Direct Breakup Research Articles

Due consideration of the breakup and direct reaction mechanisms within (d, p), (d, 2p), (d, xn2p), and (d, xn) reactions

Suitable account of available excitation-function of deuterons interaction with target nuclei components of candidates materials for the ITER fusion reactor, the European DEMO fusion reactor, and the IFMIF-DONES Irradiation Facility has been proved by consistent analysis of the reaction mechanisms involved in the complex deuteron-nucleus interaction. In this work the attention has been focused on the analysis of the deuteron activation cross sections related to the gas accumulation, (d, p), (d, 2p), (d, xn2p), and to the strong neutron emission, (d, xn), interaction processes of interest for the radiation damage and shielding design studies devoted to the structural materials selection. The key role of direct interactions, i.e., breakup, stripping and pick-up processes is stressed out by the comparison of data with theoretical and evaluation predictions.

Dating in a digital world: The role of pathological personality traits in psychological reactions to direct and ambiguous rejection

Ghosting is a type of interpersonal rejection involving a unilateral communication interruption without explanation, using technological channels. Vulnerable narcissism and borderline traits can increase sensitivity to interpersonal rejection and reduce tolerance to ambiguity, whereas grandiose narcissism is related to low rejection sensitivity. Yet, the influence of narcissism and borderline on responses to ghosting is unexplored. We examined the influence of pathological personality traits on psychological reactions to direct breakup and ghosting (i.e., ambiguous breakup) in a sample of 604 young adults (mean age = 22.4 ± 2.74). After measuring borderline and narcissistic traits (grandiose and vulnerable), participants were randomly assigned to one of two scenario-based conditions: direct breakup or ghosting events. Negative emotions and state paranoia were assessed after the experimental manipulation. Participants experienced greater negative emotions and state paranoia in the ghosting condition compared to direct breakup. Individuals high in vulnerable narcissism and borderline traits anticipated higher negative emotions and state paranoia. Grandiose narcissism was unrelated to such reactions. Unexpectedly, pathological personality traits did not moderate the effect of breakup ambiguity on individuals' psychological reactions. Findings suggest that the impact of pathological personality traits is reduced in front of such a socially painful stimulus as an ambiguous rejection.

Experimental evidence for α production following neutron transfer in the C13 + Nb93 system

Spectra of $\ensuremath{\alpha}$ particles were measured for $^{12,13}\mathrm{C} + ^{93}\mathrm{Nb}$ systems at several angles for a bombarding energy of 65 MeV to investigate various reaction mechanisms like direct break up and cluster transfer responsible for $\ensuremath{\alpha}$ production. The $\ensuremath{\alpha}$ spectra were analyzed in detail to determine the effect of $1n$ transfer on an $\ensuremath{\alpha}$-production cross section in particular. After accounting for contributions from direct breakup and Be transfer, there is a clear signature of the $\ensuremath{\alpha}$ particles produced through the break-up process following neutron transfer in the case of a $^{13}\mathrm{C}$ induced reaction. This is an interesting result being reported for the strongly bound projectile.

Continuum Strength of Direct Breakup Induced by External Isoscalar Field

Continuum Strength of Direct Breakup Induced by External Isoscalar Field

Extended Migdal-Watson formula to evaluate background strength in binary breakup reactions

A new formula to evaluate the nonresonant background for binary breakup is proposed by extending the Migdal-Watson (MW) formula, which was originally developed for $s$-wave breakup in charge neutral systems. The strength of the direct breakup, which is assumed by a one step transition from the initial bound state, is simulated by the complex scaling method (CSM) in binary cluster systems. The extended MW formula is applied to the direct breakup of $^{20}\mathrm{Ne}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\alpha}+^{16}\mathrm{O}$, and we have found that the formula nicely reproduces the strength of the direct breakup evaluated by CSM. We have demonstrated that new parameters introduced in the extended MW formula have a close connection to the spatial size of the initial wave packet, which is given by the product of the initial wave function and the external field. The application of the new formula to the direct breakup of $^{12}\mathrm{Be}$ into $\ensuremath{\alpha}+^{8}\mathrm{He}$ is also discussed.

A clear signature of the breakup modes for 9Be on a proton target at 5.6 MeV/nucleon

The breakup of 9Be is studied via an inelastic scattering experiment on a proton target at 5.6 A MeV in inverse kinematics. Two of the three cluster constituents (α and α) as well as the proton target recoil were recorded in a triple coincidence mode allowing a full kinematics approach analysis. In this respect relative α - α and α - n, Q-value and 9Be excitation spectra, energy spectra for all fragments as well as the energy spectrum of the recoil proton were reconstructed. A clear signature of the two breakup sequential modes (5He + 4He and 8Be + n) was identified via the recoiling proton reconstructed spectra together with the direct breakup decay. A strong 5He + 4He mode was observed compatible with previous beta decay experiments.

Direct and resonant breakup of radioactive Be7 nuclei produced in the Sn112(Li6,Be7) reaction

Cross sections for direct and resonant breakup of radioactive $^{7}\mathrm{Be}$ nuclei produced in a transfer reaction $^{112}\mathrm{Sn}(^{6}\mathrm{Li},^{7}\mathrm{Be}\ensuremath{\rightarrow}\ensuremath{\alpha}+^{3}\mathrm{He})\phantom{\rule{0.16em}{0ex}}^{111}\mathrm{In}$ have been measured. Breakup of $^{7}\mathrm{Be}$ into $\ensuremath{\alpha}$ and $^{3}\mathrm{He}$ cluster fragments via its resonant states of $7/{2}^{\ensuremath{-}}$(4.57 MeV) and $5/{2}^{\ensuremath{-}}$ (6.73 MeV) in the continuum have been identified for the first time using the measured distribution of $\ensuremath{\alpha}\text{\ensuremath{-}}^{3}\mathrm{He}$ relative energy and the reaction $Q$ value obtained from the $\ensuremath{\alpha}\text{\ensuremath{-}}^{3}\mathrm{He}$ coincident events. The breakup cross sections extracted from the efficiency corrected coincidence yield compares well with the results of the coupled-channels calculations. Significant cross sections for breakup of $^{7}\mathrm{Be}$ into its cluster fragments directly or through resonant states highlight the importance of the ground-state structure of $^{7}\mathrm{Be}$ as a cluster of $\ensuremath{\alpha}$ and $^{3}\mathrm{He}$.

Consistent analysis of deuteron interactions at low and medium energies

An extended discussion of the deuteron-induced reactions concerning full parametrization procedure as well as consideration of the theoretical models associated to the deuteron interaction process is carried out. The key role of direct interactions, i.e., breakup, stripping and pick-up processes is stressed out by comparison of the available experimental data with theoretical and evaluation predictions.

Breakdown of the Coulomb-explosion imaging technique induced by the ultrafast rotation of fragments

Coulomb-explosion imaging is a broadly employed technique to reconstruct the geometry of molecules from the direct multibody breakups of its ions. However, we reveal that this technique fails for a large class of systems, such as (${\mathrm{CO})}_{2}{}^{3+}$ and ${\mathrm{ArCO}}^{3+}$, since the events of the ``direct breakup channel'' are not the real direct breakups but the rapid sequential breakups with a short-lived and ultrafast-rotational fragment. Using Ar-CO as a prototype, we have investigated theoretically its Coulomb-explosion process. We find that due to the interfield between the metastable ${\mathrm{CO}}^{2+}$ and ${\mathrm{Ar}}^{+}$, ${\mathrm{ArCO}}^{3+}$ changes from its initial T shape into the more stable linear shape within 100 fs; such a rotation of ${\mathrm{CO}}^{2+}$ is hundreds of times faster than the field free case. Further, the advanced three-body surface hopping simulations indicate that the angle ${\ensuremath{\angle}}_{(\mathrm{Ar},\mathrm{CO})}$ has rotated from an initial ${95}^{\ensuremath{\circ}}$ to $110.6{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}$ on average before the Coulomb explosion, which agrees well with the one (${115}^{\ensuremath{\circ}}$) detected by Gong et al. [Phys. Rev. A 88, 013422 (2013)]. Furthermore, we point out that correct geometry of ArCO can be obtained from the three-body breakups with high kinetic-energy release ($>20$ eV).

Analysis of empirical parametrization and microscopical studies of deuteron-induced reactions

A review of deuteron-induced reaction analyses is carried out paying due consideration to reaction cross-section parametrization as well as theoretical models associated to the deuteron interaction process. The key role of direct interactions, i.e., breakup, stripping and pick-up processes is stressed out by the comparison of data with theoretical and evaluation predictions, including the latest TENDL-2017 library.

Role of target shell structure in direct reactions involving weakly bound Li7

The effect of the shell structure of the target nuclei ($^{89}\mathrm{Y}$ and $^{93}\mathrm{Nb}$) on reaction mechanisms involving the weakly bound $^{7}\mathrm{Li}$ projectile has been investigated via a comparative study of different processes. Measurements of direct breakup, nucleon transfer leading to the ejectile in bound as well as unbound states, and elastic scattering have been carried out for the $^{7}\mathrm{Li}+^{89}\mathrm{Y}$ system at three different energies near the Coulomb barrier. An extensive analysis of this comprehensive data set was carried out using coupled channel calculations and compared with a previous similar study for the $^{7}\mathrm{Li}+^{93}\mathrm{Nb}$ system. The observed cross sections at low target excitations for nucleon transfer reactions correlate with the vacancies in the valance orbitals.

Role of cluster structure in the breakup of Li7

Direct and sequential breakups of the projectile in the $^{7}\mathrm{Li}+^{112}\mathrm{Sn}$ reaction have been measured at a beam energy of 30 MeV. Cross sections for sequential breakup of $^{7}\mathrm{Li}$ into $\ensuremath{\alpha}$ and $t$ cluster fragments via its second resonant state of $5/{2}^{\ensuremath{-}}$ (6.68 MeV) in the continuum have been measured for the first time along with the first resonant state ($7/{2}^{\ensuremath{-}}$, 4.63 MeV). Probabilities of sequential breakup proceeding through $\ensuremath{-}1n$ and $\ensuremath{-}2n$ transfer channels, i.e., ($^{7}\mathrm{Li},^{6}\mathrm{Li}$) and ($^{7}\mathrm{Li},^{5}\mathrm{Li}$) reactions followed by breakup, into $\ensuremath{\alpha}+d$ and $\ensuremath{\alpha}+p$, respectively, were found to dominate over $\ensuremath{\alpha}+t$ breakup. Measured cross sections for the above breakup channels and elastic scattering have been compared with coupled-channel calculations to understand the reaction mechanism involving the weakly bound projectile $^{7}\mathrm{Li}$. Significant cross section for direct breakup of $^{7}\mathrm{Li}\ensuremath{\rightarrow}^{6}\mathrm{He}+p$ has also been measured for the first time, indicating the importance of the new ($^{6}\mathrm{He}+p$) cluster configuration that may be necessary to understand the complete structure of $^{7}\mathrm{Li}$ and its energy levels.

Three-body effects in the Hoyle-state decay

We use a sequential R-matrix model to describe the breakup of the Hoyle state into three α particles via the ground state of Be8. It is shown that even in a sequential picture, features resembling a direct breakup branch appear in the phase-space distribution of the α particles. We construct a toy model to describe the Coulomb interaction in the three-body final state and its effects on the decay spectrum are investigated. The framework is also used to predict the phase-space distribution of the α particles emitted in a direct breakup of the Hoyle state and the possibility of interference between a direct and sequential branch is discussed. Our numerical results are compared to the current upper limit on the direct decay branch determined in recent experiments.

Effects of unconventional breakup modes on incomplete fusion of weakly bound nuclei

The incomplete fusion dynamics of $^6$Li + $^{209}$Bi collisions at energies above the Coulomb barrier is investigated. The classical dynamical model implemented in the {\sc platypus} code is used to understand and quantify the impact of both $^6$Li resonance states and transfer-triggered breakup modes (involving short-lived projectile-like nuclei such as $^8$Be and $^5$Li) on the formation of incomplete fusion products. Model calculations explain the experimental incomplete-fusion excitation function fairly well, indicating that (i) delayed direct breakup of $^6$Li reduces the incomplete fusion cross-sections, and (ii) the neutron-stripping channel practically determines those cross-sections.

Influence of breakup on elastic and α-production channels in the 6Li+ 116Sn reaction**One of the authors (SM) would like to thank DAE-BRNS for financial assistance through a major research project. This work is supported by National Natural Science Foundation of China (U1432247, 11575256, U1632138, 11605253) and China Postdoctoral Science Foundation (2016M602906)

The effects of breakup reactions on elastic and α-production channels for the 6Li+116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle production differential cross sections have been obtained at several projectile energies between 22 and 40 MeV. The measured breakup α-particle differential cross sections and elastic scattering angular distributions have been compared with the predictions of continuum-discretized coupled channels (CDCC) calculations. The influence of breakup coupling has also been investigated by extracting dynamic polarization potentials (DPP) from the CDCC calculations. From the predictions of CDCC calculations the relative importance of the nuclear, Coulomb, and total breakup contributions have also been investigated. The nuclear breakup couplings are observed to play an important role in comparison to the Coulomb breakup for the direct breakup mechanisms associated in the reaction of 6Li projectile with 116Sn target nuclei. The influence of strong nuclear breakup coupling exhibits suppression in the Coulomb-nuclear interference peak. The direct breakup cross sections from the CDCC calculations under-predict the measured α-particle differential cross sections at all energies. This suggests that the measured α particles may also have contributions from other possible breakup reaction channels.

Ground-state configuration of neutron-rich Al35 via Coulomb breakup

The ground-state configuration of Al-35 has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of similar to 403 MeV/nucleon. The measured inclusive differential CD cross section for Al-35, integrated up to 5.0 MeV relative energy between the Al-34 core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of 34Al is 29(7) mb. The differential CD cross section of Al-35 -> Al-34 + n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of Al-35 could be, tentatively, 1/2+ or 3/2(+) or 5/2(+). The valence neutrons, in the ground state of Al-35, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the Al-34 core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N = 20,28 which suggests narrowing the magic shell gap. If the 5/2+ is the ground-state spin-parity of Al-35 as suggested in the literature, then the major ground-state configuration of Al-35 is a combination of Al-34(g. s.; 4(-)) circle times upsilon(p3/2) and Al-34(isomer; 1(+)) circle times upsilon(d3/2) states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.

Cluster structure effects of projectile in7Li+208Pb reaction

Inclusive and exclusive cross sections have been measured for different projectile breakup channels. It is observed that the inclusive cross sections are larger than the exclusive ones. It is found that other processes, besides the direct breakup channel, significantly contribute to the inclusive channels. A clear α+x cluster structure has been found from coincidence data.

Breakup of Li6+p at near-barrier energies and the effect on elastic scattering

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.

Coulomb breakup of neutron-rich 29,30Na isotopes near the island of inversion

First results are reported on the ground state configurations of the neutron-rich 29,30Na isotopes, obtained via Coulomb dissociation (CD) measurements. The invariant mass spectra of these nuclei have been obtained through measurement of the four-momenta of all decay products after Coulomb excitation of those nuclei on a 208Pb target at energies of 400–430 MeV/nucleon using the FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated inclusive CD cross-sections (CD) of 89 (7) mb and 167 (13) mb for one neutron removal from 29Na and 30Na, respectively, have been extracted up to an excitation energy of 10 MeV. The major part of one neutron removal, CD cross-sections of those nuclei populate the core, in its ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of 29Na and 30Na is the d-orbital with a small contribution from the s-orbital, which are coupled with the ground state of the core. One of the major components of the ground state configurations of these nuclei are 28Na and 29Na, respectively. The ground state spin and parity of these nuclei obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the s and d orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with shell model calculation using the MCSM suggests a lower limit of around 4.3 MeV of the sd–pf shell gap in 30Na.

Role of the direct processes in low-energy deuteron interactions

An extended analysis of the key role of direct interactions, i.e., breakup, stripping and pick-up processes, has been carried out for deuteron-induced reactions. Particular comments concern the deuteron breakup which is the dominant mechanism involved in surrogate reactions on heavy nuclei, around the Coulomb barrier.