Measurement of the proton polarization in the 3He(d,p)4He Rection between 2.0 and 6.0 MeV

Angular distributions of the polarization of ³He(d, p)⁴He protons have been measured for unpolarized deuterons with laboratory energies of 1.99, 2.81, 3.94 and 6.00 MeV. The polarizations were determined from the left-right asymmetry of elastic scattering through 60° in ⁴He gas using a vaned polarimeter whose analyzing power was computed by trajectory tracing from the known p-α polarizations. A contour diagram of proton polarization for deuteron energies of 1 to 12 MeV is presented. A Legendre polynomial expansion of four or five terms has been fitted to the products p(θ)σ(θ). The coefficients of the expansions of these and other measurements show resonance-like behaviour at ⁵Li excitations of 20.0 and 20.9 MeV. The vector-polarized beam and polarized-target analyzing powers are compared with the proton polarization. The proton polarizations are in good agreement with the ³H(d, n)⁴He neutron polarizations when compared at the same entrance-channel energy but disagree when compared at equal exit-channel energies or compound-nucleus excitations.     

Quasifree processes in the 2H + 3He interaction

Quasifree scattering and quasifree reaction processes have been examined in the ³He+ ²H → p+d+d, ³He + ²H → n+p+³He and ³He+²H → p+p+t reactions. Beam energies of E_d = 22.3 and 35 MeV and of E_3He = 30, 33.5, and 52.5 MeV were used. The experimental results are compared with PWIA calculations and Fourier transforms of the wave functions are extracted. The quasifree processes are described qualitatively by the PWIA, but some features cannot be described by either PWIA or DWIA.     

Liquid 3He droplets: Energy systematics and magic numbers

Ground state properties of ³He clusters are investigated in the framework of the Hartree-Fock theory using an effective interaction of phenomenological type. Binding energies and density distributions are evaluated for clusters up to N = 168 atoms. The analysis yields magic number effects at N = 40 and 70. The method predicts the existence of a minimum number of particles forming a bound droplet around N = 20.     

A study of the 2H(3He, 4He)1H reaction with a polarised 3He beam at 27 and 33 MeV

Angular distributions of the ³He analysing power and differential cross section were measured for the ²H(³He, ⁴He)¹H reaction at incident ³He lab energies of 27 and 33 MeV. Analysis of this and other data suggest the presence of a broad resonance, or resonances, around 28 MeV excitation in ⁵Li. The evidence for the dominant M-matrix elements involving a change in channel spin (i.e. the ΔS = ?1 rule) is examined and also the question is investigated as to whether the data can be consistently explained without requiring tensor forces in the interaction.     

The tensor analyzing power AzzATθ = 0° for the 3He(d, p)4He reaction

The tensor analyzing power f_zz has been measured for the ³He($\text{d}$, p)⁴He reaction at 0 = 0° over an incident deuteron energy range E_d = 6.6–15.8 MeV in steps of 0.5 MeV. The present results agree with and extend the previous measurements of Grüebler et al. The present results indicate that this reaction is a very good tensor analyzer for polarized deuteron beams with energies up to 15.8 MeV.     

The elastic scattering of polarized 3He by 3He and excitation in the 6Be system

Angular distributions of the polarization in the elastic scattering of ³He by ³He have been measured at eight energies between 18 and 33 MeV, corresponding to excitation of ⁶Be between 20.5 and 28 MeV. The measurements were made using the 33 MeV polarised ³He beam at the University of Birmingham Radial Ridge cyclotron and a small gas target. The data have been analysed in terms of real and complex phase shifts. The deduced phase shift energy dependence cannot be associated with a single isolated level in ⁶Be, however an application of the two-level R-matrix formula reveals some broad L = 3 structures around E_x = 25 MeV.     

Inclusive π4He scattering and the πN interaction in the nuclear medium

Double differential cross sections for the inclusive reaction ⁴He(π, π′)X have been measured for six pion energies between 90 and 320 MeV and an angular range from 30° to 135°. The data are interpreted in terms of the Δ-hole formalism. Medium corrections to the free π-nucleon scattering operator are important for a quantitative understanding of our results. Total inelastic cross sections are obtained and estimates for the absorption cross section are given.     

The inclusion of the Fermi motion in elastic pion-nucleus scattering calculations

Taking into account the motion of target nucleons, additional terms in the Kisslinger optical-model potential are obtained. The proposed method is applicable at energies sufficiently below the ($\text{3}\text{2}\text{,}\text{3}\text{2}$) resonance. At such energies, good fits to the available data have been found for the reactions π-¹²C and π-¹⁶O and an improvement occurs also for the π-⁴He reaction. Our model gives surprisingly good results for π-⁴He reactions in the vicinity of the resonance at 110 and 150 MeV.     

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.     

Investigation of the 6Li(d, α)4He reaction between 1.5 and 11.5 MeV

The differential cross section σ₀(θ) and the analysing powers T₁₁(θ), T₂₀(θ), T₂₁(θ) and T₂₂(θ) of the reaction ⁶Li(d, α)⁴He have been measured for twelve energies between 1.5 and 11.5 MeV at c.m. angles between 3.5° and 90°. The results were fitted with Legendre polynomials. The energy dependence of the resulting coefficients indicates resonance-like behaviour at several energies corresponding to excitation between 22 and 32 MeV in ⁸Be. The reaction ⁶Li(d, α)⁴He shows excellent features as an analyser for deuteron vector and tensor polarization over the whole energy range investigated.     

Low-lying states of the 16F nucleus

Low-lying proton-emitting states of ¹⁶F have been investigated through the sequential particle decay reactions ¹⁴N(³He, n)¹⁶F(p)¹⁵O. Excitation energies were determined by measuring outgoing proton energies. Estimations of proton decay widths and spin limitations were made from proton spectra and angular correlation data which were obtained by detecting the protons in time coincidence with the associated neutrons at θ_n = 0°. To date, the ground-state spin of ¹⁶F has been considered to be J = 0; however, the present work suggests J = 1 to be preferable.     

The reaction 14C(3He,n)16O and the coexistence model of 16O

The reaction ¹⁴C(³He, n)¹⁶O has been measured at a ³He bombarding energy of 25.4 MeV. The zero-degree differential cross section for the excitation of the three low lying 0⁺T = 0 states, at energies 0.0, 6.05 and 12.05 MeV are, respectively, 1.33 ± 0.10, 0.49 ± 0.10, and 0.50 ± 0.10 mb/sr These measured cross sections are in rough agreement with single-step zero-range DWBA calculations using an empirically determined ¹⁴C ground state wave function and in which the Brown and Green coexistence-model wave functions are used to describe the ¹⁶O 0⁺ states. The angular distribution of the transition to the ground state is measured between 0° and 32°.     

Search for Ay = 1 and Ayy = 1 points in the 6Li(d, α)4He reaction

A search for vector analysing power A_y = 1 and tensor analysing power A_yy = 1 values of the ⁶Li(d, α)⁴He reaction in the energy region between 5.0 and 6.5 MeV as well as between 8.0 and 10.0 MeV was performed experimentally. Two A_yy maxima which are compatible with unity were found. No A_y = 1 point could be detected. The precise energies and angles for the maxima were determined by interpolation of the experimental data.     

Three-body continuum structure and response functions of halo nuclei (I): 6He

Three-body scattering states of the Borromean two-neutron halo nuclei are explored in a core + n + n model using the method of hyperspherical harmonics. We analyse the continuum structure (the properties of the continuum wave functions) separately from the continuum response (the magnitudes of one-step transitions from the ground state to the continuum). Predictions are made for the positions and strengths of the isoscalar monopole, electric dipole and quadrupole excitations, as well as for nuclear inelastic and charge-exchange response functions, for the ⁶He nucleus. The known 2⁺ resonance in ⁶He is reproduced. We find 1⁻ strength concentrations at lower energies in the proximity of the three-body threshold, and predict new 2⁺, 1⁺ (and possibly 0⁺) resonances at slightly higher energies in ⁶He.     

Energy and angular distributions in 6He photodisintegration

Energy and angular distributions of the neutrons and the α particle from the reaction ⁶He(γ, 2n)⁴He is examined in the minimal approximation of the hyperspherical-function method in the algebraic version of the resonating-group method. The differential cross section for ⁶He photodisintegration is calculated as a function of the energies of the product particles, the angles between their momenta, and their emission angles with respect to the incident-photon momentum.     

Low-energy behavior of the 3He(α, γ)7Be cross section

Cross sections for the ³He(α, γ)⁷Be reaction have been measured at several energies from E_c.m. = 165 to 1169 keV by counting prompt γ-rays from a windowless, differentially pumped, recirculating, ³He gas target. The cross-section factor S₃₄(E_c.m.) and branching ratio γ₁/γ₀ were determined at each energy. Cross sections were also measured at E_c.m. = 947 and 1255 keV by counting the γ-rays from the ⁷Be produced in a ³He gas cell with a Ni entrance foil. Combining the results of these two independent experiments yields a zero-energy intercept for the cross-section factor of S₃₄(0) = 0.53 ± 0.03 keV · b. The relationship between these measurements and several theoretical calculations, and the import of the extrapolated cross section for the solar-neutrino problem are discussed.     

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.     

Astrophysical S factors of radiative 3He4He, 3H4He, and 2H4He capture

The possibility of describing the astrophysical S factors for radiative ³He⁴He capture at energies of up to 15 keV and radiative ³H⁴He and ²H⁴He capture at energies of up 5 keV is considered on the basis of the potential cluster model involving forbidden states.     

Experimental investigation of highly excited states of the 5,6He and 5,6Li nuclei in the (6Li, 7Be) and (6Li, 7Li) one-nucleon pickup reactions

The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions on ⁶Li and ⁷Li nuclei were investigated in the angular interval 0°–20° in the laboratory system at a ⁶Li energy of 93 MeV. In addition to low-lying states of the ^5,6He and ^5,6Li nuclei, broad structures were observed near the t(³He)+d and t(³He)+t thresholds at the excitation energies of 16.75 (3/2⁺) and ～20 MeV (for ⁵He), 16.66 (3/2⁺) and ～20 MeV (⁵Li), 14.0 and 25 MeV (⁶He), and ～20 MeV (⁶Li). The angular distributions measured in the ⁷Li(⁶Li, ⁷Be)⁶He reaction for transitions to the ground state (0⁺) and excited states at E _x=1.8 MeV (2⁺) and 14.0 MeV of the ⁶He nucleus were analyzed by the finite-range distorted-wave method assuming the 1p-and 1s-proton pickup mechanism. The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions were shown to proceed predominantly through the one-step pickup mechanism, and the broad structures observed at high excitation energies are considered as quasimolecular states of the t(³He)+d and t(³He)+t types.     

He同位素与H2分子碰撞第二振动激发分波截面的理论研究

用公认精确度较高的密耦近似方法计算了不同能量下惰性气体原子³He（⁴He,⁵He）与H₂分子替代碰撞体系的00-20,00-22,00-24,00-26第二振动激发分波截面.通过分析³He（⁴He,⁵He）-H₂碰撞体系第二振动激发分波截面的差异,总结出³He（⁴He,^{5关键词： 振动激发 分波截面 密耦方法 同位素}