56152487
Rotation and shape changes in 151Tb and 196Pb: Probes of nuclear structure and tunneling process in warm nuclei. I. Experimental analysis
The {gamma} decay associated with the warm rotation of the superdeformed nuclei {sup 151}Tb and {sup 196}Pb has been measured with the Euroball IV array. Several experimental quantities are presented, putting strong constraints on the decay dynamics in the superdeformed well. The data are successfully reproduced using a Monte Carlo simulation of the {gamma} decay based on microscopically calculated energy levels, E2 decay probabilities, collective mass parameters, and potential energy barriers between the wells associated with normal and super deformation. This allows one to test the basic ingredients of the physical process, such as the strength of the two-body residual interaction and the potential barriers as a function of spin and excitation energy. We also show that the data probe the E1 strength function, indicating an enhancement around 1-2 MeV {gamma} rays, which might be related to octupole vibrations.
122653467
Fusion of 28Si + 28Si: oscillations above the barrier and the behavior down to 1μb
Fusion excitation functions of light heavy-ion systems show oscillatory struc- tures above the Coulomb barrier, caused by resonances or due to the penetration of suc- cessive centrifugal barriers well separated in energy. In heavier systems, the amplitude of oscillations decreases and the peaks get nearer to each other. This makes the measure- ments very challenging. We have performed a first experiment for 28 Si + 28 Si, by measuring fusion cross sections ( ) in an energy range of'15 MeV above the barrier, with a small Elab = 0.5 MeV step. Three regular oscillations are clearly observed, which are best revealed by plotting the energy-weighted derivative of the excitation function. The excitation function has been recently measured down to cross sections 1 b with larger energy steps. Coupled-channel (CC) calculations based on a shallow potential in the entrance channel are able to reproduce the oscillations. A further analysis will provide a stringent test for the calculations, in particular for the choice of the ion-ion potential, because the sub- barrier excitation function has to be reproduced as well.
53654548
gamma spectroscopy of calcium nuclei around doubly magic Ca-48 using heavy-ion transfer reactions
This work was supported by the Italian Istituto Nazionale di Fisica Nucleare and partially by the Spanish MICINN (AIC10-D-000568 bilateral action and FPA2008-06419) and Generalitat Valenciana (Grant PROMETEO/2010/101). The work has also been partially supported by the Polish Ministry of Science and Higher Education (Grant No. N N202 309135)
17188150
The Population of Metastable States as a Probe of Relativistic-energy Fragmentation Reactions
Isomeric ratios have been measured for high-spin states in Po-198,200,206,208(84), At-208,209,210,211(85), Rn-210,211,212,213,214(86), Fr-208,211,212,213,214(87), Ra-210,211,212,214,215(88), and Ac-215(89) following the projectile fragmentation of a 1 AGeV U-238 beam by a Be-9 target at GSI Helmholtzzentrum fur Schwerionenforschung. The fragments were separated in the fragment separator (FRS) and identified by means of energy loss and time-of-flight techniques. They were brought to rest at the centre of the RISING gamma-ray detector array and intensities of gamma rays emitted in the decay of isomeric states with half-lives between 100 ns and 40 mu s and spin values up to 55/2 (h) over bar were used to obtain the corresponding isomeric ratios. The data are compared to theoretical isomeric ratios calculated in the framework of the abrasion-ablation model. Large experimental enhancements are obtained for high-spin isomers in comparison to expected values. (C) 2013 Elsevier B.V. All rights reserved. (Less)
5034444
Study of the multi-nucleon transfer reactions of 136Xe + 198Pt for producing exotic heavy nuclei
The feasibility of the multi-nucleon transfer (MNT) reaction in the 136 Xe + 198 Pt system was investigated for synthesizing neutron-rich heavy nuclei around mass number A 200 of astrophysical interest. Identification of the projectile-like fragments (PLF's) was successfully performed by using VAMOS++ spectrometer. The isotopic distributions of the PLF's produced by two-proton stripping and pickup reactions were compared with each other, demonstrating the properties of the MNT reactions observed in the present system. The two-proton pickup channels strongly populated than the two- proton stripping channels were observed. The isotopic distributions for di erent total kinetic energy loss (TKEL) ranges are also discussed. The overall enhancement of the strength of the two-proton pickup compared with the two-proton stripping appears to be related to the MNT reactions with relatively moderate energy dissipation.
121575889
Lifetime Measurements of the Neutron-Rich N=30 Isotones Ca-50 and Sc-51: Orbital Dependence of Effective Charges in the fp Shell
The lifetimes of the first excited states of the N=30 isotones Ca-50 and Sc-51 have been determined using the Recoil Distance Doppler Shift method in combination with the CLARA-PRISMA spectrometers. This is the first time such a method is applied to measure lifetimes of neutron-rich nuclei populated via a multinucleon transfer reaction. This extends the lifetime knowledge beyond the f(7/2) shell closure and allows us to derive the effective proton and neutron charges in the fp shell near the doubly magic nucleus Ca-48, using large-scale, shell-model calculations. These results indicate an orbital dependence of the core polarization along the fp shell.
8924046
Borexino calibrations: Hardware, Methods, and Results
Borexino was the first experiment to detect solar neutrinos in real-time in the sub-MeV region. In order to achieve high precision in the determination of neutrino rates, the detector design includes an internal and an external calibration system. This paper describes both calibration systems and the calibration campaigns that were carried out in the period between 2008 and 2011. We discuss some of the results and show that the calibration procedures preserved the radiopurity of the scintillator. The calibrations provided a detailed understanding of the detector response and led to a significant reduction of the systematic uncertainties in the Borexino measurements.