Experimental study of the interactions on 7Li close to threshold

Physical Review C

An exclusive measurement of the breakup of 7 Li incident on a proton target was performed at 38.1 MeV (5.44 MeV/nucleon), probing the direct part of the excitation to the continuum. The two cluster constituents of 7 Li, 4 He, and 3 H, were recorded in coincidence in the MAGNEX spectrometer and a silicon detector respectively. Both detection systems were set at forward angles and the measurement of both kinematical solutions allowed the determination of a breakup angular distribution over a wide angular range in the center-of-mass frame. Comprehensive simulations provided the detection efficiency of the system and via the appropriate kinematics the transformation of the cross sections from the laboratory to the center-of-mass reference frame. The experimental results are analyzed and discussed together with previous elastic scattering data using the Continuum Discretized Coupled Channels (CDCC) framework and are found to be in satisfactory agreement. It was found that while the breakup cross section was dominated by the nonresonant component, the most important influence on the elastic scattering was due to coupling to the 7/2 − resonance of 7 Li.

arXiv: Atomic Physics, 2016

Absolute cross sections are measured for charge-exchange, ionization, and excitation within the same experimental setup for the Li$^{+}-$Ar, K$^{+}-$ Ar, and Na$^{+}-$ He collisions in the ion energy range $0.5-10$ keV. Results of our measurements along with existing experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes are realized with high probabilities and electrons are predominately captured in ground states. The cross section ratio for charge exchange, ionization and excitation processes roughly attains the value $10:2:1$, respectively. The contributions of various partial inelastic channels to the total ionization cross sections are estimated and a primary mechanism for the process is defined. The energy-loss spectrum, in addition, is applied to estimate the relative contribution of different inelastic channels and to determine the mechanis...

Nuclear Physics A, 1985

Cross sectmns for smgle-photonucleon emzsslons from 7LI have been measured for photon energies m the range 60-120 MeV by detecting the recodmg residual nuclet following excltatmn with bremsstrahlung radmtlon of end-point energtes 140 and 155 MeV Measurements of the 7Ll(e, 6L0e'p and 7Ll(e, 6He)e'n cross secUons were also made at the same electron energies A slgntficant ddterence between the ratto of electron-and bremsstrahlung-mduced yields for proton and neutron emtss~on is observed The results are compared to a too&fled quas~-deuteron model and a sample d~rect-knockout model in which recod terms are included

Pramana, 2009

The elastic scattering and the 6 He angular distributions were measured in 7 Li + 7 Li reaction at two energies, E lab = 20 and 25 MeV. FRDWBA calculations have been performed to explain the measured 6 He data. The calculations were very sensitive to the choice of the optical model potentials in entrance and exit channels. The one-step proton transfer was found to be the dominant reaction mechanism in 6 He production. Keywords. 7 Li( 7 Li, 6 He) reaction; E lab = 20 and 25 MeV; measured σ(θ); DWBA and CRC analysis. PACS Nos 25.70.Hi; 24.50.+g; 24.10.Eq

Zeitschrift f�r Physik A Hadrons and Nuclei, 1995

Angular distributions and excitation functions for the emission of a large number of proton, deuteron, triton, and a-particle groups in 7Li+ 160 reactions have been measured in the vicinity of the Coulomb barrier. Within the framework of the statistical reaction model, two approaches are presented that can reproduce the only weakly anisotropic shape of the angular distributions and the absolute cross section for those groups of ejectiles where contributions from direct reaction modes are small. When a standard Woods-Saxon potential deduced from elastic scattering is used, the entrance channel angular momentum distribution must be limited to values below critical angular momenta /cr which are smaller than the grazing angular momenta /gr if fusion is to be described. A global proximity potential with a parameter set that has been adjusted to reproduce the fusion reactions of a variety of p-and sd-shell nuclei yields very similar results when applied to 7Li+ I60. The proximity potential effectively introduces a similar angular-momentum limitation. This analysis proves the existence of a fusion cross section limitation and the importance of strong direct reaction modes (transfer and possibly inelastic processes) in 7Li + 160 reactions at energies close to and even below the Coulomb barrier. Another aspect of 7Li 4-160 is addressed briefly. The resonance-like structure observed in the heavy-ion radiative capture reaction 7Li(160, 70+1)23Na at Ex(23Na)=25.4MeV is not observed in the particle decay channels investigated in the present work.

Nuclear Physics A, 2016

The elastic scattering angular distributions for the system 7 Li + 64 Ni were measured in the bombarding energy range of 12 MeV ≤ E lab ≤ 26.4 MeV. A phenomenological optical model analysis was performed for the measured data. The strengths of the fitted potential components at the surface were estimated to extract their variation with energy. Further analyses of the measured angular distributions were performed with a hybrid potential composed of a renormalized folded real and a phenomenological imaginary potential. Both the model potentials predict similar energy dependent behavior for the effective interaction potential around the barrier. Unlike the heavy targets, 7 Li + 64 Ni does not show a normal threshold behavior. It also does not clearly exhibit a behavior similar to 6 Li + 64 Ni. The real potential for 7 Li + 64 Ni does not exhibit any significant energy dependence and the imaginary potential strength remains almost independent of energy above the Coulomb barrier (∼ 14 MeV). However, at energies below the barrier, a sudden drop in the imaginary potential strength is observed.

Nuclei in the Cosmos ( …, 2008

Physical Review C, 2020

The 7 Li(γ , t) 4 He ground state cross section was measured for the first time using monoenergetic γ rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror α-capture reactions 3 H(α, γ) 7 Li and 3 He(α, γ) 7 Be. Although over the last 30 years most measurements of the 3 H(α, γ) 7 Li reaction have concentrated in an energy range below E γ = 3.65 MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the 7 Li(γ , t) 4 He reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical S factor of 3 H(α, γ) calculated from the present data was fitted using the R-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated S factor agrees with the potential model calculation and lower energy experimental data.

Nuclear Physics B, 1973

For each K-p event, the charge exchange, AQ, is calculated, as the difference between the total charge of the forward going particles and of the incident K-meson. Taking all inelastic events, it is found that zero charge exchange does not dominate, occurring in only 40% of the cases. The proportion of AQ = + 1 is also 40%, while AQ =-1 and AQ = + 2 both represent about 10% of the events and other values of AQ are not important. The average charge exchange and the dispersion of AQ values are compared with the predictions of the multiperipheral and fragmentation models.

Physics Letters B, 2006

A search for the J π = 1/2 − spin-orbit partner of the J π = 3/2 − ground state in 7 He has been performed with the 7 Li(d, 2 He) chargeexchange reaction. The experimental results are incompatible with recent claims of such a state at very low excitation energy [M. Meister, et al., Phys. Rev. Lett. 88 (2002) 102501]. A decomposition of the spectrum is performed taking into account known resonances and quasifree charge-exchange reactions on 7 Li as well as on triton and 4 He clusters in the 7 Li ground state. A possible resonance at an excitation energy E x ≈ 1.45 MeV with a width Γ ≈ 2.0 MeV is suggested when the quasifree charge-exchange process on 7 Li is constrained by a measurement of the 6 Li(d, 2 He) reaction. Gamow-Teller strengths for transitions to the lowest states in 7 He deduced from the differential cross sections are in remarkable agreement with results from ab initio quantum Monte Carlo calculations.