6Li break-up effect on elastic and inelastic scattering of6Li +6Li at 156 MeV

The elastic and inelastic scattering of 156 MeV⁶Li projectiles from⁶Li is studied experimentally and theoretically. The experimental differential cross sections are analyzed by the method of coupled discretized continuum channels in which resonant and non-resonant break-up states of⁶Li are taken into account explicitly. The measured cross sections are simultaneously reproduced quite well by the calculations. Coupling effects of the break-up states are found to play an important role for the scattering.     

Single nucleon transfer reactions in6Li+6Li collisions at 156 MeV

Single nucleon transfer reactions in collisions of 156 MeV⁶Li ions with⁶Li nuclei, leading to unstable final nuclei (⁵Li,⁵He) have been experimentally studied. The measured⁶Li(⁶Li,⁷Li)⁵Li_gr and⁶Li(⁶Li,⁷Be)⁵He_gr differential cross sections have been analysed on the basis of a FR-DWBA procedure, looking to which extent the entrance channel optical potentials may account for the unknown exit channel potentials.     

Multibody final states of the 6Li + 6Li reaction AT 97 MeV

Absolute coincidence cross sections were measured for the reactions ⁶Li + ⁶Li → 3α, ⁶Li(⁶Li, 2α), and ⁶Li (⁶Li, 2d), where the latter two represent $\text{N-}\text{body}\text{(N ≧ 4)}$ final states. Broad peaks from the ⁶Li (⁶Li, 2α) reaction are well described by a double spectator pole (DSP) model utilizing a Hulthén wave function, whereas near 40 MeV the DSP peaks are much narrower than predicted. A broad peak in the 3α final-state spectrum, attributed to a single-spectator pole (SSP) process, is well described with the same wave function. The SSP is the principal mechanism for the 3α reaction, in contrast to data near 40 MeV which show that sequential decay from ⁸Be levels is dominant.     

Measurement of (p,n) and (n,p) reactions on 6Li and 7Li at 800 MeV

The measured ⁷Li(p,n), and ⁶Li(n,p) cross sections at 0° show a high-energy peak (≈25 MeV/c FWHM) which we attribute primarily to nuclear charge exchange leading to final states in ⁷Be, ⁶Be, and ⁶He, respectively. By contrast, the ⁷Li(n,p) cross section at O° shows a broad weak high-energy peak believed due mostly to break-up processes. At 16°, the ^6,7Li(n,p) cross sections are dominated by quasi-elastic scattering.     

The optical potential for 6Li-6Li elastic scattering at 156 MeV

Elastic scattering of ⁶Li from ⁶Li has been studied for a beam energy of 156 MeV. The experimental differential cross sections have been analysed on the basis of the optical model using various phenomenological forms. The spin-orbit interaction proves to be less significant. A semimicroscopic double-folding cluster model which generates the real part of the optical potential by an antisymmetrized dα cluster wave function of ⁶Li and αα, dd and dα interactions is well able to describe the experimental data.     

The 6Li(e,e′α) and 6Li(e,e′d) reactions at 520 MeV

The reactions ⁶Li(e,e′α) and ⁶Li(e,e′d) have been studied at T₀ ≈ 520 MeV and q ≈ 1.4 fm^?1, by coincidence measurements. The angular dependence of the cross sections is interpreted in the plane wave impulse approximation to obtain the momentum distribution of α-particle and deuteron clusters in ⁶Li. The amount of clustering of ⁶Li is also discussed.     

Analysis of (6Li,d) and (d, 6Li) reactions in the nickel and tin regions

The (⁶Li, d) and (d, ⁶Li) L = 0 transitions in the mass regions $\text{A ? 60}\text{and}\text{A ? 116}$ are analyzed utilizing microscopic form factors. The cross sections follow the pattern given by the two-proton and two-neutron transfer cross sections.     

Cross sections for the 11.08 (3+) and 11.096 MeV (4+) states in 16O by 12C(6Li,d) and 13C(6Li,t)

Particle and particle-γ measurements were performed to determine the cross sections for population of the 8.87 (2^?), 10.35 (4⁺), 11.08 (3⁺) and 11.096 MeV (4⁺) states in ¹⁶O by the ¹²C(⁶Li, d) and ¹³C(⁶Li, t) reactions in the energy range from 20—34 MeV. In general, statistical compound nuclear calculations correctly predict the magnitude of the cross sections of the unnatural parity states and underpredict those for the natural parity states. The population of the 10.35 MeV 4⁺ state in the ¹³C(⁶Li, t) reaction is correctly predicted by these calculations. These measurements support earlier claims that the large ¹²C(⁶Li, d) cross section to the 11.096 MeV 4⁺ state is a result of multistep processes.     

Cross section of the reaction 6Li(p, γ)7Be

The cross section of the reaction ⁶Li(p, γ)⁷Be has been measured using Ge(Li) γ-ray spectrometers for proton bombarding energies E_p from 200 keV to 1200 keV. At E_p = 800 keV, the total (p, γ) integrated cross section is found to be 3.1 ± 0.4 μb. The cross section adopted from consideration of this and previous measurements is in good agreement with that predicted from the known thermal neutron cross section for ⁶Li(n, γ)⁷Li on the assumption that properties of mirror direct capture reactions can be well described by optical potentials that use the same parmeter values for the two reactions.     

Neutron total and scattering cross sections of 6Li in the low-MeV range

Neutron total cross sections of ⁶Li are measured at intervals of ? 10 keV from ≈ 0.1 to 4.8 MeV with precisions of ≈ 1 to 3 %. Differential elastic scattering cross sections are measured at intervals of ? 100 keV from 1.5 to 4.0 MeV at 10 or more scattering angles distributed between ≈ 20 and 160 deg. Differential inelastic scattering cross sections are measured at selected angles in the energy range 3.5 to 4.0 MeV. The experimental results are analyzed in terms of R-matrix theory and the model parameters used to deduce the ${}^6\text{Li(n}\text{,α)}$ cross sections. The implications of the measurements and their interpretation on the level structure of ⁷Li and the reaction mechanisms are discussed.     

Deuteron exchange mechanism for the6Li(n, α) reaction at low energies

It is proposed that the major part of the low energy (l/v)⁶Li(n, α)³H cross section may be explained as being due to a direct deuteron exchange mechanism. This proposal is in agreement with recent experimental data on the spin-dependent⁶Li(n, α) cross section; it may be used to extract information on the⁶Li-αd vertex constant. The importance of the assumption of ad-exchange process for the⁶Li(n, α) angular distribution is discussed in the framework ofS-matrix theory.     

Direct and compound nuclear contributions to the 13C(6Li,t) reaction at Elab = 25 MeV

The reaction ¹³C(⁶Li, t)¹⁶O has been studied in the incident energy range 24–26 MeV. Complete angular distributions have been measured at E_⁶Li, = 25 MeV in the angular range θ_lab = 8°–172°, with the reaction ⁶Li(¹³C, t)⁶O being used for the backward angle measurements. Cross sections for evaporation residues from the fusion of the ⁶Li + ¹³C system have been measured in the incident ⁶Li energy range 9.2–35.1 MeV. Compound nuclear contributions to the transfer cross sections have been calculated using the Hauser-Feshbach statistical theory with the assumption that the compound-nucleus formation cross section is equal to the measured fusion cross section. By comparison of the compound nuclear calculations with backward angle data it is found that the sharp cutoff approximation commonly used to represent the initial angular momentum distribution of the compound nucleus is not adequate for the ¹³C(⁶Li, t)¹⁶O reaction. Good fits to the backward angle data can be obtained by using a smooth cutoff approximation. The forward angle cross sections have been compared with exact finite-range distorted-wave Born approximation calculations to extract transferred angular momenta and spectroscopic strengths. The present results differ from those of an earlier study. These differences are due to the inclusion of forward angle data in the present study.     

Folding model analysis of pion elastic and inelastic scattering from 6Li and 12C

π ^±-Nucleus scattering cross sections are calculated applying the Watanabe superposition model with a phenomenological Woods-Saxon potential. The phenomenological potential parameters are searched for π ^± scattering from ⁶Li and ¹²C to reproduce not only differential elastic cross sections but also inelastic and total and reaction cross sections at pion kinetic energies from 50 to 672 MeV. The optical potentials of ⁶Li and ¹²C are calculated in terms of the alpha particle and deuteron optical potentials. Inelastic scattering has been analyzed using the distorted waves from elastic-scattering data. The values of deformation lengths thus obtained compare very well with the ones reported earlier.     

Excitation functions of191+193Ir,197Au(6Li,xn+yp) compound nuclear reactions at ELi=48–156 MeV

Excitation functions of the compound nuclear reactions^191+193Ir,¹⁹⁷Au(⁶Li,xn+yp) forx =3–13 andy=0–2 have been investigated by means of in-beamγ-ray spectroscopy at the 156 MeV⁶Li beam of the Karlsruhe Isochronous Cyclotron. The beam energy has been varied in the range of 48 to 156 MeV in steps of about 10 MeV by Be-absorber foils in the external beam line. Absolute cross sections have been determined by normalizing the measuredγ-ray intensities to the production cross sections ofK- X-rays in the target. The experimental excitation functions are discussed on the basis of predictions of the preequilibrium (hybrid) model. While in most cases the theoretical calculations fairly well reproduce energy position and shapes of the curves, strong discrepancies in the absolute scale of the cross sections are observed. The theoretical predictions overestimate the (⁶Li,xn) cross sections by a factor of about 6. Conspicuous anomalies have been detected when comparing the (⁶Li, xn+1(2)p) reactions with (⁶Li,xn) reactions. The reactions with emission of one or two protons are considerably enhanced. The discrepancies and anomalies observed are tentatively explained by the influence of direct reaction channels as the⁶Li break-up, which experimentally proved to be the dominant contribution to the total reaction cross section. The enhancement of the reactions with emission of protons may be a consequence of transfer reactions into highly excited states combined with compound nucleus formation thus implying a cluster effect in preequilibrium emission process.     

Elastic scattering of 86 MeV9Li and 55 MeV6He on208Pb

The cross sections of elastically scattered⁹Li and⁶He on²⁰⁸Pb were measured. The scattered particles were detected by an annular CR-39 solid state nuclear track detector and the monitoring was done with a triple telescope of silicon detectors. The classical and optical model analyses of the measured elastic cross sections have been carried out. It was shown that the peripheral⁹Li interaction region has a rather high transparency. Strong dynamical polarization of⁹Li ions in the process of scattering is suggested.     

Quasi-elastic electron scattering (e,e′p) and (e,e′d) from 6Li in a coincidence experiment

Coincidence cross sections for the reactions ⁶Li(e, e′p) and ⁶Li(e, e′d) have been measured in the region of quasi-elastic scattering. Using incident electrons of 2.5 and 2.7 GeV, the four-momentum transfers to the proton were 6.6 fm^?2, 10.0 fm^?2 and 11.6 fm^?2. The proton coincidence data agree with shell-model distributions assuming a Woods-Saxon potential and including short-range nucleon-nucleon correlations. The best fit to the deuteron coincidence data is obtained with a cluster wave function for the p-nucleons and a harmonic oscillator wave function for the s-nucleons taking into account the deuteron yield from the s-shell. The ratio of the deuteron cross section from ⁶Li divided by the elastic e-d scattering cross section depends only slightly on the four-momentum transfer and has a value of ≈ 2.     

High-energy electron scattering on 6Li and 12C as an incoherent superposition of single-nucleon processes

High-energy electro-excitation cross sections on ⁶Li and ¹²C in the region of the first nucleon resonance are compared with calculations in the impulse approximation. It is shown that the ⁶Li and ¹²C cross sections can be reproduced by an incoherent superposition of nucleon structure functions for 0.2<Q²<0.4 GeV² and primary energies in the GeV range.     

Elastic scattering of6Li on6Li in the energy rangeE CM=2–10MeV

In a coincidence experiment, two excitation functions (0_cm=60° and 90°) and four angular distributions of the differential cross section for the elastic scattering of⁶Li on⁶Li were measured. The energy range for the excitation functions was from 2 to 10 MeV (CM), the angular distributions were taken at CM-energies of 4, 5, 6, 7.25 MeV. Optical model calculations were performed. It is shown that the outer portion of the potentials is most important for reproducing the experimental data.     

Peculiarities in total cross sections of reactions with weakly bound nuclei <Superscript>6</Superscript>He, <Superscript>9</Superscript>Li

The energy dependence of the total cross sections for the ⁶He + Si and ⁹Li + Si reactions was measured at beam energies between 5 and 20 MeV per nucleon. The results agree with experimental data published for the ⁶He + Si reaction. New data are obtained for the ⁹Li + Si reaction in the vicinity of a local enhancement of the total cross section. A theoretical analysis of the possible reasons behind the appearance of this peculiarity in the case of collisions of ⁶He and ⁹Li nuclei with silicon target nuclei is performed. In particular, the enhancement may owe its origin to the effect of loosely bound projectile nucleons.     

Direct and resonant capture observed in the 3H(τ,γ)6 Li reaction

A direct capture model is used to calculate the ³H(τ, γ)⁶ Li cross section. The result for the ground-state cross section is in very good agreement with the data. The calculation for the cross section for the first excited state is in good agreement with the shape and angular dependence of the measured cross section at lower energies. Above E_τ=10 MeV a large discrepancy indicates a non-direct contribution. This is interpreted as a resonance in the compound nucleus ⁶Li with a configuration other than ${}^3\text{He}\text{+}{}^3\text{H}$.