Scattering of polarized protons by helium from 0.9 to 3.2 MeV

doi:10.1016/0375-9474(67)90237-0

Nuclear Physics A

Volume 90, Issue 2, January 1967, Pages 334-338

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Abstract

Polarized protons have been scattered from ⁴He. The left-right asymmetry has been observed at 110 points for energies from 0.94 to 3.2 MeV and for lab scattering angles from 30° to 140°.

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Cited by (9)

The polarized proton capture reaction 7Li(d, γ)8Be in the energy range from 380 to 960 keV
1977, Nuclear Physics, Section A
The polarized proton capture in ⁷Li was used to study the reaction mechanism and to obtain spectroscopic information on the ⁸Be nucleus. Gamma-ray angular distributions of the analyzing power were measured as a function of proton energy from E_p = 380–960 keV with three Ge(Li) detectors simultaneously. The excitation functions of the cross section and the analyzing power are strongly energy dependent. The data were analyzed unambiguously and represented by three R-matrix elements, two M1 and one E1. The energy dependence of the two M1 matrix elements agrees with the well-known two 1⁺ resonances at E_x = 17.642 and 18.157 MeV. The energy dependence of the E1 matrix element shows a smooth background presumably caused by a direct-capture mechanism, and furthermore, a resonant contribution, which is a significant suggestion of a new 1⁻ state in the ⁸Be system at E_x = 17.70 MeV with a width of Γ_p = 180 keV.
Étude des états P<inf> 3 2</inf> etP<inf> 1 2</inf> des noyaux 5He et 5Li par les diffusions n + 4He et p + 4He
1974, Nuclear Physics, Section A
Differential cross sections have been measured for ⁴He + p elastic scattering in the angular range from 30° to 165° and at incident energies ranging from 0.5 to 3 MeV. These data and previously existing cross section and polarization data are analyzed in the framework of the Humblet-Rosenfeld S-matrix theory. The characteristics of the $P_{32}$ and $P_{12}$ ⁵Li levels are deduce A similar analysis is performed for the ⁴He + n elastic scattering and the spectroscopic characteristics of the mirror nucleus ⁵He P-levels are then deduced. These results seem to be less ambiguous than those of phase shift R-matrix analyses and are in good agreement with nuclear reactions results. The spin-orbit splitting is found to be of the order of 2.1 MeV for the two nuclei. Mass excesses of ⁵He and ⁵Li are found to be 11.275 ± 0.05 MeV and 11.313 ± 0.1 MeV respectively.
7Li(p, n)7Be reaction with polarized protons from the threshold to 3.0 MeV
1973, Nuclear Physics, Section A
A polarized beam was used to measure angular distributions of the proton analyzing power of the ⁷Li(p,n)⁷Be reaction at 11 energies from 2.05 to 3.00 MeV. The analyzing power is generally large and positive. The analyzing power can be fitted with associated Legendre polynomials. The coefficient of P₁¹ rises rapidly from threshold to a maximum near the 3⁺ state at 2.25 MeV from which it drops to a minimum at 2.42 MeV, whence it gently rises to 3.00 MeV; the coefficient of P₂¹ has small values that increase with energy. The data were measured typically to an accuracy of 0.02 with a target 20 keV thick at 2 MeV bombarding energy. Polarization contour maps are given. Comparison of these analyzing power measurements with previous data for the neutron polarization induced with unpolarized protons shows equality at some energies and slightly higher values at others.
R-matrix formulation and phase shifts for n-4He and p-4He scattering for energies up to 20 MeV
1972, Nuclear Physics, Section A
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.
Absolute calibration of spin - 1 2 polarization
1971, Physics Letters B
Polarization measurements and phase shifts for p-4He scattering between 3 and 18 MeV
1971, Nuclear Physics, Section A
Angular distributions of the polarization in proton elastic scattering from ⁴He were measured at laboratory energies near 4.6, 6.0, 7.9, 9.9 and 11.9 MeV. A phase-shift analysis of available cross-section and polarization angular distributions between 3.0 and 17.5 MeV was performed. The energy dependence of the phase shifts was represented by an effective-range expansion. The phase shifts determined from this expansion permit calculation of the p-⁴He polarization with an accuracy of better than ± 0.02 in this energy range.

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^†: Fellow of the Swiss National Foundation and the Carnegie Institution.

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Nuclear Physics A

Abstract

References (10)

J. Phys. Rev.

Phys. Rev.

Phil. Mag.

Phys. Rev.

Phys. Rev.

Phys. Rev.

Nuclear Physics

Cited by (9)

The polarized proton capture reaction <sup>7</sup>Li(d, γ)<sup>8</sup>Be in the energy range from 380 to 960 keV

Étude des états P<inf> 3 2</inf> etP<inf> 1 2</inf> des noyaux <sup>5</sup>He et <sup>5</sup>Li par les diffusions n + <sup>4</sup>He et p + <sup>4</sup>He

<sup>7</sup>Li(p, n)<sup>7</sup>Be reaction with polarized protons from the threshold to 3.0 MeV

R-matrix formulation and phase shifts for n-<sup>4</sup>He and p-<sup>4</sup>He scattering for energies up to 20 MeV

Absolute calibration of spin - 1 2 polarization

Polarization measurements and phase shifts for p-<sup>4</sup>He scattering between 3 and 18 MeV