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L. Nalpas

Bio: L. Nalpas is an academic researcher from DSM. The author has contributed to research in topics: Nucleon & Neutron. The author has an hindex of 32, co-authored 124 publications receiving 2646 citations.


Papers
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Journal ArticleDOI
14 Oct 2004-Nature
TL;DR: Here, the reactions of the halo nucleus 6He with a 238U target are studied, which are used as an experimental signature to identify the contribution of the fusion and transfer channels to the total cross-section.
Abstract: 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.

140 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the transverse energy of light particles as an impact parameter selector and compared the results with dynamical models with which a good agreement was obtained. But the results were not compared to dynamical model with which good agreement is obtained.
Abstract: Experimental data obtained with the 4{pi} multidetector system INDRA are used to study the light charged particle (LCP, Z{le}2) and intermediate mass fragment (IMF, Z{ge}3) production in peripheral and semicentral collisions of Xe and Sn at 50 MeV/nucleon. It is found that a sizable fraction of the detected LCP`s and IMF`s originates from the midvelocity region. These fragments can be seen to come either from a prompt (preequilibrium) mechanism or from a slower but dynamically influenced emission process. The relative magnitude of the dynamically influenced emission relative to the isotropic statistical evaporation is presented as a function of the transverse energy of light particles, used as an impact parameter selector. The results are compared to dynamical models with which a good agreement is obtained. {copyright} {ital 1997} {ital The American Physical Society}

90 citations

Journal ArticleDOI
TL;DR: In this paper, the INDRA multidetector was used to study multifragmentation processes in central collisions for the Xe + Sn reaction at 50 A MeV, and the fragment kinetic energy spectra indicated a fast disintegration of the system with a radial collective motion of about 2 A MEV.

86 citations

Journal ArticleDOI
TL;DR: The 4π array INDRA was used to detect nearly all charged products emitted in Ar + Ni collisions between 52 and 95 MeV/u as mentioned in this paper, and the charge, mass and excitation energy E ∗ of the quasi-projectiles have been reconstructed event by event.

84 citations

Journal ArticleDOI
TL;DR: The N = 28 shell closure has been investigated via the 46Ar(d,p)47Ar transfer reaction in inverse kinematics and a reduction of the N =28 gap is deduced by 330(90) keV and spin-orbit weakenings of approximately 10(2) and 45(10)% for the f and p states, respectively.
Abstract: The N � 28 shell closure has been investigated via the 46 Ard; p� 47 Ar transfer reaction in inverse kinematics. Energies and spectroscopic factors of the neutron p3=2, p1=2, and f5=2 states in 47 Ar were determined and compared to those of the 49 Ca isotone. We deduced a reduction of the N � 28 gap by 330(90) keV and spin-orbit weakenings of ' 10� 2� and 45(10)% for the f and p states, respectively. Such large variations for the f and p spin-orbit splittings could be accounted for by the proton-neutron tensor force and by the density dependence of the spin-orbit interaction, respectively. This contrasts with the picture of the spin-orbit interaction as a surface term only.

81 citations


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Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the major progress achieved during the last decade in isospin physics with heavy ion reactions and discuss future challenges to the most important issues in this field.

940 citations

Journal Article
TL;DR: In particular, the role of mesons, isobars and quarks in nuclear structure and the use of complex nuclei for probing fundamental symmetries is discussed in this paper.

665 citations

Journal ArticleDOI
TL;DR: A review of the evidence on the properties of the nuclei A = 8, 9 and 10, with emphasis on material leading to information about the structure of the A =8, 9, 10 systems is given in this paper.

643 citations