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Lifetimes of yrast and nonyrast states of 102Pd populated via the 92Zr( 13C, 3n) reaction are measured by means of the recoil distance Doppler-shift technique with a Cologne plunger coupled to a GASP spectrometer. The event-by-event data accumulated at 24 plunger distances in the range of 0.1 μm to 9 mm are analyzed using the differential decay curve method. The resulting B(E2) values of the γ transitions depopulating yrast-band members up to the I π = 8+ state are found to deviate significantly from the corresponding predictions of the E(5) critical-point symmetry. [ABSTRACT FROM AUTHOR]

Odd-odd 138La nuclei have been produced in the 12C+238U fusion-fission reaction and their γ rays studied with the Euroball array. The high-spin level scheme has been built up to ~4.5 MeV excitation energy and spin I~16h from the triple γ-ray coincidence data. An isomeric state lying at 739-keV excitation energy has been identified. The configurations of the structures are first discussed by analogy with the proton excitations identified in the semimagic 139La82 nucleus, which involve the three high-j orbits lying above the Z=50 gap, pg7/2, pd5/2, and ph11/2. The competition of these three orbits to produce the yrast line is confirmed by the results of shell-model calculations performed in this work. [ABSTRACT FROM AUTHOR]

The nucleus 100Ru appears to be a good candidate for the E(5) critical point symmetry which describes the U(5)-SO(6) shape phase transition. To investigate this point with respect to the electromagnetic transition strengths, lifetime measurements of its yrast states have been performed using the recoil distance Doppler shift technique as well as the Doppler shift attenuation method. As a result, the lifetimes of the yrast 2+, 4+, and 8+ states were determined. The deduced transition strengths are compared to the E(5) predictions as well as to the results of excited Vampir and shell-model calculations. [ABSTRACT FROM AUTHOR]

Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich N = 52 isotones 88Kr and 86Se were investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at GANIL (Caen, France) using the Orsay Universal Plunger System (OUPS) for the RDDS technique and the AGATA array for the γ-ray detection coupled to the VAMOS++ magnetic spectrometer for an event-by-event particle identification. In 88Kr, the lifetimes of seven levels were determined and in 86Se, the lifetimes of five levels were determined. The deduced B(E2; 2+1℥ 0+1) are compared with mean-field and shellmodel calculations. [ABSTRACT FROM AUTHOR]

We have recently successfully demonstrated a new technique for production and study of many of the most exotic neutron-rich nuclei at moderate spins. LICORNE, a newly developed directional inverse-kinematic fast neutron source at the IPN Orsay, was coupled to the MINIBALL high resolution γ-ray spectrometer to study nuclei the furthest from stability using the 238U(n, ƒ) reaction. This reaction and 232Th(n, ƒ) are the most neutron-rich fission production mechanisms achievable and can be used to simultaneously populate hundreds of neutron-rich nuclei up to spins of ~ 16 h. High selectivity in the experiment was achieved via triple γ-ray coincidences and the use of a 400 ns period pulsed neutron beam, a technique which is unavailable to other population mechanisms such as 235U(nth, ƒ) and 252Cf(SF). The pulsing allows time correlations to be exploited to separate delayed γ rays from isomeric states in the hundreds of nuclei produced, which are then used to cleanly select a particular nucleus and its exotic binary partners. In the recent experiment, several physics cases are simultaneously addressed such as shape coexistence, the evolution of shell closures far from stability, and the spectroscopy of nuclei in the r-process path near N = 82. Preliminary physics results on anomalies in the 238U(n, ƒ) fission yields and the structure of the 138Te and 100Sr nuclei will soon be published. A future project, v-ball, to couple LICORNE with a hybrid escape-suppressed spectrometer to refine further the technique and achieve a large increase in the observational limit is discussed. [ABSTRACT FROM AUTHOR]

For certain combinations of protons and neutrons in atomic nuclei, a rise of a reflection asymmetry is expected. Experimental E3 strengths, which as a function of the neutron number peak at around N ≈ 88 and N ≈ 134, indicate enhanced octupole correlations as predicted by theory. Low-energy Coulomb excitation is a highly successful method for establishing the evolution of nuclear shapes, through the measurement of cross sections, to populate excited states that can be directly related to the static and dynamic moments of the charge distribution of the nucleus. A Coulomb excitation experiment at the ALTO facility, Orsay was performed recently to study collective properties of 146Nd and 148Sm. In particular, the strengths of the <3-∣∣E3∣∣0+> and <1-∣∣E3∣∣4+> matrix elements will provide a clear distinction between octupole vibration and rigid deformation. [ABSTRACT FROM AUTHOR]

High-spin states in 139Ce have been populated using the 130Te(14C,5n) reaction. The level scheme has been extended to higher spins, including a new band of dipole transitions. The parity of several states has been changed from negative to positive, mainly based on the comparison with the level structure of the core nucleus 140Ce and the results of a realistic shell-model calculation. The dipole band is interpreted as a magnetic rotation band with πh11/2² ⊗ νh-111/2 configuration built on small deformation axial shape with (ɛ2 = 0.12,γ = 0°). [ABSTRACT FROM AUTHOR]

It is pointed out that the triaxial bands in 138-140Nd and in the Lu/Er nuclei can be understood from the same shell structure effects. Two of the bands in 138Nd, interpreted as signature partners, exhibit a crossing at high spins with a signature splitting which is strongly reduced above the crossing. This behavior is unique among the yrast and close-to-yrast configurations, revealing the mechanism which induces a change of the rotation axis from short to intermediate in the triaxially deformed nucleus. [ABSTRACT FROM AUTHOR]

The population of the high-spin states in 140Nd was investigated using the reaction 96Zr(48Ca,4n). The results from two experiments, one with the EUROBALL array and one with the JUROGAM II+RITU+GREAT setup employing the recoil decay tagging technique, have been combined to develop a very detailed level scheme for 140Nd. Twelve bands of quadrupole transitions and eleven bands of dipole transitions were identified and their connections to low-lying states were established. Calculations using the cranked Nilsson-Strutinsky and the tilted axis cranking models were used to interpret the observed structures. The overall good agreement between the experimental results and the calculations assuming a triaxial shape of the nucleus strongly support the existence of a stable triaxial shape at high spins in this mass region. [ABSTRACT FROM AUTHOR]

Background: Astrophysical models studying the origin of the neutron-deficient ρ nuclides require knowledge of proton capture cross sections at low energy. The production site of the ρ nuclei is still under discussion but a firm basis of nuclear reaction rates is required to address the astrophysical uncertainties. Data at astrophysically relevant interaction energies are scarce. Problems with the prediction of charged particle capture cross sections at low energy were found in the comparisons between previous data and calculations in the Hauser-Feshbach statistical model of compound reactions. Purpose: A measurement of 74Ge(p, y)75As at low proton energies, inside the astrophysically relevant energy region, is important in several respects. The reaction is directly important because it is a bottleneck in the reaction flow which produces the lightest ρ nucleus 74Se. It is also an important addition to the data set required to test reaction-rate predictions and to allow an improvement in the global ρ + nucleus optical potential required in such calculations. Method: An in-beam experiment was performed, making it possible to measure in the range 2.1 ≤ Ep ≤3.7 MeV, which is for the most part inside the astrophysically relevant energy window. Angular distributions of the )/-ray transitions were measured with high-purity germanium detectors at eight angles relative to the beam axis. In addition to the total cross sections, partial cross sections for the direct population of 12 levels were determined. Results: The resulting cross sections were compared to Hauser-Feshbach calculations using the code SMARAGD. Only a constant renormalization factor of the calculated proton widths allowed a good reproduction of both total and partial cross sections. The accuracy of the calculation made it possible to check the spin assignment of some states in75 As. In the case of the 1075-keV state, a double state with spins and parities of 3/2- and 5/2- is needed to explain the experimental partial cross sections. A change in parity from 5/2+ to 5/2- is required for the state at 401 keV. Furthermore, in the case of 74Ge, studying the combination of total and partial cross sections made it possible to test the γ width, which is essential in the calculation of the astrophysical 74As(n,?)75As rate. Conclusions: Between data and statistical model prediction a factor of about two was found. Nevertheless, the improved astrophysical reaction rate of 74Ge(/?, γ) (and its reverse reaction) is only 28% larger than the previous standard rate. The prediction of the 74As(n,y)75As rate (and its reverse) was confirmed, the newly calculated rate differs only by a few percent from the previous prediction. The in-beam method with high-efficiency detectors proved to be a powerful tool for studies in nuclear astrophysics and nuclear structure. [ABSTRACT FROM AUTHOR]

The nuclear level density and the &ggr;-ray strength function have been determined for 43Sc in the energy range up to 2 MeV below the neutron separation energy using the Oslo method with the 46Ti(p, &agr;)43Sc reaction. A comparison to 45Sc shows that the level density of 43Sc is smaller by an approximately constant factor of two. This behavior is well reproduced in a microscopic, combinatorial model calculation. The &ggr;-ray strength function increases at low &ggr;-ray energies, a feature which has been observed in several nuclei but which still awaits theoretical explanation. [ABSTRACT FROM AUTHOR]

Primary &ggr;-ray spectra for a wide excitation-energy range have been extracted for 44Ti from particle-y coincidence data of the 46Ti(p,t&ggr;)44Ti reaction. These spectra reveal information on the &ggr;-decay pattern of the nucleus and may be used to extract the level density and radiative strength function applying the Oslo method. Models of the level density and radiative strength function are used as input for cross-section calculations of the 40Ca(&agr;,&ggr;)44Ti reaction. Acceptable models should reproduce data on the 40Ca(&agr;,&ggr;)44Ti reaction cross section as well as the measured primary &ggr;-ray spectra. This is only achieved when a coherent normalization of the slope of the level density and radiative strength function is performed. Thus, the overall shape of the experimental primary &ggr;-ray spectra puts a constraint on the input models for the rate calculations. [ABSTRACT FROM AUTHOR]

Abstract: Differential cross-section measurements of the 6Li(d,α0)4He reaction have been performed for deuteron energy between 900 and 2000keV in steps of 25keV. The reaction α particles were detected at four backward angles from 140° to 170° in steps of 10°. A qualitative discussion of the observed variations in the reaction cross sections through the influence of resonances in the d+ 6Li compound system is presented. The results are also compared to existing data, when present, and are validated through benchmarking experiments using high-purity, thick, mirror-polished natural LiF and LiAlO2 targets. [Copyright &y& Elsevier]

Abstract: In the present study the differential cross sections of the 45Sc(p,p)45Sc reaction were measured. Two independent experiments were performed. At first a sandwiched thin ScBr3 target was used for beam energies E LAB =2300–5500keV (in steps of 25 and 50keV) and for detector angles 140°, 160°, and 170°. Secondly a thick Sc2O3 sample was formed and irradiated for E LAB =3100–5500keV with a detector placed at 140°, to validate the results of the first measurement. [Copyright &y& Elsevier]

Particle-γ coincidences from the 46Ti(p,p'γ)46Ti inelastic scattering reaction with 15-MeV protons are utilized to obtain γ-ray spectra as a function of excitation energy. The rich data set allows analyzsis of the coincidence data with various gates on excitation energy. For many independent data sets, this enables a simultaneous extraction of level density and radiative strength function (RSF). The results are consistent with one common level density. The data seem to exhibit a universal RSF as the deduced RSFs from different excitation energies show only small fluctuations provided that only excitation energies above 3 MeV are taken into account. If transitions to well-separated low-energy levels are included, the deduced RSF may change by a factor of 2-3, which might be expected because of the involved Porter-Thomas fluctuations. [ABSTRACT FROM AUTHOR]