Role Of Neutron Transfer Research Articles

Role of neutron transfer in the reaction mechanism of 9Be+169Tm, 181Ta, 187Re and 197Au systems

The contribution of one neutron stripping cross section to the total reaction cross section has been studied for 9Be projectile incident on 169Tm, 181Ta, 187Re and 197Au targets around Coulomb barrier energy. The measured one neutron stripping cross sections for these systems have been compared with the coupled channel calculations. The recently developed global set of optical model potential parameters for 9Be projectile has been used in the present calculations. The cumulative of measured complete fusion (CF), incomplete fusion (ICF), one neutron stripping and calculated non-capture breakup (NCBU) cross sections is found to explain almost the reaction cross sections for all the targets. A very small contribution from target inelastic states and elastic breakup may contribute to the remaining part. The percentage fraction of cross section for CF, ICF, one neutron stripping, and NCBU over reaction cross section show the dominance of neutron transfer and NCBU at below barrier energies while CF and ICF processes have the major contribution at above barrier energies.

Role of neutron transfer in sub-barrier fusion

Fusion excitation function of $^{35}$Cl + $^{130}$Te system is measured in the energy range around the Coulomb barrier and analyzed in the framework of the coupled-channels approach. The role of projectile deformation, nuclear structure, and the couplings of inelastic excitations and positive Q$-$value neutron transfer channels in sub-barrier fusion are investigated through the comparison of reduced fusion excitation functions of $^{35,37}$Cl +$^{130}$Te systems. The reduced fusion excitation function of $^{35}$Cl + $^{130}$Te system shows substantial enhancement over $^{37}$Cl + $^{130}$Te system in sub-barrier energy region which is attributed to the presence of positive Q-value neutron transfer channels in $^{35}$Cl + $^{130}$Te system. Findings of this work strongly suggest the importance of +2$n$ - transfer coupling in sub-barrier fusion apart from the simple inclusion of inelastic excitations of interacting partners, and are in stark contrast with the results presented by Kohley \textit{et al.}, [Phys. Rev. Lett. 107, 202701 (2011)].

Barrier distribution from28Si+154Sm quasielastic scattering: Coupling effects in the fusion process

Barrier distribution for the 28 Si+ 154 Sm system has been extracted from large angle quasielastic scattering measurement to investigate the role of various channel couplings on fusion dynamics. The coupled channel calculations, including the collective excitation of the target and projectile, are observed to reproduce the experimental BD rather well. It seems that the role of neutron transfer, relative to collective excitation, is in fact weak in the 28 Si+ 154 Sm system even though it has positive Q-value for neutron transfer channels.

Analysis of the role of neutron transfer in asymmetric fusion reactions at subbarrier energies

The excitation functions were measured for the 28Si + 208Pb complete-fusion (capture) reaction at deep subbarrier energies. The results were compared with the cross sections predicted within the quantum diffusion approach. The role of neutron transfer in the case of positive Q values in the 28Si + 124Sn, 208Pb; 30Si + 124Sn, 208Pb; 20Ne + 208Pb; 40Ca + 96Zr; and 134Te + 40Ca complete-fusion (capture) reactions is discussed.

Role of neutron transfer in asymmetric fusion reactions at sub-barrier energies

The measured complete fusion (capture) excitation function is presented for the 28Si + 208Pb reaction at deep sub-barrier energies. This excitation function is compared with the one predicted with the quantum diffusion approach.

Nuclear reactions at near-barrier energies with quantum diffusion approach

The role of neutron transfer in the fusion (capture) reactions is discussed.

Fusion of the 6Li+120Sn and 7Li+119Sn and the role of neutron transfer and breakup processes

Excitation functions have been measured for the fusion of the weakly bound nuclei 6Li and 7Li respectively with 120Sn and 119Sn at energies around the Coulomb barrier by using an activation technique. With such a study we aim to investigate the role played by direct processes as neutron transfer and breakup on fusion. At energies above the barrier, the complete fusion cross section are lower than those predicted by fusion models. This suppression is independent of beam energy and is in agreement with the values reported in literature for heavier systems. At energies below the barrier, no significant enhancement due to the positive Q-value for one and two neutron transfer for the 7Li+119Sn system is observed as compared with the 6Li+120Sn.

Sub-barrier capture reactions with 16,18O and 40,48Ca beams

Various sub-barrier capture reactions with beams $^{16,18}$O and $^{40,48}$Ca are treated within the quantum diffusion approach. The role of neutron transfer in these capture reactions is discussed. The quasielastic and capture barrier distributions are analyzed and compared with the recent experimental data.

Effect of neutron transfer channels in fusion reactions with weakly bound nuclei at subbarrier energies

The role of neutron transfer in fusion reactions of weakly-bound nuclei at subbarrier energies is studied within the empirical model of channel coupling. The results from calculating the fusion cross sections for the 7Li + 209Bi, 9, 11Li + 208, 206Pb, 6, 7, 9, 11Li + 152Sm reactions are presented. Good agreement with the available experimental data is shown. Several combinations of colliding nuclei for which the strong enhancement of subbarrier fusion due to the effect of neutron transfer processes are predicted.

Erratum: Role of neutron transfer in capture processes at sub-barrier energies [Phys. Rev. C85, 024616 (2012)

Erratum: Role of neutron transfer in capture processes at sub-barrier energies [Phys. Rev. C<b>85</b>, 024616 (2012)

Role of neutron transfer in capture processes at sub-barrier energies

The role of neutron transfer with positive $Q$-value in sub-barrier capture reactions ${}^{132}$Sn,${}^{130}$Te+${}^{58,64}$Ni, and ${}^{60}$Ni+${}^{100}$Mo, measured recently by Z. Kohley et al. [Phys. Rev. Lett. 107, 202701 (2011)] and F. Scarlassara et al. [EPJ Web Conf. 17, 05002 (2011)], is studied and explained within the quantum diffusion approach. It is shown that the transfer of two neutrons influences the sub-barrier capture through the change of the deformations of the colliding nuclei. Based on our analysis, one can understand why the influence of the neutron transfer is strong in some capture reactions, but is weak in others.

Effect of neutron rearrangement on subbarrier fusion reactions

Abstract The role of neutron transfer is investigated in the fusion process near and below the Coulomb barrier within the empirical channel coupling approach. The possibility of neutron transfer with positive Q-values considerably increases the barrier penetrability. The enhancement of fusion cross sections for 58Ni + 64Ni, 32S + 64Ni, 40Ca + 48Ca, and 40Ca + 124Sn is well reproduced at subbarrier energies by the empirical channel coupling approach including the coupling to the neutron-transfer channels. The predictions of the fusion cross sections for several combinations of colliding nuclei are also proposed which may shed additional light on the effect of neutron transfer in fusion processes. A huge enhancement of deep subbarrier fusion probability was found for light neutron-rich weakly bound nuclei. This may be quite important for astrophysical primordial and supernova nucleosynthesis.

Role of neutron transfer and deformation effect in capture process at sub-barrier energies

The roles of nuclear deformation and neutron transfer in sub-barrier capture process are studied within the quantum diffusion approach. The change of the deformations of colliding nuclei with neutron exchange can crucially influence the sub-barrier fusion. The sub-barrier capture reactions following the neutron pair transfer are used for the indirect study of neutron-neutron correlation in the surface region of nucleus. The strong surface enhancement of the neutron pairing in nuclei 48 Ca, 64 Ni, and 116,124,132 Sn is demonstrated. Comparing the capture cross sections calculated without the breakup effect and experimental complete fusion cross sections, the breakup was analyzed in reactions with weakly bound projectiles 6,7,9 Li and 9 Be. A trend of a systematic behavior for the complete fusion suppression as a function of the target charge and bombarding energy is not achieved.

Sub-barrier fusion of neutron-rich nuclei and the role of neutron transfer and neutron-flow

We [Collaboration members include: F.J. Liang, D. Shapira, C.J. Gross, J.R. Beene, R.L. Varner, P.E. Mueller, A. Galindo-Uribarri, J. Gomez del Campo, D.W. Stracener, Physics Division ORNL, W. Loveland Oregon State Univ., H. Amro, J.J. Kolata Univ. of Notre Dame, J. Bierman Gonzaga Univ. A. L. Caraley State Univ. of New York at Oswego] have measured the formation of Evaporation Residues (ER) at near-barrier energies in collisions between several Te and Sn beams on 58 Ni and 64 Ni targets. The measured excitation functions are sparse but by measuring several systems we try to explore systematic trends in the sub-barrier cross section for ER formation. The data obtained show the expected enhancement in ER production (survival) with the addition of neutrons to the fused system. The overall cross sections, however, depend strongly on the capture cross sections that are the focus of this presentation An analysis of nucleus-nucleus capture in this mass region is attempted in the framework of a WKB formalism that incorporates neutron transfer/flow in a two-step process. The calculated capture cross sections are compared with the new, and other available data in this mass region. We use global potentials in our analysis and do not fit individual data sets but hope that these, or similar, calculations will provide a simple base for the prediction of trends in nucleus-nucleus capture cross sections.