good agreement. They decrease with increasing spin within the bands as expected for the shears effect. The calculated B(E2) values show only a weak spin dependence. However, the experimental B(E2) values have large errors, and more accurate data are needed to decide between the present model and a recently suggested geometrical approach.

Spectroscopic quadrupole moment measurements for high‐spin isomeric states in 192,193,194Pb nuclei have been performed by the time‐differential perturbed γ‐ray angular distribution method. The quadrupole moments of the isomers described by quasineutron configurations in neutron‐deficient Pb nuclei are well reproduced by the pairing plus quadrupole model, which predicts for these states a very small prolate deformation β2 ≈0.02. The quadrupole moment of the 11− isomeric state in 192Pb involving the π(3s1/2−2 1h9/2 1i13/2) configuration corresponds to a deformation β2=−0.11(1). The quadrupole moments of the proton intruder states in Pb nuclei are compared with theoretical predictions of tilted‐axis cranking, mean‐field and interacting boson models.

For a level scheme investigation of 142Gd an experiment with the γ -spectrometer EUROBALLIII has been carried out and lifetimes have been measured with EUROBALL IV using the Doppler-shift attenuation method. The high-spin states have been populated in these experiments by means of the 99Ru(48Ti, 2p3n) reaction at a beam energy of 240MeV and the 114Sn(32S, 2p2n) reaction at 160MeV, respectively. Reduced E2 transition probabilities B(E2) were determined for 15 members of four quadrupole bands. For the interpretation of the positive-parity even-spin quadrupole bands, calculations in the cranked Nilsson-Strutinsky as well as interacting boson models have been performed. From the former calculations it was concluded that the high-spin states of the (+ , 0)1 band in 142Gd represent a triaxial nucleus rotating around the longest principal axis.

The g factors and quadrupole moments of the 21/2{sup -} and 33/2{sup +} isomers in {sup 193}Pb have been measured by the time-differential perturbed {gamma}-ray angular distribution method as g(21/2{sup -})=-0.059(11), |Q(21/2{sup -})|=0.22(2) eb and g(33/2{sup +})=-0.171(9), |Q(33/2{sup +})|=0.45(4) eb. The results support the three-neutron configurations (1i{sub 13/2}){sub 12{sup +}}{sup 2}x3p{sub 3/2} and (1i{sub 13/2}){sup 3} for the 21/2{sup -} and 33/2{sup +} states, respectively. The quadrupole moment of the 12{sup +} isomer in {sup 194}Pb described by the two-neutron (1i{sub 13/2}){sup 2} configuration has been remeasured as |Q(12{sup +})|=0.48(3) eb in perfect agreement with the previous data. The experimental results are discussed within a microscopic Bardeen-Cooper-Schrieffer approach in a number-projected one- and three-quasiparticle neutron space, and in the frame of the pairing plus quadrupole tilted-axis cranking model.

The quadrupole moment of the 11 isomer in 1 9 6 Pb has been measured by the level mixing spectroscopy method. This state has a π(3s - 2 1 / 2 1h 9 / 2 1i 1 3 / 2 )11 - configuration which is involved in most of the shears band heads in the Pb region. The first directly measured value of Q s (11 - ) = (-)3.41(66) b, coupled to the previously known quadrupole moment of the ν(1i - 2 1 3 / 2 )12 + isomer allows us to estimate the quadrupole moment of the 16 - shears band head as Q s (16 - ) = -0.32(10) b. The experimental values are compared to tilted axis cranking calculations, giving insight into the validity of the additivity approach to couple quadrupole moments and on the amount of deformation in the shears bands.

The spectroscopic quadrupole moments of the 11− isomers in 194Pb and 196Pb have been measured by applying the Level Mixing Spectroscopy technique. These isomers have the π(s1/2−2h9/2i13/2) proton configuration. The implications of these results for the influence of the intruder character of the isomers on their deformation is given. We will especially focus on a simple 2-dimensional model, taking into account the coupling of the valence nucleons with the vibrations of the underlying core, which gives theoretical insight in the obtained experimental results for the quadrupole moments of the 11− isomers.

Lifetimes for low-lying members of the irregular ΔI = 1 band in 196Pb have been measured by means of the EUROBALL spectrometer using the coincidence recoil distance technique. The 164Dy(36S,4n)196Pb reaction at a beam energy of 168 MeV was used. The data were analyzed with the differential decay-curve method (DDCM). A characteristic drop in the reduced transition probabilities with increasing angular momentum was observed in agreement with predictions by the semiclassical model for the shears mechanism.

Three mini-orange conversion–electron spectrometers and four Euroball Ge Cluster detectors have been used for γ–e- coincidence spectroscopy of superdeformed 135Nd. Transitions within the superdeformed band are shown to have the expected E2 multipolarity. The 766.5–keV transition which links the band to a positive-parity state has a conversion coefficient consistent with M1 multipolarity. Consequently, positive parity is deduced for the superdeformed band. No evidence for E0 transitions was found.

In nuclei in the mass region around A = 190-200 a large number of regular dipole sequences have recently been found. In these bands the gain in angular momentum may not be created by collective rotation as is usual for more deformed nuclei, but stems from aligning the proton and neutron spins in the direction of the total spin axis. Calculations within the frame-work of the tilted axis cranking model reproduce the available experimental data and support the alignment picture.

High-spin states in 201 Pb and 202 Pb have been investigated using in-beam γ-ray spectroscopic techniques. Seven regular sequences of enhanced dipole transitions, with weak E2 crossovers in some cases, have been found, one of which is firmly connected to low-lying levels in 201 Pb. These bands are interpreted to be built on high-spin proton-particle neutron-hole excitations. Tilted-axis cranking calculations show that the angular momentum along the bands is predominantly generated by a continuous and simultaneous reorientation of the proton and neutron spins into the direction of the total angular momentum (shears effect).

The quadrupole interaction of high-spin isomers in 193Pb implanted into solid Hg cooled at a temperature T = 170 K has been investigated by the time-differential perturbed $\gamma$ -ray angular-distribution method. Spectroscopic quadrupole moment values of $\vert Q_{\rm s} \vert = 0.22(2)$ eb and 0.45(4) eb have been deduced for the 21/2- and 33/2 + three-neutron states, respectively. A much higher value $\vert Q_{\rm s} \vert = 2.84(26)$ eb has been determined for the 29/2- isomer, the band head of a magnetic rotational band.

We have investigated the structure of the superdeformed band in 135Nd using conversion-electron spectroscopy. The transitions within the superdeformed band show conversion coefficients which are consistent with an E2 multipolarity. From the conversion coefficients of transitions linking this band with known low-lying states its positive parity was established. Hence, a direct determination of the parity of a high-spin superdeformed band could be performed for the first time.

High-spin states in 202Pb and 203Pb have been investigated by in-beam γ-ray spectroscopy following the reaction 198Pt(9Be,xn). A search for magnetic rotational bands in these isotopes confirmed one of the two bands previously assigned to 202Pb and revealed a new band in this isotope. No evidence for magnetic rotation has been found in 203Pb.

High-spin states in 196 Pb have been populated in two different heavy-ion-induced reactions using thin and Au-backed targets, respectively. Gamma-ray coincidences were measured using the EUROBALL spectrometer array. Five new magnetic-rotational bands have been found. The previously known four bands have been extended and some of their levels have been reordered. With one exception, all the bands have been connected to lower-lying states and excitation energies, spins and parities have been determined. From the systematic properties of the bands and from comparison to tilted-axis cranking calculations, arguments for configuration assignments to the bands are derived. It is suggested that the bands are based on proton 11 − and 8 + particle states coupled to various neutron–hole excitations.

A detailed spectroscopic study of high‐spin states in 196Pb has been carried out using the EUROBALL spectrometer array. Five new magnetic‐rotational bands have been found and the previously known bands have been extended. With one exception, all the bands have been connected to lower‐lying states and excitation energies, spins and parities have been determined. Doppler‐broadend lineshapes have been analyzed and lifetimes of states in four of the bands have been determined. The B(M1) values show the decrease with increasing spin that is expected for shears bands. Configurations of proton‐particle excitations coupled to neutron‐hole states have been assigned to the bands.