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In this work we estimate the production rates for the three-body radiative capture processes α + n + n → He + γ and α + α + n → Be + γ, as well as the four-body recombination reactions α + α + n + n → He + α, + n + n + n → He + n, α + α + n + n → Be + n and α + α + α + n → Be + α. These processes compete as a source of He and Be. The hyperspherical adiabatic expansion method is used. With this method no assumption is made about the capture mechanism. Both sequential and direct capture are included. The production rates for the radiative and the four-body recombination processes are found to be comparable for a mass density of about 10g/cm ( ∼ 10 neutrons/cm) and temperatures of a few GK. [ABSTRACT FROM AUTHOR]

The $ \beta^{{+}}_{}$ /EC decay of 185Tl was studied at the ISOLDE facility, the $ \gamma$ -rays belonging to 185Hg have been identified and a partial low-spin level scheme of 185Hg has been built. The decay of 185m+gHg was studied at the ISOCELE facility. Conversion electron lines of very low-energy transitions were observed for the first time. Electron data have been obtained for four transitions in 185Au and two transitions in 185Hg . From the analysis performed using an internal energy calibration procedure the energy location of the 185mHg has been determined to be $ E_{IS}= 103.7(4)$ keV. This $ E_{IS}$ value is consistent with that determined independently, $ E_{IS}=94(13)$ keV, using 185m+gHg $ \alpha$ -decay data from literature. New $ \alpha$ particles emitted from 189m+gPb have been detected and their origins determined by in-source laser spectroscopy at the ISOLDE facility. $ \alpha$ - $ \gamma$ coincidence results have served to locate the $ 13/2^{+}$ isomeric state of 189Pb at $ E_{IS}=40(4)$ keV. This latter $ E_{IS}$ value added to $ \alpha$ -decay data from literature have allowed the energy location of the $ 13/2^{+}$ isomeric states of 193Po and 197Rn at 95(7)keV and 194(12)keV, respectively. The nuclear structure of the isomeric and ground states in the nuclei of the three $ \alpha$ -emitter chains starting with 195m+g, 197m+g, 199m+gRn are discussed. [ABSTRACT FROM AUTHOR]

The electroproduction of charged $ \rho$ -mesons on the nucleon at intermediate energy is discussed for quasi-elastic kinematics. It is shown that at these kinematics both the longitudinal $ \sigma_{{L}}^{}$ and transverse $ \sigma_{{T}}^{}$ cross-sections are dominated by the $ \rho$ -meson t -pole contribution, and thus the corresponding dσ L( T)/d t data can give a valuable information on the $ \rho$ -meson component of the nucleon cloud. The differential cross-sections for the reaction p( e, e′ $ \rho^{+}_{}$) n at Q2 = 2 , 3.5GeV^2 and at the invariant mass W = 3 and 4GeV are calculated on the basis of quasi-elastic knockout mechanism with form factors. Questions about the gauge invariance of the electroproduction amplitude are considered and it is noted an important difference between photo- and electroproduction amplitudes. [ABSTRACT FROM AUTHOR]

We investigate to what extent 18Ne can be descibed as a three-body system made of an inert 16O core and two protons. We compare to experimental data and occasionally to shell model results. We obtain three-body wave functions with the hyperspherical adiabatic expansion method. We study the spectrum of 18Ne , the structure of the different states and the predominant transition strengths. Two 0+, two 2+, and one 4+ bound states are found where they are all known experimentally. Also one 3+ close to threshold is found and several negative-parity states, 1-, 3-, 0-, 2-, most of them bound with respect to the 16O excited 3- state. The structures are extracted as partial-wave components, as spatial sizes of matter and charge, and as probability distributions. Electromagnetic decay rates are calculated for these states. The dominating decay mode for the bound states is E2 and occasionally also M1 . [ABSTRACT FROM AUTHOR]

A UC target material of 11.3±0.5 g/cm^3 uranium density with the grain size of 20 and 5μm manufactured in a form of pills by the method of powder metallurgy has been tested on-line within the temperature range of 1800-2100 ° C . The mass of uranium exposed to the beam was 4-7g. The yields and release rates of Cs and Fr isotopes produced by fission and spallation reactions of 238U by 1GeV protons have been measured. The yields of Cs and Fr isotopes obtained from the tested target materials have been compared, including yields of very short-lived Fr isotopes with half-lives down to 1ms. Temperature-resistant materials (porous graphite and tantalum foil) have been used for the internal-container construction, which holds the UC target pills inside a tungsten external container heated by the resistant heating. The fastest release and the highest efficiency for short-lived isotopes have been obtained for the targets with the internal container manufactured from the tantalum foil. Results of on-line tests of a big mass target (730g of 5μm grain UC target material) have been discussed. [ABSTRACT FROM AUTHOR]

Isotope shifts and hyperfine splitting parameters have been measured for the neutron-deficient odd-mass lead isotopes 183-189Pb . The measurement was performed at the ISOLDE (CERN) online mass separator using the in-source resonance ionization spectroscopy technique. The nuclear root mean square charge radii 〈 r2〉 and the electromagnetic moments μ and QS have been deduced. They follow the smooth trend of the heavier isotopes and indicate the absence of deformation. [ABSTRACT FROM AUTHOR]

The $ \beta^{{+}}_{}$ /EC decay of 189m, gPb has been studied at the ISOLDE facility using nuclear spectroscopy and in-source laser spectroscopy. A level scheme of 189Tl has been built from $ \gamma$ - $ \gamma$ coincidence relationships and information on the feeding of some excited levels of 189Tl provided by the hyperfine spectra obtained from laser ionization. The half-lives of both the 13/2+ and 3/2- 189Pb isomers have been estimated to be T1/2 = 50±3 s and T1/2 = 39±8 s, respectively. Calculations have been performed for different oblate and prolate nuclear deformations using an axial-rotor coupled to one-quasiparticle model, a structure has been suggested for the low-lying levels of the 189Tl nucleus. [ABSTRACT FROM AUTHOR]

In this paper we present for the first time the measured delayed neutron (DN) yields and time spectra from high-energy protons interacting with thick natPb targets. The 1GeV protons from the accelerator impinged on targets of different thicknesses producing a huge number of spallation-fission products, some of which can be DN precursors. After the beam is switched off, the DNs were detected with optimized 3He counter. The production yields of light DN precursors as 17N and “usual” fission products as 87Br and 88Br, which dominate the total DN activity, are obtained both for thin and thick targets. These new data are of great interest for the new generation high-power spallation targets based on liquid-metal technologies. Our findings also should help to constrain the physics models within the simulations codes. [ABSTRACT FROM AUTHOR]

The hyperspherical adiabatic expansion is combined with complex scaling and used to calculate low-lying nuclear resonances of 12C in the 3 α model. We use Ali-Bodmer potentials and compare results for other potentials α- α with similar 8Be properties. A three-body potential is used to adjust the 12C resonance positions to desired values extending the applicability of the method to many-body systems decaying into three α-particles. For natural choices of three-body potentials we find 14 resonances below the proton separation threshold, i.e. two 0+, three 2+, two 4+, one of each of 1±, 2-, 3±, 4-, and 6+. The partial-wave decomposition of each resonance is calculated as a function of the hyperradius. Strong variation is found from small to large distance. The connection to previous experimental and theoretical results is discussed and agreements as well as disagreements are emphasized. [ABSTRACT FROM AUTHOR]

A new version of integrated target-ion source unit (ionising target) has been developed for the on-line production of radioactive single-charged ions. The target is able to withstand temperatures up to 2500 °C and acts also as an ion source of the surface and laser ionisation. Off-line and on-line experiments with the ionising target, housing tantalum foils as a target material, have been carried out at the IRIS (Investigation of Radioactive Isotopes on Synchrocyclotron) facility. The off-line surface ionisation efficiency measured for stable atoms of Li, Rb and Cs was correspondingly 6% , 40% and 55% at the target temperature of 2000 °C and 3-10% for atoms of rare-earth elements Sm, Eu, Tm and Yb at a temperature of 2200 °C. The off-line measured values of the ionisation efficiency for stable Gd and Eu atoms by the laser beam ionisation inside the target were 1% and 7%, respectively. The radioactive beam intensities of neutron-deficient rare-earth nuclides from Eu to Lu produced by the integrated target-ion source unit have been measured at a temperature of 2500 °C. The results of the integrated target-ion source unit use for on-line laser resonance ionisation spectroscopy study of neutron-deficient Gd isotopes have been also presented. [ABSTRACT FROM AUTHOR]

We expose the relation between the properties of the three-body continuum states and their two-body subsystems. These properties refer to their bound and virtual states and resonances, all defined as poles of the S-matrix. For one infinitely heavy core and two non-interacting light particles, the complex energies of the three-body poles are the sum of the two two-body complex pole-energies. These generic relations are modified by center-of-mass effects which alone can produce a Borromean system. We show how the three-body states evolve in 6He, 6Li, and 6Be when the nucleon-nucleon interaction is continuously switched on. The schematic model is able to reproduce the main properties in their spectra. Realistic calculations for these nuclei are shown in detail for comparison. The implications of a core with non-zero spin are investigated and illustrated for 17Ne ( 15O + p + p). Dimensionless units allow predictions for systems of different scales. [ABSTRACT FROM AUTHOR]

A series of on-line mass separation experiments have been performed at the IRIS facility to measure the yield and release of Rb and Cs neutron-rich isotopes produced by fission reaction of238U. A 1 GeV proton beam was used to bombard uranium carbide targets with the densities of 11 g/cm3 and 1.5 g/cm3 held at temperatures in the range (2000-2230)°C. The release curves of Rb and Cs long-lived isotopes were measured from both kinds of targets. The overall production efficiency was determined making use of experimentally measured cross-sections of that isotope production. Comparison of the experimental yields of Rb and Cs isotopes with the calculated ones after corrections for losses due to finite release times suggests that the diffusion is the dominating process reducing the efficiency for short-lived isotopes. When normalized to the same thickness, an enhancement for the high-density rod target of the measured isotope yields is observed when going far from stability. This is possibly explained by the reactions induced by secondary neutrons. A significant odd-even effect with higher yields of Cs even neutron isotopes has been observed, confirming a similar effect obtained in earlier experiments. [ABSTRACT FROM AUTHOR]

The laser ion source has been used for the study of the isotope shifts of neutron-deficient Eu isotopes. The extension of the region of applicability of the method by using the- and-radiation detection is reported. We have measured the isotope shifts of the europium optical line 576.520 nm for. To increase the laser ion source efficiency an axial magnetic field (350 gauss) was applied. Nearly a twofold rise of the ionization efficiency for Eu was observed. By using the effect of optical ion bunching an increase of the selectivity was obtained. The isotope shift data forare in agreement with the previously measured isotope shifts for these nuclides. The new data forand refined data forpoint to a gradual increase of the deformation for these isotopes. Comparisons with microscopic-macroscopic calculations and calculations in the framework of the Hartree-Fock model were performed. [ABSTRACT FROM AUTHOR]

In the frame of the R&D program for the SPES project of the Legnaro Laboratories, the production yields of Rb, In and Cs isotopes have bean measured at the synchrocyclotron of the Petersburg Nuclear Physics Institute (PNPI) of Gatchina (Russia). Production yields for direct proton fission and neutron-induced fission on a high-density UC2 powder target are compared. The overall efficiencies as a function of the target temperature have been measured. [ABSTRACT FROM AUTHOR]

Production yields and β-decay half-lives ( T1/2) of very neutron-rich indium isotopes were determined at CERN/ISOLDE using isobaric selectivity of a resonance-ionization laser ion-source. Beta-delayed neutron (βdn) multiscaling measurements have yielded improved T1/2 for 206(6) ms 132In, 165(3) ms 133In and 141(5) ms 134In. With 92(10) ms 135In, a new r-process nuclide has been identified which acts as an important “waiting point” in the In isotopic chain for neutron densities in the range nn≃ 1024-1026 n/cm3, where the r-matter flow has already passed the A≃ 130 abundance peak region. [ABSTRACT FROM AUTHOR]

The interconnection between the resonances and virtual states of a three-body system and the resonances and virtual states in its two-body subsystems is investigated using the Borromean halo nucleus 11Li as a realistic example. The three-body core + neutron + neutron model is used, where the neutron-core interaction is fixed to reproduce a given s-wave virtual state and a p-wave resonance. The neutron-neutron interaction is then multiplied by a factor which is progressively changed from 0 to 1 and the resulting trajectories of the three-body states in the complex energy plane are investigated. [ABSTRACT FROM AUTHOR]