Role of high<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow></mml:math>values in the onset of incomplete fusion

38 pages, 15 figuresPeripheral collisions with radioactive heavy-ion beams at relativistic energies are discussed as an innovative approach for probing the transient regime experienced by fissile systems evolving towards quasi-equilibrium. A dedicated experiment using the advanced technical installations of GSI, Darmstadt, permitted to realize ideal conditions for the investigation of relaxation effects in the meta-stable well. Combined with a highly sensitive experimental signature, it provides a measure of the transient effects with respect to the flux over the fission barrier. Within a two-step reaction process, 45 proton-rich unstable spherical isotopes produced by projectile-fragmentation of a stable 238U beam have been used as secondary projectiles. The fragmentation of the radioactive projectiles on lead results in nearly spherical compound nuclei which span a wide range in excitation energy and fissility. The decay of these excited systems by fission is studied with a dedicated set-up which permits the detection of both fission products in coincidence and the determination of their atomic numbers with high resolution. The width of the fission-fragment nuclear charge distribution is shown to be specifically sensitive to pre-saddle transient effects and is used to establish a clock for the passage of the saddle point. The comparison of the experimental results with model calculations points to a fission delay of (3.3+/-0.7).10-21s for initially spherical compound nuclei, independent of excitation energy and fissility. This value suggests a nuclear dissipation strength at small deformation of (4.5+/-0.5).1021s-1. The very specific combination of the physics and technical equipment exploited in this work sheds light on previous controversial conclusions

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“…The inadequate description of several additional aspects of fission process was discussed recently in Refs. [52,145].…”

Section: ) Physics Interplay and Model Dependencementioning

confidence: 99%

Fragmentation of spherical radioactive heavy nuclei as a novel probe of transient effects in fission

Schmitt

Schmidt²,

Kelić³

et al. 2010

Phys. Rev. C

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“…Ferrites have gained worldwide attention due to their extremely wide range of applications in the field of telecommunications, electronics and bioceramics [4][5][6][7][8][9]. Both ceramics and ferrites are suitable candidates for microwave applications [10,11].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Co-Zr doped nanocrystalline strontium hexaferrites by sol-gel auto-combustion route using sucrose as fuel and study of their structural, magnetic and electrical properties

Kaur

Chawla

Meena

et al. 2016

Ceramics International

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“…A number of theoretical approaches for understanding the incomplete fusion process have been developed, as recently reviewed in [16,17,18]. These span a range of concepts and considerations, including breakup-fusion, angular momentum window for incomplete fusion, promptly emitted particles, Fermijet, exciton, and moving source, thereby explaining the measured energy spectra and angular distribution of the emitted fragments and population of angular momentum in the compound system.…”

mentioning

confidence: 99%

Role of the cluster structure of 7Li in the dynamics of fragment capture

et al. 2013

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Exclusive measurements of prompt γ-rays from the heavy-residues with various light charged particles in the 7 Li + 198 Pt system, at an energy near the Coulomb barrier (E/V b ∼ 1.6) are reported. Recent dynamic classical trajectory calculations, constrained by the measured fusion, α and t capture cross-sections have been used to explain the excitation energy dependence of the residue cross-sections. These calculations distinctly illustrate a two step process, breakup followed by fusion in case of the capture of t and α clusters; whereas for 6 He + p and 5 He + d configurations, massive transfer is inferred to be the dominant mechanism. The present work clearly demonstrates the role played by the cluster structures of 7 Li in understanding the reaction dynamics at energies around the Coulomb barrier.Keywords: Particle gamma coincidence, Weakly bound nuclei, Breakup fusion, Nuclear cluster structure, Classical dynamical model In weakly bound nuclear systems, correlation among nucleons and pairing are manifested, among others, as an emergence of strong clustering and exotic shapes. This has renewed interest in the understanding of clusters based on concepts of molecular physics and the role of cluster states in nuclear synthesis [1,2]. Lithium isotopes present a unique example of nuclear clustering, with lighter isotopes ( 6,7 Li) having a well known α + x cluster structure and the heaviest bound isotope ( 11 Li) exhibiting a two neutron Borromean structure.9 Li has also been described as 6 He + t in a recent work [3]. 7 Li is an equally interesting case with its well known weakly bound α + t structure (S α/t = 2.47 MeV), as well as less studied more strongly bound clusters 6 He + p (S6 He/p = 9.98 MeV) and 5 He + d (S5 He/d = 9.52 MeV) [4,5].Recent studies with weakly bound nuclei have also focused on the understanding of the role of novel structures in the reaction dynamics [6]. Dominant reaction modes in nuclei with low binding energies, involve inelastic excitation to low lying states in the continuum or transfer/capture of one of the cluster fragments from their bound/unbound states to the colliding partner nucleus [6,7,8]. The role of inelastic excitation of low lying unbound states and transfer in the fusion hindrance, observed at energies well below the barrier, is also a topic of current interest [9,10]. When the capture occurs from unbound states of the projectile, the process could be looked upon as a two step process, breakup followed by fusion (breakup fusion) [11,12,13]. In case of well bound nuclei, nuclear reaction related to cap- * Corresponding author Email address: aradhana@barc.gov.in (A. Shrivastava ) ture of heavy fragments by the target has been identified as incomplete fusion or massive transfer [14] and occurs predominately at energies ≥ 10 MeV/A. For weakly bound cluster nuclei such as 6,7 Li, the former has been shown to be important both above and at energies much below the Coulomb barrier [10,15]. Earlier studies have found the process of breakup fusion to be more dominant ove...

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Role of highℓvalues in the onset of incomplete fusion

Cited by 35 publications

References 76 publications

Fragmentation of spherical radioactive heavy nuclei as a novel probe of transient effects in fission

Fragmentation of spherical radioactive heavy nuclei as a novel probe of transient effects in fission

Synthesis of Co-Zr doped nanocrystalline strontium hexaferrites by sol-gel auto-combustion route using sucrose as fuel and study of their structural, magnetic and electrical properties

Role of the cluster structure of 7Li in the dynamics of fragment capture

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