Intermediate-energy proton-4He elastic scattering with a microscopic optical potential

A microscopic, momentum space, optical potential calculation of elastic p-⁴He scattering is compared with 100–200 MeV data over the full angular range. The least sophisticated potential explains the occurrence and energy dependence of the back angle peak.     

R-matrix formulation and phase shifts for n-He and p-He scattering for energies up to 20 MeV

An R-matrix formulation for a single level with a background approximation has been used to analyse n-⁴He and p-⁴He elastic scattering data below the inelastic thresholds near 22 MeV. For every partial wave a single level and a distant pole contribution constant with energy has been employed. Simple relations between neutron and proton scattering parameters have been sought to possibly derive more dependable values for neutron phase shifts and analysing powers at energies where little experimental information exists. The R-matrix parameters corresponding to ⁵He and ⁵Li ground and 1st excited states, phase shifts up to 20 MeV and neutron analysing powers up to 15 MeV are given in tabular form and are compared to results of earlier analyses. Differences in n-⁴He phase shifts are discussed and shown to be due to a scarcity of accurate neutron scattering data above 11 MeV. Some typical fits to n-⁴He scattering data are shown.     

Analyzing power of n-3He elastic scattering from 1 to 2 MeV

Measurements of the analyzing power A_y of the elastic n-³He scattering in the energy range from 0.95 to 2.0 MeV are reported. These results improve considerably the precision of the data base in the low energy domain. Recent R-matrix predictions are used as starting parameters in phase-shift analyses. The comparison with p-³H and p-³He data at nearby energies reveals the importance of Coulomb effects at these low energies and of the isospin structure of the A = 4 system.     

Inelastic p-He scattering at 141 MeV

Inelastic p-⁴He scattering at 141±2 MeV has been investigated with a high-pressure cloud chamber filled with helium. Results are presented for the total cross sections of each reaction channel and the neutron spectra for the p(⁴He, pn)³He reaction.     

Quest for the 10He nucleus

The spectrum of ¹⁰He was studied by means of the ³H(⁸He, p)¹⁰He reaction at a laboratory energy of 25 MeV/A and small center-of-mass angles. Missing mass spectrum of ¹⁰He was derived from the obtained p-⁸He coincidence. A resolution of 0.7 MeV was achieved in this spectrum for the measured ¹⁰He energy. Most likely, a well isolated group of 10 events detected between 2 and 5 MeV and showing a maximum at about 3 MeV in the spectrum of the present work exhibits the ¹⁰He g.s. resonance.     

Elastic proton-3He scattering at large angles and intermediate energies

Large-angle p-³He elastic scattering differential cross section have been measured at E_p = 415 and 600 MeV where they look very similar, and at 800 MeV where the cross section is 10% of the value at 600 MeV. A one-meson-plus-2N exchange mechanism could explain this feature.     

(p, 4He) Elastic scattering at 350, 650, 1050 and 1150 MeV

Angular distributions of p-⁴He elastic scattering differential cross sections have been measured at 350, 650, 1050 and 1150 MeV, in regions of four-momentum transfer squared t = 0.02–0.71 (GeV/c)². These new measurements confirm the absence of a pronounced first diffraction minimum. New theoretical analyses are also presented.     

An Investigation of Relativistic Microscopic Optical Potential in Terms of Relativistic Brueckner-Bethe-Goldstone Equation

Relativistic microscopic optical potential of nucleon-nucleus is derived from the relativistic Brueckner-Bethe-Goldstone (RBBG) equation.The complex effective mass of a nucleon is determined by a fit to 200MeV p-⁴⁰Ca scattering data.The relativistic microscopic optical potentials with this effective mass are obtained from RBBG for p-¹⁶O,⁴⁰Ca,⁹⁰Zr and ²⁰⁸Pb scattering in energy range from 160 to 180MeV.The microscopic optical potential is used to study the proton-⁴⁰Ca scattering problem at 200MeV.The results,such as defferential cross section,analyzing power and spin rotation function are compared with those calculated from phenomenological relativistic optical potential.     

动量空间中能质子-12C弹性散射截面和自旋量的研究

在KMT理论框架下，应用微观的动量空间一级光学势，包括了库仑修正，自旋关联，NN振幅反对称，离壳效应，核子反冲和结合能转换，Lorentz不变的角变换.在整个中能区域系统地计算了质子-¹²C弹性散射微分截面和自旋观测量，并与实验数据及Glauber理论框架下或已有的其他理论计算结果做了比较，其结果显示，在200—1000MeV，该理论与实验结论符合程度较好.     

Analyzing power measurements for p-3He elastic scattering from 1.75 to 4.50 MeV

Analyzing powers for p-³He elastic scattering have been measured at 12 energies between 1.75 and 4.50 MeV for θ_c.m. = 40° to 150°. A comparison of our results with earlier data of Drigo et al. shows substantial differences at all energies. The R-matrix fits to our data that were included in the global search calculations of Hale and Dodder are shown. These calculations established the ordering of the lowest-lying T = 1 levels of ⁴He as J^π = 2^?, 1^? (triplet), 0^?, and 1^? (singlet), which is the WMI (MHI) ordering.     

Optical reaction cross-sections for light projectiles

The optical reaction cross-sections forn, p,²H,³He,³He and⁴He for several global optical potentials available in the literature have been parametrized in terms of simple empirical expressions which are smooth functions of the target mass number and the projectile energy. The empirical forms are 5–10% accurate over the periodic table and energy-range upto 50 MeV. They can be conveniently used in calculations where the optical reaction cross-sections are required as input. The calculation of proton spectra in the (n, p) reaction at 14 MeV is discussed.     

The elastic scattering of 3He on 4He at medium energies

The differential cross section of the elastic scattering ³He(⁴He, ⁴He)³He has been measured at center of mass energies E_c.m. between 28 and 44 MeV and in the c.m. angular range of 20° to 160°. The ³He polarization P at E_c.m. = 42 MeV and θ_c.m. = 132° was determined in a double scattering experiment. The analysis of the cross section data with the optical and the cluster model has been described previously. The phase shifts obtained in the cluster model calculations were used as starting values in a phase shift analysis. The resulting final real phase shifts and elasticity parameters give good fits to the cross section data. At 44 MeV the elasticity parameters show a pronounced odd-even dependence on angular momentum which had been found already in the case of the real phase shifts. The result of the polarization experiment |P| < 0.22 is consistent with cluster model predictions.     

6Li elastic scattering ON 12C, 16O, 40Ca, 58Ni, 74Ge, 124Sn, 166Er and 208Pb at E(6Li) = 50.6 MeV

The elastic scattering of ⁶Li ions from a variety of targets, A = 12 to 208, has been measured at a bombarding energy of 50.6 MeV. The angular distributions are characteristic of strongly absorbed particles, such as ³He and heavy ions, and less diffractive than for ⁴He. A simple optical model with Woods-Saxon real and imaginary volume potentials is adequate to fit the data. Spin-orbit effects are not apparent in the data.     

Proton-3He elastic scattering: A phase-shift analysis by a separable potential model

All the available experimental data (cross sections, projectile and target polarizations, polarization transfer coefficients) on p-³He elastic scattering up to ~10 MeV are analyzed on a unified basis in the framework of a separable potential model. This allows a phase-shift analysis which is model dependent, but is averaged over a wide energy interval (757 experimental points are reproduced by 27 model parameters). The calculations confirm some indications, already present in the literature, of a weak S-D tensor mixing, and strong singlet-triplet mixing in the P-states. Our conclusions are that probably the leading non-central effect is given by the coupling s₁ · l between the incident proton spin s₁ and the orbital angular momentum of relative motion. Finally, the phase shifts and observables are recalculated using the p-³He potential parameters, but switching off the Coulomb interaction. The results are compared with the (few) n-³H experimental cross sections of the literature, and the agreement is good, as expected on the basis of the charge-symmetry law.     

Energy dependence of the optical model parameters for 3He ions scattered from 40Ca and 58Ni

The differential cross sections for the elastic scattering of ³He ions on targets of ⁴⁰Ca and ⁵⁸Ni have been measured at incident energies of 27.7, 51.4, 73.2 and 83.5 MeV. The results of optical model analyses showed that only one unique potential (J_R ≈ 330 MeV · fm³) with a surface absorptive term can provide acceptable fits to the large angle elastic scattering cross sections at 83.5 MeV. The particular geometrical set found at 83.5 MeV could not, however, give an adequate fit to the data with energy less than 40 MeV. Subsequent analyses indicated that a break in the energy dependence of the real potential is observed for the low energy data. Explicit energy dependent terms were obtained by fitting all the data simultaneously. These phenomenological potentials were also compared with the folded nucleon-nucleus potential. The influence of the α-particle channels on the elastic scattering of ³He ions at 83.5 MeV was also examined.     

Elastic 3He scattering from even Ar isotopes and backward-angle anomalies in the systematics of elastic 3He scattering

Angular distributions have been measured for ³He elastic scattering from ^{36, 38, 40}Ar at 26.5 MeV and from ³⁶Ar and ⁴⁰Ca at energies between 24.5 and 28 MeV. This scattering clearly shows features of “anomalous” backward-angle scattering, which is discussed in the systematics of ³He scattering from heavier target nuclei. The data for “anomalous” scattering can be described by optical potentials which show features significantly different from those of “normal” scattering. These features are smaller radius parameters for the real optical potential and a strongly reduced volume integral for the imaginary potential.     

Experimental Study of Photon Induced Reactions on 3He and 4He at Low Energies

Data are reported for the photodisintegration cross section of the reaction ³He(??, p)²H at ten energies between 7.0 and 16.0?MeV. Very preliminary data are presented for the reaction ⁴He(??, p)³H between 22.0 and 29.5?MeV in 0.5?MeV energy steps, and for the reaction ⁴He(??, n)³He at three energies around 28.0?MeV. High-pressure He/Xe gas scintillators served as target and detector. Our data are in better agreement with recent theoretical calculations than the majority of the existing data for all three reactions, but differ significantly from recent data taken with a mono-energetic photon beam and a time-projection chamber.     

Inelastic processes in the 19F(3He,d)20Ne reaction

We have examined the role of inelastic processes in the ¹⁹F(³He, d)²⁰Ne reaction. By coupling three levels in both the entrance and exit channels it was found that the inelastic processes were able to account for both the magnitude and rather flat shape of the angular distribution for the 4.25 MeV 4⁺ level observed in the ¹⁹F(³He, d)²⁰Ne reaction at 16 MeV bombarding energy. In contrast the DWBA could not account for the data. The magnitude of the inelastic processes was found to be quite sensitive to some of the optical model parameters involved. The DWBA predictions for the 0⁺ and 2⁺ cross sections were modified by the inelastic processes requiring some adjustment of the spectroscopic amplitudes to account for the data.     

Diagnostics of the region of nuclear interactions of neutrons in the solar flare of January 20, 2005 by gamma-ray lines

Based on an analysis of the time history of the count rate in the 2.223 MeV neutron-capture line from the extreme solar event of January 20, 2005, we investigate the density of the surrounding medium and the 3He content in the area of the 2.223 MeV gamma-line production. The analysis uses data on count rates in the 2.223 MeV gamma-ray line, as well as in lines ranging from 4 to 7 MeV, which were acquired with the AVS-F apparatus from the SONG-D detector onboard the CORONAS-F satellite. It is shown that simulation of the time history of the 2.223 MeV gamma-ray line from the flare event would require an assumption of the elevated abundance of 3He. It is found that in the area of the 2.223 MeV gamma-line production the ratio n(³He)/n(¹H) is (1.4 ± 0.15) × 10^?4, although, based on the data from different flares, on average it is approximately 2 × 10^?5. The elevated abundance of ³He may be considered as an additional indirect argument for the possible presence of reaction products of neutron radiative absorption by the 3He isotope within a small increase in gamma emission in the 15?C21 MeV range over the background level (which was detected previously from the CORONAS-F/AVS-F data).