Total Reaction Cross Sections σR Research Articles

Study of α+32S scattering using different potentials at 386 MeV

Elastic and inelastic scattering of α-particles from 32S has been theoretically studied at Elab = 386 MeV using three different potentials. For this, the phenomenological Woods–Saxon parameterized potential, single folding cluster potential, and the high-energy approximation model have been used. The results of our calculations have been compared with the experimental differential cross sections obtained from previously measured angular distributions. Our method of calculations successfully reproduces the experimental data. The values of the total reaction cross-section σR as well as the deformation parameters have been calculated and compared with those available in the literature.

Total reaction cross sections of neutron-rich light nuclei measured by the COMBAS fragment-separator

Preliminary results of measurements of the total reaction cross sections σR for nuclei 4He, 6He, 8He, 7Li, 8Li, 9Li, 1Li, 11Be, 9Be, 10Be, 11Be, 12Be, 8B, 10B, 11B and 12B nuclei at energy range (10-50) A MeV with 28Si target is presented. The secondary beams of light nuclei were produced by bombardment of the 15N (50 A MeV) primary beam on Be target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 600 μm Al was installed. The Bρ of the second section of the fragment-separator was adjusted for measurements in energy range (10-45) A MeV. The strong absorption model reproduces the A-dependence of ψR, but not the detailed structure. We are comparing our experimental data with predictions of microscopic (dashed line) and strong absorption model, Glauber multiple scattering theory and preliminary results are obtained.

Total reaction cross sections and neutron-removal cross sections of neutron-rich light nuclei measured by the COMBAS fragment-separator

Preliminary results of measurements of the total reaction cross sections σR and neutron removal cross section σ-xn for weakly bound 6He, 8Li, 9Be and 10Be nuclei at energy range (20-35) A MeV with 28Si target is presented. The secondary beams of light nuclei were produced by bombardment of the 22Ne (35 A MeV) primary beam on Be target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 200 μm Al was installed. The Bρ of the second section of the fragment-separator was adjusted for measurements in energy range (20-35) A MeV. Two-neutron removal cross sections for 6He and 10Be and one –neutron removal cross sections 8Li and 9Be were measured.

Total reaction cross sections measurement for 6,8He and 8,9Li nuclei with energies of (25–45)/A MeV on natAl and natPb

Preliminary results of measurements of the total reaction cross sections σR for weakly-bound 6,8He and 8,9Li nuclei at energy range (25–45)/A MeV on 27Al and 208Pb targets are presented. The secondary beams of 6,8He and 8,9Li were produced by bombardment of the 11B (33 A MeV) primary beam on Be (89 mg cm–2) target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 200 μm Al was installed. The Bρ of the second section of the fragment-separator was adjusted for measurements in energy range (25–45)/A MeV. The secondary products were detected by a telescope consisting of two Si ΔE detectors 300, 1000 μm and E-detector, which consisted of nine CsI/Tl granules.

Total reaction cross section from the interaction of 4He ions with 28Si at 10–30 MeV

New results have been obtained for the energy dependence of the total reaction cross section σR of 4He on 28Si in the energy range Eα ≤ 30 meV.

Calculation of Total Reaction Cross Sections Induced byIntermediate Energy α-Particles with theBoltzmann-Uehling-Uhlenbeck Model

The Boltzmann-Uehling-Uhlenbeck (BUU) model, which includes theFermi motion, the mean field, individual nucleon-nucleon (N-N)interactions and the Pauli blocking effect, etc., is used tocalculate the total reaction cross section σR induced byα-particles on different targets in the incident energyrange from 17.4 to 48.1 MeV/u. The calculation result can wellreproduce the experimental data. The nucleus-nucleus interaction radius parameter r0 was extracted from experimentalσR. It is found that r0 becomes constant withthe increasing mass number of target.

Total Reaction Cross Section in an Isospin-Dependent QuantumMolecular Dynamics Model

The isospin-dependent quantum molecular dynamics (IDQMD) model is usedto study the total reaction cross section σR. Theenergy-dependent Pauli volumes of neutrons and protons have beendiscussed and introduced into the IDQMD calculation to replace thewidely used energy-independent Pauli volumes. The modified IDQMDcalculation can reproduce the experimental σR well for bothstable and exotic nuclei induced reactions. Comparisons of thecalculated σR induced by 11Li with different initialdensity distributions have been performed. It is shown that thecalculation by using the experimentally deduced density distributionwith a long tail can fit the experimental excitation function betterthan that by using the Skyrme-Hartree-Fock calculated density withoutlong tails. It is also found that σR at high energy is sensitiveto the long tail of density distribution.

The nature and reactions of halo nuclei

Absolute differential cross sections for elastic p 4He, p 6He and p 8He small-angle scattering were measured in inverse kinematics with secondary 4,6,8He-beams at an energy near 0.7 GeV/u. The experiment was performed using beams from the heavy-ion synchrotron SIS and the fragment separator FRS of GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. Projectile scattering angles were measured with multi-wire tracking detectors. For proton scattering from the neutron-rich isotopes 6He and 8He, differential elastic-scattering cross sections dσ/dt were deduced in the range 0.002⩽|t|⩽0.05 (GeV/c)2 of the four-momentum transfer squared t. For elastic p 4He scattering, the data obtained in the t-range 0.002⩽|t|⩽0.02 (GeV/c)2 supplement the results from an earlier work performed in direct kinematics. From the differential cross sections the integral elastic-scattering cross sections σel, the total cross sections σtot, and the total reaction cross sections σr for the proton–nucleus strong interaction were evaluated. The data obtained on dσ/dt allow the radial matter distributions in the 6He and 8He nuclei to be determined and the corresponding root-mean-square matter radii to be deduced.

MEASUREMENT OF TOTAL REACTION CROSS SECTIONFOR EXOTIC LIGHT PROTON-RICH NUCLEUS 12N

Measurements of the total reaction cross section for proton drip line nucleus 12N at about 50.4 MeV/u on Si target were performed on RIBLL. Compared with its neighbor 13N, large enhancement of total reaction cross section σr for 12N is observed. This might be caused by nuclear deformation and nucleon pair effect, and the experimental inaccuracy should not be neglected. The σr of 12N calculated by using a microscopic Glauber model is in agreement with the experimental results.

Analysis of the12C+12C inelastic scattering in the energy range 11?24 MeV/n

Elastic and inelastic scatterings cross-sections of12C+12C in the energy range 11–24 MeV/n have been analyzed within the coupled channels framework including appropriate symmetrization. The set obtained withr 0=1.01 fm,r I =0.86 fm for seven incident energies gave the best agreement with the data and could be, therefore, considered as really significant when compared with other sets. Coupled channels calculations have been made to fit the data and it has been found that they require a reduction of the imaginary potential. The total reaction cross-sectionσ R (E) determined from this analysis is in good agreement with a direct and recent measurement of σ R . Quadrupole deformation parameterβ 2 has been extracted and compared with those obtained for proton and alpha scatterings. Some small energy dependence of β2 over this energy range has been found, ¦β 2¦ ∼0.39–0.47. Finally, these calculations further confirm that β2 depends on the probe used in the various scattering experiments. For composite projectile such asα or12C,β 2 is clearly smaller than that one for nucleon as projectile.

Optical-model analysis of the elastic scattering of12C +12C in the energy range (11 ÷ 24) MeV/nucleon

Elastic scattering of12C +12C in the energy range (11 ÷ 24) MeV/nucleon has been analysed to derive optical-model parameters. The analysis using the Woods-Saxon potential and including symmetrization has shown that the following fixed couple of geometrical parameters (r0,rI) gave the best fit to the data. Four sets of optical-model parameters which gave good agreement with the data have been found by keeping (r0,rI) fixed, the best of them is the set obtained withr0 = 1.01 fm,rI = 0.86 fm for seven incident energies. The total reaction cross-section σR(E) determined from this optical-model analysis varies between approximately 1550 and 1380 mb, in agreement with those deduced from another analysis using the double-folding model and with a direct and recent measurement of σR.

Soft Repulsive Core Effects in (d + d) Scattering and Reaction

Using the single-channel resonating group method, in which a central nucleon-nucleon potential containing a soft repulsive core (SRC) is adopted, the (d + d) scattering phase shifts, differential scattering cross sections, and total reaction cross sections at a series of energies <20 MeV with and without imaginary potentials are calculated. The agreement between the theoretical and experimental results is quite good. The main conclusions are: The (d + d) nonlocal kernel function KS (R, R’) deduced is correct; hence, the discrepancy between the kernels in other similar work is clarified. The SRC causes a decrease in the total strength of the (d − d) direct potential VNs(R) and, in particular, the strength of VNs for short range and small channel spin s decreases much more. The SRC causes a decrease in the phase shifts δls(E) (toward the negative direction); the decrease is especially large when E is at or near a resonating energy. The SRC reduces the total reaction cross sections σR appreciably and causes a distinct increase in the differential scattering cross sections dσ/dΩ(θ) at the forward and backward angles; however, it does not greatly influence the differential cross sections at other angles.

The influence of the spectroscopic deformation of Li-isotopes on their interaction with51V

The energy dependence of the total reaction cross sectionσr and its tensor analyzing powerT20r was measured for the7Li−51V interaction in the energy rangeELi=10–20 MeV using two different experimental methods. Reaction residues were observed directly by their characteristicγ-emission, and the elastic scattering of7Li from51V was investigated. Additionally, the elastic scattering of6Li from51V was measured at 9.8, 12 and 14 MeV. The tensor analyzing power data can be interpreted as being caused by the spectroscopic mass deformation of the Li-ions. The energy dependence of σr andT20r above the Coulomb barrier can be described in terms of the classical sharp-cutoff model.

Monte Carlo calculations of reaction rates and energy distributions among reaction products, F+D2→DF+D

A three-dimensional classical trajectory analysis is used to determine the reaction dynamics of the reaction F + D2(v, J) → DF(v′, J′) + D on an assumed London-Eyring-Polanyi-Sato (LEPS) potential energy surface. Monte Carlo procedures are used to start each collision trajectory. An analysis is presented of the dependences of the total reaction cross sections σr and specific reaction cross sections σ(v, J, v′, ER ) on the relative translational energy and initial vibrational and rotational energy of the reagent molecule D2(v, J). Data are presented of the temperature dependences of (1) the vibrational, rotational and translational energy distributions of the reaction products and (2) the rate constants for formation of DF in specific vibrational and rotational states. The probability that direct reaction between atomic fluorine and molecular deuterium will lead to formation of DF in the v′ = 0 state was found to be zero. The ratio k(v′ = 4)/ k(v′ = 3) appears to be independent of temperature and has a value of 0·65, which is in excellent agreement with recent infra-red chemiluminescence experimental data. The ratio k(v′ = 2)/k(v′ = 3) has a slight temperature dependence and, at room temperature, has a value of 0·28. The ratio k(v′ = 1)/k(v′ = 3) was assumed independent of temperature and was assigned a value of 0·08. The results are compared with available experimental data and with previous theoretical studies.