Dominance of direct reaction channels at deep sub-barrier energies for weakly bound nuclei on heavy targets: The case B8+Pb208

2020 ◽  
Vol 102 (3) ◽  
Author(s):  
A. Pakou ◽  
L. Acosta ◽  
P. D. O'Malley ◽  
S. Aguilar ◽  
E. F. Aguilera ◽  
...  
Keyword(s):  
Direct Reaction ◽  
Weakly Bound ◽  
Reaction Channels

Analysis of fragment distribution and associated effects in 12,13C induced reactions

2014 ◽  
Vol 23 (05) ◽  
pp. 1450030
Author(s):  
Manpreet Kaur ◽  
Mahesh K. Sharma ◽  
Manoj K. Sharma
Keyword(s):  
Cross Sections ◽  
Heavy Ion ◽  
Evaporation Residue ◽  
Incomplete Fusion ◽  
Cluster Decay ◽  
Weakly Bound ◽  
Wide Range ◽  
Reaction Channels ◽  
Nice Agreement ◽  
Fragment Distribution

The decay of 220 Ra * nucleus formed in two different entrance channels 12 C +208 Pb and 13 C +207 Pb is investigated over a wide range of incident energies using the dynamical cluster decay model (DCM). The DCM is a non-statistical model used to account for the decay of hot and rotating nuclei formed in low energy heavy ion reactions. The excitation functions are calculated by considering quadrupole (β2) deformations with optimum orientations [Formula: see text] of decaying fragments. The DCM-based cross-sections for evaporation residue (ER), fusion–fission, αxn and neutron decay processes find nice agreement with the reported experimental data over wide range of incident energies. The cross-sections corresponding to different decay mechanism are worked out within DCM by fitting neck length parameter (ΔR). The entrance channel and angular momentum effects are investigated in reference to the above-mentioned reaction channels. In addition to this, the fragment mass distribution is worked out by colliding 13 C weakly bound stable projectile with a variety of target nuclei resulting in 13 C +159 Tb , 13 C +181 Ta and 13 C +207 Pb reactions. At comparable projectile energies, the increase in target mass is shown to favor asymmetric fragmentation in the fissioning region. Besides this, the incomplete fusion (ICF) contribution is worked out for 12 C and 13 C channels by applying necessary energy corrections in the framework of DCM.

Computational studies of gas-phase accretion product formation involving RO2

2020 ◽  
Author(s):  
Theo Kurtén ◽  
Siddharth Iyer ◽  
Vili-Taneli Salo ◽  
Galib Hasan ◽  
Matti Rissanen ◽  
...  
Keyword(s):  
Physical Chemistry ◽  
Gas Phase ◽  
Product Formation ◽  
Peroxy Radicals ◽  
Dimer Formation ◽  
Weakly Bound ◽  
Alkoxy Radicals ◽  
Reaction Channels ◽  
A Minor ◽  
Simple Systems

<p>Field and laboratory studies have indirectly but conclusively established that reactions involving peroxy radicals (RO<sub>2</sub>) play a key role in the gas-phase formation of accretion products, also commonly referred to as “dimers”, as they typically contain roughly twice the number of carbon atoms compared to their hydrocarbon precursors. Using computational tools, we have recently presented two different potential mechanisms for this process.</p><p>First, direct and rapid recombination of peroxy and alkoxy (RO) radicals, analogous to the recently characterized RO<sub>2</sub> + OH reaction, leads to the formation of metastable RO<sub>3</sub>R’ trioxides, which may have lifetimes on the order of a hundred seconds. [1] However, due to both the limited lifetime of the trioxides, and the low concentration of alkoxy radicals, the RO<sub>2</sub> + R’O pathway is likely to be a minor, though not necessarily negligible, pathway for atmospheric dimer formation.</p><p>Second, we have shown that recombination of two peroxy radicals – phenomenologically known to be responsible for the formation of ROOR’ – type dimers – very likely occurs through a multi-step mechanism involving an intersystem crossing (ISC). [2]  In contrast to earlier predictions, we find that the rate-limiting step for the overall RO<sub>2</sub>  + R’O<sub>2</sub> reaction is the initial formation of a short-lived RO<sub>4</sub>R’ tetroxide intermediate. For tertiary RO<sub>2</sub>, the barrier for the tetroxide formation can be substantial. However, for all studied species the tetroxide decomposition is rapid, forming ground-state triplet O<sub>2</sub>, and a weakly bound triplet complex of two alkoxy radicals. The branching ratios of the different RO<sub>2</sub> + R’O<sub>2</sub> reaction channels are then determined by a three-way competition of this complex. For simple systems, the possible channels are dissociation (leading to RO + R’O), H-abstraction on the triplet surface (leading to RC=O + R’OH), and ISC and subsequent recombination on the singlet surface (leading to ROOR’). All of these can potentially be competive with each other, with rates very roughly on the order of 10<sup>9</sup> s<sup>-1</sup>. For more complex RO<sub>2</sub> parents, rapid unimolecular reactions of the daughter RO (such as alkoxy scissions) open up even more potential reaction channels, for example direct alkoxy – alkyl recombination to form (either singlet or triplet) ether-type (ROR’) dimers.</p><p>[1] Iyer, S., Rissanen, M. P. and Kurtén, T. Reaction Between Peroxy and Alkoxy Radicals can Form Stable Adducts. Journal of Physical Chemistry Letters, Vol. 10, 2051-2057, 2019.</p><p>[2] Valiev, R., Hasan, G., Salo, V.-T., Kubečka, J. and Kurtén, T. Intersystem Crossings Drive Atmospheric Gas-Phase Dimer Formation. Journal of Physical Chemistry A, Vol. 123, 6596-6604, 2019.</p><p> </p>

Theoretical influence of third molecule on reaction channels of weakly bound complex CO2… HF systems

2006 ◽  
Vol 106 (7) ◽  
pp. 1640-1652 ◽  
Author(s):  
Shyh-Jong Chen ◽  
Cheng Chen ◽  
Yaw-Shun Hong
Keyword(s):  
Weakly Bound ◽  
Reaction Channels

scholarly journals Selection of different reaction channels in 6Li induced fusion reaction by a powerful combination of a charged particle array and a high-resolution gamma spectrometer

2018 ◽  
Vol 178 ◽  
pp. 03009
Author(s):  
G. X. Zhang ◽  
S. P. Hu ◽  
G. L. Zhang ◽  
H. Q. Zhang ◽  
Y. J. Yao ◽  
...  
Keyword(s):  
Ion Beam ◽  
Fusion Reaction ◽  
National Laboratory ◽  
Fusion Process ◽  
Weakly Bound ◽  
Proper Understanding ◽  
Particle Array ◽  
The Past ◽  
Reaction Channels ◽  
Selection Of

Investigation of the breakup and transfer effect of weakly bound nuclei on the fusion process has been an interesting research topic in the past several years. In comparison with radioactive ion beam (RIB), the beam intensities of stable weakly bound nuclei such as 6,7Li and 9Be, which have significant breakup probability, are orders of magnitude higher. Precise fusion measurements induced by these nuclei have already been performed. However, the conclusion of reaction dynamics was not clear and has contradiction. In order to have a proper understanding of the influence of breakup and transfer of weakly bound projectiles on the fusion process, the 6Li+89Y experiment with incident energies of 22 MeV and 34 MeV was performed on Galileo array in combination with Si-ball EUCLIDES at Legnaro National Laboratory (LNL) in Italy. Using the coincidence by the charged particles and γ-rays, the different reaction channels can be clearly identified.

scholarly journals Low energy reactions of halo nuclei

2021 ◽  
Vol 252 ◽  
pp. 04003
Author(s):  
Ismael Martel
Keyword(s):  
Coulomb Barrier ◽  
Reaction Mechanisms ◽  
Halo Nucleus ◽  
Low Energy ◽  
Halo Nuclei ◽  
Direct Reaction ◽  
Neutron Halo ◽  
Weakly Bound ◽  
The Core ◽  
Nuclear Core

Halo nuclei are extreme nuclear states consisting of one or more weakly-bound valence nucleons spatially decoupled from a tightly bound nuclear core. The weakly bound nature of the halo dominates the reaction probability, but the specific reaction mechanisms depend also on the core and target nuclei. Despite of the inherent complexity of the reaction process, simple two-body models and direct reaction theories can be used to extract useful information of the structure of the halo nucleus and its dynamics. These ideas are discussed using selected experiments of Coulomb barrier reactions with one- and two- neutron halo systems.

scholarly journals Density distribution effect on the analysis of the 6Li+ 58Ni reaction

2019 ◽  
Vol 17 (3) ◽  
Author(s):  
Fatemeh Torabi ◽  
Elí Francisco Aguilera Reyes
Keyword(s):  
Elastic Scattering ◽  
Density Distribution ◽  
Cross Sections ◽  
Optical Model ◽  
Density Variation ◽  
Polarization Potential ◽  
Direct Reaction ◽  
Weakly Bound ◽  
Density Distributions ◽  
Fusion Data

The effect of density variation on the optical-model (OM) analysis of 6Li + 58Ni is investigated by using bare potentials extracted from different density distributions of the weakly-bound 6Li nucleus. For each of the bare potentials, the real and imaginaru parts of the direct-reaction and fusion polarization potentials are deduced from respective X2 fittings to the elastic scattering and fusion data. The results obtained show that variations in the density distribution of the weakly-bound projectile can change the strengths of the dynamic direct-reaction polarization potential, however, it cannot make a noticeable difference on the OM predictions of fusion cross sections.

STRUCTURE EFFECTS IN COLLISIONS INDUCED BY HALO AND WEAKLY BOUND NUCLEI AROUND THE COULOMB BARRIER

2010 ◽  
Vol 19 (05n06) ◽  
pp. 1236-1240 ◽  
Author(s):  
V. SCUDERI ◽  
A. DI PIETRO ◽  
L. ACOSTA ◽  
F. AMORINI ◽  
M. J. G. BORGE ◽  
...  
Keyword(s):  
Cross Sections ◽  
Coulomb Barrier ◽  
Center Of Mass ◽  
Reaction Cross ◽  
Angular Distributions ◽  
Weakly Bound ◽  
Model Calculations ◽  
Center Of Mass Energy ◽  
Reaction Channels ◽  
Reaction Cross Sections

In this contribution, results concerning different reaction channels for the collisions induced by the three Be isotopes, 9,10,11 Be , on a 64 Zn target at energies around the Coulomb barrier will be presented. The experiments with the radioactive 10,11 Be beams were performed at REX-ISOLDE (CERN) whereas the experiment with the stable weakly bound 9 Be beam was performed at LNS Catania. Elastic scattering angular distributions have been measured for the three systems 9,10,11 Be + 64 Zn at the same center of mass energy. The angular distributions were analyzed with optical potentials and reaction cross sections were obtained from optical model calculations, performed with the code PTOLEMY. For the 11 Be + 64 Zn reaction, the break-up angular distribution was also measured.

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