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International audience; A complete study of the 6,7Li + p reactions was performed by measuring the complete net of reaction channels at the energy range of ∼ 2 to 5 MeV/nucleon. The experiments were performed at the MAGNEX facility of the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) in Catania. The breakup channel was identified by means of a new algorithm, MULTIP, which gives the possibility of following up the decay of the nucleus into two or more constituent particles from the rest frame of the nucleus itself to the laboratory frame. Angular distributions were obtained for all reaction products and were considered within the Continuum Discretized Coupled Channels (CDCC) framework. The results of the CDCC calculations were found in a very good agreement with the experimental data presenting a strong evidence for the important influence of coupling to breakup on the elastic channel.

Elastic scattering and breakup angular distribution measurements for the systems 6,7Li + p were performed at the MAGNEX facility of the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) in Catania, in the energy range of (2.3-5.4)AMeV. The breakup channel was identified and quantified adopting the algorithm MULTIP.Within this algorithm which is a Monte Carlo simulation code, the history of the breakup fragments can be tagged from the rest frame of the decay nucleus itself to the laboratory frame. Angular distribution data of both elastic scattering and breakup were analyzed under the same theoretical model and the influence of continuum on the elastic channel was investigated., The research leading to these results was partially funded by the European Union Seventh Framework Programme FP7/2007-2013 (Grant Agreement No. 262010ENSAR) and also by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 714625).

Total reaction cross sections at near barrier energies (9-13 MeV) were measured for the system 6Li+28Si adopting a new technique. The results will be discussed in terms of the threshold anomaly at barrier

Exclusive breakup measurements have been performed for the Li6+p system in inverse kinematics at Li6 incident energies of 25 and 29 MeV. The results are considered in the Continuum Discretized Coupled-Channels framework, together with elastic scattering data at 16, 20, 25, and 29 MeV, obtained simultaneously in the same experiment and reported previously. Good agreement between data and theory is observed, interpreted as evidence for strong coupling to the continuum. The direct and sequential (via the Li631+ resonance) breakup cross sections are found to be equally large at the higher incident energies but the dominant effect on the elastic scattering is due to coupling to the sequential breakup. This effect remains dominant even at the lowest energy of 16 MeV, despite the negligible cross section for excitation of the resonance at this low incident energy.

The present work provides a literature survey of elastic scattering of exotic nuclei from 6He to 17F. It presents a set of definitions that allow different analyses to be put into a common language. A calculational approach is proposed that yields consistent results across different beams and targets so that conclusions concerning the influence of virtual and real breakup as well as transfer couplings on the elastic scattering may be drawn. Calculations of elastic scattering around the Coulomb barrier are emphasised, employing a Pb target whose large Z allows the interplay between nuclear and Coulomb forces to be exploited to maximise possible effects arising from proton or neutron haloes or skins. A series of test calculations is performed and where possible compared to data, demonstrating that there are instances where coupling to transfer channels can have a large effect on the elastic scattering angular distributions. By careful choice of target/beam combination, different aspects of the coupling effects may be emphasised.

The structure of the light exotic nucleus 8 He was investigated using direct reactions of the 8 He SPIRAL beam on a proton-rich target. The (p,p') scattering to the 2 1 + state, the (p,d) 7 He and (p,t) 6 He transfer reactions, were measured at the energy E l a b = 15.7 A.MeV . The light charged particles (p,d,t) were detected in the MUST Si-strip telescope array. The excitation spectrum of 8 He was extracted from the (p,p') reaction. Above the known 2 1 + excited state at 3.6 MeV, a second resonance was found around 5.4 MeV. The cross sections were analyzed within the coupled-reaction channels framework, using microscopic potentials. It is inferred that the 8 He ground state has a more complex neutron-skin structure than suggested by previous α + 4 n models assuming a pure ( 1 p 3 / 2 ) 4 configuration.

Elastic-scattering measurements have been performed for the $^{6}\mathrm{Li}+p$ system in inverse kinematics at the energies of 16, 20, 25, and 29 MeV. The heavy ejectile was detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud in Catania, Italy. The results are considered in a Jeukenne-Lejeune-Mahaux and a continuum discretized coupled-channel calculation framework.

Elastic scattering measurements have been performed for the 6Li+p system in inverse kinematics at the energies of 16, 20, 25 and 29 MeV. The heavy ejectile was detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS) in Catania, in the angular range between ∼20 and 120 in the laboratory system, giving us the possibility to span almost a full angular range in the center of mass system. Results will be presented and discussed for one of the energies. European Union 262010-ENSAR

We have undertaken the study of 6 Li breakup on a 28 Si target near the Coulomb barrier through an angular distribution measurement. Alpha particles were recorded in coincidence with deuterons in order to determine exclusively the breakup of lithium. The results are analysed and are discussed, in a continuum discretized coupled channel framework (CDCC).

The production of α-particles in the reactions 6,7 Li+ 28 Si was studied as a means to disentangle the various reaction channels at near-barrier energies. The competition between compound and direct reactions was determined by using the shape of angular distributions and statistical model calculations. DWBA calculations were also performed to probe the various direct channels. It was found that, approaching barrier, transfer channels are the most dominant for both reactions. For 7 Li+ 28 Si d-transfer is one of the contributing channels without excluding t-transfer, while for 6 Li+ 28 Si, n-transfer and p-transfer have substantial contribution but without excluding d-transfer.

Elastic scattering angular distributions for systems with reduced mass between 3 and 34 and energies varying between 25 and 120 MeV/nucleon were analyzed. The stable $^4$He, its exotic partner $^6$He, and the weakly bound $^{6,7}$Li nuclei were included as projectiles in the systematics. Optical model data analyzes were performed with an adjustable factor of normalization included in the imaginary part of the potential. These analyzes indicated a reduction of absorption for systems with small reduced masses that was detected due to the refractive nature of the scattering by light systems., Comment: 16 pages, 7 figures

Quantum tunnelling through a potential barrier ( such as occurs in nuclear fusion) is very sensitive to the detailed structure of the system and its intrinsic degrees of freedom(1,2). A strong increase of the fusion probability has been observed for heavy deformed nuclei(3). In light exotic nuclei such as He-6, Li-11 and Be-11 ( termed 'halo' nuclei(4)), the neutron matter extends much further than the usual nuclear interaction scale. However, understanding the effect of the neutron halo on fusion has been controversial - it could induce a large enhancement of fusion(5), but alternatively the weak binding energy of the nuclei could inhibit the process(6). Other reaction channels known as direct processes ( usually negligible for ordinary nuclei) are also important: for example, a fragment of the halo nucleus could transfer to the target nucleus through a diminished potential barrier. Here we study the reactions of the halo nucleus He-6 with a U-238 target, at energies near the fusion barrier. Most of these reactions lead to fission of the system, which we use as an experimental signature to identify the contribution of the fusion and transfer channels to the total cross-section. At energies below the fusion barrier, we find no evidence for a substantial enhancement of fusion. Rather, the ( large) fission yield is due to a two-neutron transfer reaction, with other direct processes possibly also involved.

The structure of radioactive beams is investigated using the simplest possible probe: the proton used as a target in inverse kinematic reactions. From (p, p′) reactions, information on the neutron and proton transition densities is obtained through the comparison between the measured inelastic cross sections and the ones calculated using a microscopic potential and theoretical densities. (p, p′) inelastic scattering data to the first excited state for the halo nucleus 6He and for other nuclei 34Ar and 34,36S have been measured at GANIL using the MUST telescopes. This allows one to extract the global features of the transition densities, as shown for the halo nucleus 6He. We can also probe the evolution of the shell structure along isotopic chains in moving towards the neutron or proton drip lines. The example of the sulfur isotopic chain is discussed.

The 6 Li + 28 Si elastic scattering was studied at near-barrier energies with the aim to probe the threshold anomaly. Angular distributions were measured over a wide angular range (θlab = 25 ◦ to 150 ◦ ) at 4 energies, namely, 7.5, 9, 11 and 13 MeV. The present data together with previous ones at higher energies, as well as elastic scattering data of 6 Li on various targets at near barrier energies, were analyzed by using optical potentials obtained in a double-folding framework. It was found that the strength of the real part of the potential remains almost independent of energy down to, and possible even below, barrier, while the strength of the imaginary part presents an increase at near barrier energies. The results are discussed.  2003 Elsevier Science B.V. All rights reserved.

Following mass measurements in the region N = 20 and N = 28, we have studied inelastic nuclear scattering for the nuclei 34Si, 33Al and 32Mg. No evidence for a low-lying shape isomeric 0+ state was found in 34Si, and an upper limit for the population cross-section could be established, rendering its existence very unlikely. A new transition was found in 33Al, that is a good candidate for a 2p–2h state and therefore a determination of the 2p–2h gap at N = 20. Inelastic nuclear scattering strongly excites 3− states, as seen in 34Si. A strong transition was found in 32Mg that should correspond to the first 3− in this nucleus, lying very low as compared to theory and systematics in this region.

The structure of 6 He is explored with proton elastic and inelastic scattering to the first 2 + excited state (Q =− 1. 8M eV) of 6 He in the inverse kinematics using a 24.5 A MeV 6 He beam. The distorted wave approximation (DWA) with an optical potential obtained by folding an effective nucleon–nucleon (NN) g-matrix with the 6 He density matrix elements as given by a large basis shell model is used to analyse the data. The comparison of predictions with the data confirms the view that 6 He has

Elastic proton scattering is investigated as a means for probing density the distribution of exotic neutron-rich nuclei. In this context, the calculations for elastic p+8He scattering within the JLM and eikonal-approximation models are performed by using the cluster-orbital-shell-model-approximation parameters for the density distribution. The results of the calculations are compared with existing experi-mental data. It is found that, at large scattering angles, both models are sensitive to the extension of valence neutrons.

Angular distributions of elastically scattered 8 He ions on 4 He and on protons at the beam energy of 26 MeV/ n are presented. An attempt to observe a backward-angle rise of the 8 He + 4 He cross-section is reported. The forward-angle 4 He data are analyzed with a double folding, density dependent model. Finite range DWBA was applied in order to estimate the contributions from the transfer reactions. It was found that the 2-step process is more important than the 1-step transfer. It seems that eikonal approximation is applicable for the description of elastic scattering 8 He + p at this energy.

Following mass-measurements in the region N = 20 and N = 28, we have studied inelastic nuclear scattering for the nuclei 3 4 Si, 3 3 Al and 3 2 Mg. No evidence for a low lying shape isomeric 0 + state was found in 3 4 Si,and an upper limit for the population cross section could be established, rendering it's existence very unlikely. A new transition was found in 3 3 Al, that is a good candidate for a 2p-2h state and therefore a determination of the 2p-2h gap at N = 20. Inelastic nuclear scattering strongly excites 3 - states, as seen in 3 4 Si. A strong transition was found in 3 2 Mg that should correspond to the first 3 - in this nucleus, lying very low as compared to theory and systematics in this region.

A new Secondary Electron gas Detector (SED) is under development to be used in conjunction with an emissive foil to detect low energy heavy ions as an alternative to micro-channel plates. It could measure position and time of flight. Secondary electrons are accelerated to 10 keV so that they can cross through the 0.9 μm Mylar entrance window. The electrons then are multiplied in the isobutane gas of the detector at 4– 10 Torr . A time resolution of 150 ps and a spatial resolution of 3 mm have been obtained by using californium fission fragments on a prototype detector of 7×7 cm 2 . The advantage of the SED against MCP is that its size is not limited. Our final goal is to build a large size detector (15×40 cm 2 ) that will operate at the focal plane of the VAMOS magnetic spectrometer at GANIL.

Proton elastic scattering and inelastic scattering to the first excited state of 6He have been measured over a wide angular range using a 40.9A MeV 6He beam. The data have been analyzed with a fully microscopic model of proton-nucleus scattering using 6He wave functions generated from large space shell model calculations. The inelastic scattering data show a remarkable sensitivity to the halo structure of 6He., Comment: 9 pages, 3 figures. RevTeX. Replaced figure 3 with updated figure

The reaction cross section for the halo nucleus 6 He on hydrogen has been measured at 36 MeV/nucleon using the transmission method and a value of σ R =409±22 mb was obtained. A coherent analysis within a microscopic model of this result in conjunction with (p,p) and (p,n) angular distributions has allowed the interaction potential to be uniquely determined. This analysis also allowed the 6 He density distribution to be explored.

Although there is no proof of the validity of the method, in a lot of papers, one computes the Second derivative of the the experimental fusion cross section multiplied by the energy to extract the fusion barriers directly from the experiment. The purpose of this paper is to check the consistency of the method, as experimental points are sandwiched inside their error bars. We therefore analysed the validity, by giving ourselves a cross section σ(E), resulting from the coupled channel calculation code ECIS, upon which, in spite of the complexity of the calculations, we have full control. We took these calculated points as the “experimental” ones and we altered them by multiplication by small random numbers. This is intended to simulate the error bars, of which we want to examine the influence on the fusion barriers. We find that in spite of the rough predictions yielded by the second derivative method, this task requires data with a precision difficult to reach. Furthermore, a careful check of the predictions of this method for coupled channels calculations shows that, due to the errors bars, this approach adds spurious results.

The determination of ratio of neutron over proton matrix elements by inelastic proton scattering, for 0(+)-->2(+) transitions, is investigated via the comparison between experimental data and theoretical calculations. Calculations into the context of a macroscopic and a microscopic description are performed for a wide mass range nuclei: O-18, Si-30, S-32,S-34, Ca-48, Sr-88, for which these ratios were determined previously with an independent technique. At that point the choice of the theoretical model may be very critical, It is thus the purpose of this investigation to point out the most suitable model. It is found that in general both theoretical models can be employed for the reliable determination of neutron over proton matrix element ratios. (C) 1999 Elsevier Science B.V. All rights reserved. Nuclear Physics A

We present the results of an experimental comparative study of the ${}^{40,48}\mathrm{Ca}$ resonance spectra between 6 and 12 MeV. The power of the heavy ion reaction ${}^{40,48}\mathrm{Ca}{(}^{86}\mathrm{Kr},{ }^{86}{\mathrm{Kr}}^{\ensuremath{'}}{)}^{40,48}{\mathrm{Ca}}^{*}$ at 60 MeV per nucleon was exploited to enhance greatly the low energy part of inclusive spectra in order to look for the possible presence of a low energy dipole mode in ${}^{48}\mathrm{Ca}$ due to a neutron skin. We did not observe any difference in the $l=1$ channel and therefore found no evidence of this mode. In the $l=2$ channel, an important excess of strength was observed in ${}^{40}\mathrm{Ca}$ compared to ${}^{48}\mathrm{Ca}$.

High energy γ -rays ( E γ >35 MeV) have been measured in coincidence with heavy residues emitted in reactions induced by a 37 MeV/u 36 Ar beam on a 98 Mo target. The γ -ray yield increases strongly with increasing linear momentum transfer indicating the importance of two-body collisions in the transfer mechanism. The high energy γ -ray multiplicity has been used to correlate the linear momentum transfer to the impact parameter. This correlation is compared to dynamical BNV simulations to show the essential role of two body nucleon-nucleon collisions at these bombarding energies.

A new method to determine compound nuclear lifetimes at high excitation energies is proposed and applied to the system 12 C( 28 Si, α ) 36 Ar at two different bombarding energies, 190 and 277 MeV. The alpha particle spectra show a structure which directly reflects the fluctuating behavior of the first de-excitation step. Coherence widths and thus lifetimes for the nucleus 36 Ar were obtained via a correlation function analysis. The results at low excitation energies are consistent with standard statistical models while the result at high excitation energy is compatible with a theoretically predicted change of the level density parameter.

Inelastic scattering of {sup 40}Ca on {sup 40}Ca at 50 MeV/nucleon has been measured in coincidence with light charged particles detected over a large angular domain. The giant resonance region of the inelastic spectrum is shown to be dominated by the isoscalar giant quadrupole resonance. The characteristics of the emitted protons allow us to separate four reaction mechanisms contributing to the high excitation energy region of the inelastic spectrum (E{sup {asterisk}}{gt} 30 MeV): pickup breakup, knockout, inelastic scattering to high-lying target states, and a new mechanism responsible for the emission of fast-moving protons. A sizable direct decay branch towards hole states of {sup 39}K is measured for the giant quadrupole resonance in {sup 40}Ca. Evidence is given for the excitation of the two-phonon giant quadrupole resonance, characterized by its direct decay scheme. The energy and width of this two-phonon state are in agreement with a harmonic picture for collective nuclear excitations. {copyright} {ital 1997} {ital The American Physical Society}

The energy spectra of the γ-rays emitted in the 35Cl + 92Mo reaction at incident energy E = 260 MeV were measured in coincidence with the ejectiles produced in dissipative reaction events. The cumulative energy spectrum of the γ-rays coming from the decay of the ejectiles was calculated within the statistical model and its comparison to the experimental spectrum evidences an excess in the data for Eγ = 8 to 12 MeV. Such an excess, fitted with a Lorentz curve, is attributed to the preequilibrium GDR γ-decay of the intermediate dinuclear system. The centroid energy of the Lorentz curve corresponds to a dipole oscillation along the symmetry axis of the system and its width is found to be comparable to that of the ground state GDR low energy component of the deformed dinucleus. The small quantal dispersion Δl = (10.3 ± 0.1)ħ of the entrance channel angular momentum, determined by analysing the dissipative fragment angular distribution in the framework of the Strutinsky model, is suggested to limit the broadening of the preequilibrium GDR width.

International audience; We have measured the $^{6}$He(p, t)$\alpha$ transfer reaction in inverse kinematics at 25MeV/nucleon. The data were compared to DWBA calculations in order to extract the spectroscopic amplitudes for $\alpha$+2n and t + t configurations in the ground state of $^{6}$He.

Fusion cross sections were measured for ${}^{8}$B + ${}^{28}$Si at near-barrier energies by detecting the alpha particles produced in the evaporation process. The results present a small suppression with respect to one-barrier penetration model predictions, which could be attributed to incomplete fusion processes and do not differ appreciably from fusion cross sections obtained with weakly bound but stable projectiles on the same target. Comprehensive comparisons of fusion cross sections at sub- and near-barrier energies with various light weakly bound projectiles support a simple tunneling probability with slight modifications due to coupled-channel effects.

The elastic scattering p( 6 He, 6 He)p and charge exchange reaction p( 6 He, 6 Li)n have been measured in reverse kinematics with a secondary 6 He beam. The angular distributions for these reactions were obtained. In the case of the charge exchange reaction, the ratio of the cross section for the Gamow-Teller transition to the ground state, and for the Fermi transition to the isobaric analog state is a measure of the relative strength of the two components of the exchange interaction, V στ and V τ . This ratio is found to be compatible with existing systematics for stable T = 1 nuclei, and no clear signature of a halo structure was found in the present data.

Gamma-rays emitted from hot nuclei of mass around 115 and excitation energies above 300 MeV, formed in the 36 Ar + 90 Zr at 27 MeV/u, 36 Ar + 94 Zr at 32 MeV/u and 36 Ar + 98 Mo at 37 MeV/u, have been measured with the MEDEA multidetector in coincidence with evaporation residues. The γ-ray yield from the decay of the Giant Dipole Resonance is independent of excitation energy and of bombarding energy.

The cross sections for K + meson production in collisions of 36 Ar on 12 C, nat Ti and 181 Ta at an incident energy of 92 MeV per nucleon have been measured. A description of the set-up and of the method is given ; it is based on measurement of the muon decay of the positive kaon. At such a low incident energy the K + production seems to be more sensitive to the available energy in the center of mass of the nucleus-nucleus system than to the coulomb corrected incident energy normalized to the production threshold in a free nucleon-nucleon process.

A. Pakou1, N. Patronis1, D. Pierroutsakou2, A.M. Sanchez-Benitez3, L. Acosta3,4, N. Alamanos5, A. Boiano2, G. Inglima6, D. Filipescu7, T. Glodariu7, A. Guglielmetti8, M. La Commara6, G. Lalazissis9, I. Martel3, C. Mazzocchi8, M. Mazzocco10, P. Molini10, C. Parascandolo2, M. Sandoli6, C. Signorini10, R. Silvestri6, F. Soramel10, M. Romoli2, E. Stiliaris11, A. Trzcinska12, K. Zerva1, E. Vardaci6, A. Vitturi10.

Expérience GANIL/SPIRAL/MUST2/E525S; The low-lying spectroscopy of 6He was investigated via the 2-neutron transfer reaction p(8He, t) with the 8He beam delivered by the SPIRAL facility at 15.4 A MeV. The light charged particles produced by the direct reactions were measured using the MUST2 Si-strip telescope array. Above the known 2+ state, two new resonances were observed: at E∗ = 2.6±0.3 MeV (width Γ = 1.6±0.4 MeV) and at 5.3±0.3 MeV with Γ = 2 ± 1 MeV. Through the analysis of the angular distributions, they correspond to a 2+ state and to an L = 1 state, respectively. These new states, challenging the nuclear theories, could be used as benchmarks for checking the microscopic inputs of the newly improved structure models, and should trigger development of models including the treatments of both core excitation and continuum coupling effects.

Inelastic scattering of 84 MeV/u 17 O projectiles has been used to excite the giant resonances (GR) in 232 Th. The deduced parameters (width, energy, EWSR) of the isoscalar giant quadrupole resonance are in agreement with the known systematics. The observed giant monopole resonance strength, 100% of the EWSR, is consistent with other recent experimental results using heavy-ion projectiles. Strength is also observed at high excitation energy. The fission probability of GR in 232 Th has been measured by detecting the fission fragments in coincidence with the inelastically scattered particles. A structure is observed in the fission coincidence spectrum around 10 MeV, which can be attributed to the fission decay of giant resonances. The measured fission probability is consistent with statistical decay of the GQR.

Inelastic scattering of 50 MeV/nucleon [sup 40]Ca on [sup 40]Ca was measured in coincidence with protons in order to investigate the excitation and decay of highly excited states in [sup 40]Ca. The proton decay pattern corresponding to an excitation region around 34 MeV shows the characteristic behavior expected of the direct decay of a two-phonon state. Thus, by using this novel method, the presence of a double-phonon state built with isoscalar giant resonances in [sup 40]Ca is demonstrated.

The response function of MEDEA BaF2 crystals to high energy photons, up to 280 MeV, has been studied using monochromatic γ-rays from the in flight annihilation of positron beams. The experimental response functions are compared to the results of Monte Carlo simulations based on the EGS3 code and parametrized over the whole investigated energy range.

The excitation functions for $^{7}\mathrm{Li}+^{28}\mathrm{Si}$ quasielastic scattering at ${150}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${170}^{\ifmmode^\circ\else\textdegree\fi{}}$ have been measured at sub- and near-barrier energies (0.6 to 1.3 ${\mathrm{V}}_{\mathrm{B}}$) and the corresponding barrier distributions derived. The results were analyzed within the framework of the optical model using a procedure similar to one used on previous results for $^{6}\mathrm{Li}+^{28}\mathrm{Si}$ employing double-folded potentials calculated using the BDM3Y1 effective interaction. The variation of the surface strength of the optical potential as a function of incident energy was compared for the two systems $^{6}\mathrm{Li}+^{28}\mathrm{Si}$ and $^{7}\mathrm{Li}+^{28}\mathrm{Si}$, the barrier distributions being used to help better define the potential at the lowest energies. The barrier distributions were also analyzed with continuum-discretized coupled-channel (CDCC) and coupled reaction channel (CRC) calculations as a means of investigating the influence of breakup and transfer reactions on these quantities for these light, weakly bound projectiles.

A recent measurement of the $^{11}\mathrm{Be}+^{64}\mathrm{Zn}$ quasielastic scattering angular distribution exhibits a non-Fresnel-type pattern, in contrast to $^{6}\mathrm{He}+^{64}\mathrm{Zn}$ elastic scattering but similar to that for the elastic scattering of $^{6}\mathrm{He}$ from heavy targets. We show by means of continuum discretized coupled-channels (CDCC) calculations that this unusual behavior of $^{11}\mathrm{Be}$ is caused by the much greater importance of nuclear coupling to the continuum in $^{11}\mathrm{Be}$ compared to $^{6}\mathrm{He}$, where Coulomb dipole coupling is mainly responsible for the non-Fresnel-like shape, when present. We also show that the dynamic polarization potentials derived from the CDCC calculations seem to follow a universal form as a function of radius.

A new detector system dedicated for very/super heavy elements (VHE/SHE) detection that decay by spontaneous fission is presented. Such a decay mode of nuclei can be found e.g. in the region of Z ≈100 (Fermium). Future experiments realized in the frame of French-Polish collaboration at the cyclotrons in GANIL and in the Heavy Ion Laboratory (HIL), University of Warsaw, is described. The results of test measurements made in the HIL for reactions 20 Ne (8 A . MeV )+120 Sn , 179 Au are presented.

The Web and its tools of orientation: how better to understand the information available on the Internet by the analysis of references? In the incessant and chaotic frenzy of the Internet, suitable tools and techniques are urgently required for use by information professionals. The Internet has become a leading venue for communication among researchers, both scientists and other scholars. The role of mediation for these professionals has never been so important, owing to the actual deficiencies of the search systems on the Internet. This article expounds the tools that are now available for the identification and evaluation of Internet sources. After a discussion of the techniques of discrimination and cartography, a method of constructing a navigation map of the Web by the analysis of citations is explained.

The production of neutral pions has been studied in the 16 O+ 27 Al, 58 Ni, 208 Pb reactions at 95 MeV/nucleon. Inclusive pion differential distributions d σ d p t , d σ d T π , and d σ d Ω have been measured by detecting the two-pion decay γ-rays in a setup of 8 lead glass Cherenkov detector telescopes. The data are discussed in the framework of a moving thermal source model. It is shown that the shape of the pion energy spectra is better described if mean field effects on the primary pion-production cross section and pion reabsorption are included in the calculation.

Elastic backscattering measurements were performed for the weakly bound nucleus $^{6}\mathrm{Li}$ on a $^{28}\mathrm{Si}$ target at sub- and near-barrier energies (0.6 to 1.3 V${}_{C.B.}$). Excitation functions of elastic scattering cross sections were measured at ${150}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${170}^{\ifmmode^\circ\else\textdegree\fi{}}$ and the corresponding ratios to Rutherford scattering and relevant barrier distributions were formed. The results are discussed in terms of the potential threshold anomaly and the reaction mechanisms involved.

Fusion cross sections are extracted for the (7)Li + (28)Si system, via reaction cross section and transfer measurements at sub- and near-barrier energies (E(lab) = 5.7 to 14 MeV). The energy evolution of transfer to reaction cross section ratios is determined with the aid of CDCC calculations, which subsequently allows the deduction of fusion cross sections at sub- and near-barrier energies. It is shown that fusion can be well represented in a BPM context. Fusion cross sections are compared for the systems (7)Li + (28)Si and (6)Li + (28)Si, the latter studied previously, and are found to exhibit different strengths. Last, the direct channels determined at 13 MeV, are found to be dominated by a 2n-transfer mechanism. European Physical Journal A