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.     

The polarization of 3He elastically scattered from 27Al and 28Si at 21 MeV

The polarization of 21 MeV ³He elastically scattered from ²⁷Al and ²⁸Si has been measured in an angular range of θ_lab = 25°–55°. Differential cross-section data have been obtained out to angles of approximately 100°. The small values observed in the polarization distributions differ somewhat from optical-model predictions based on fits to the differential cross-section data and cannot be used to obtain significant information about the optical-model spin-orbit potential. It is concluded that statistically significant, non-zero ³He polarization measurements will not be possible using traditional double scattering techniques for ³He energies ≦ 27 MeV and targets of $\text{Z ≧ 13}$.     

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.     

Proton-hole states in 57Co studied with the 58Ni(d, 3He) 57Co reaction at 78 MeV

The ⁵⁸Ni(d, ³He)⁵⁷Co reaction was measured at a bombarding energy of 78 MeV. Energy levels up to 7.0 MeV excitation energy in ⁵⁷Co were studied. Angular distributions of the ³He particles, corresponding to transitions to the ground state and to 42 excited states in ⁵⁷Co, were analyzed in the range of θ_lab = 2.7° to 25°. Exact finite-range DWBA calculations were employed to extract l-values and spectroscopic factors. Shell-model calculations were carried out in an fp-shell model space. In addition, calculations of the energy levels in ⁵⁷Co were performed in the SU(6) particle-vibration model (PTQM). Satisfactory agreement is observed between the experimental results and both theoretical predictions.     

A study of the 90Zr(6Li, 6He)90Nb reaction at E6Li = 93 MeV

The energy spectra of ⁶He nuclei from the ⁹⁰Zr(⁶Li, ⁶He) reaction at E_{⁶Li = 93 MeV} have been measured over the angular range of 7 ° ? θ_lab ? 20 °. The theoretical DWBA analysis of these spectra and angular distributions was performed employing transition densities of bound and resonance states obtained on the basis of the theory of finite Fermi systems. It is shown that up to excitation energies of E_x ≈ 10 MeV in ⁹⁰Nb a direct charge-exchange mechanism dominates in this reaction, while at higher E_x the contribution made by multistep processes increases significantly. It is also shown that the quasi-elastic cross section is determined by a sum of partial contributions of spin-isospin-flip transitions with multipolarities L=0 through L=6.     

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.     

Spectroscopy of intermediate 16F states with the reaction 14N(3He,np)15O

Excited states of ¹⁶F have been investigated with the reaction ¹⁴N(³He, np)¹⁵O at E = 10.5 and 12 MeV in kinematically complete experiments. Proton groups corresponding to the decays of intermediate ¹⁶F states were observed at various angles with counter telescopes in time coincidence with the associated neutrons detected at θ_n^lab = 0° with a time-of-flight spectrometer. Excitation energies and decay widths Γ_p0 of these states have been extracted from the proton spectra. Lower limits for the orbital angular momentum in the decay channel and for the spin of the states have been deduced from the obtained angular correlations. By comparison with the reaction ¹⁴N(³He, pp)¹⁵N measured at E = 13 MeV, pairs of $\text{T = 1}{}^{16}\text{F}$ parent/¹⁶O analog states have been identified. J^π assignments and shell-model configurations are discussed on the basis of the selectivity of the reactions measured.     

3He D-state effects in (d, 3He) reactions

The tensor analysing power of the ²⁷Al(d, ³He)²⁶Mg reaction has been measured at E_d = 12.4 MeV. The results are reproduced by predictions of the DWBA including D-state components in the ³He wave function. The magnitude of the tensor analysing power provides information on the asymptotic D-state to S-state ratio in the ³He wave function. The value obtained for ³He is in agreement with the corresponding value for ³H.     

Analysis of 1 GeV proton scattering on D and 4He in a non-eikonal approach

A recently formulated theory for multiple hadron scattering is applied to 1.7 GeV/c scattering on D and ⁴He .Agreement is obtained for pD up to θ_CM ～ 90° and for p⁴He over the entire range measured (θ_CM ? 65°).     

Pulsed NMR frequency shifts in superfluid 3He

We report the first measurements of the NMR frequency in ³He A and B under conditions where the net magnetization, M, is tipped far from its equilibrium direction along H_O. In ³He A the frequency shift ω - γH_O varies from the continuous wave value at tipping angle Φ = 0 to a negative shift at Φ = 180°. In ³He B no frequency shift is observed, however for Φ ? 100° a beat pattern is seen to develop in the free induction decay envelope.     

The 4He(p,d)3He reaction at 770 MeV

The differential cross section of the ⁴He(p, d)³He pick-up reaction has been measured at E_p = 770 MeV. The data are analysed in the framework of the DWBA; both one-nucleon and one-N¹ transfers are considered.     

Giant-resonance excitation by 130 MeV 3He

Energy spectra of 130 MeV ³He scattered from ²⁴Mg, ⁹⁰Zr, ¹²⁰Sn and ²⁰⁸Pb have been measured. The spectra exhibit a pronounced giant resonance (GR) structure in the excitation energy region around $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{≈ 63A}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}\text{MeV}$. The GR angular distributions as well as those corresponding to the first 2⁺ levels in ²⁴Mg and ¹²⁰Sn have been obtained for angles 7° ≦ θ_L ≦ 35°. Distorted wave calculations using the optical model parameters fitting the elastic data resulted in good fits to the 2⁺ levels. For ²⁴Mg, ⁹⁰Zr and ¹²⁰Sn the shapes of the GR angular distributions are well fitted by L = 2 curves alone. However, for ²⁰⁸Pb both L = 2 and L = 4 curves give fits of comparable quality.     

Alpha-heavy-ion angular correlations from 28Si + 12C

Alpha particles have been measured in coincidence with heavy recoil nuclei from the ²⁸Si + ¹²C reaction. At E_lab = 87 MeV angular correlations for alphas between 15° and 55° and heavy ions at angles ?9°, ?12° and ?15° have been taken. An excitation function of coincidence events with θ_α = 30° and θ_HI = ?12° has been measured for 84 MeV < E_lab < 91.5 MeV. The results are well described by a statistical-model calculation for compound nucleus decay. No evidence is found for additional processes.     

Elastic π± + 3He scattering

Differential cross sections have been measured at θ≈20–120° at 50, 100 and 200 MeV. Salient features of the angular distributions are Coulomb interference effects at 50 MeV and clear spin-flip contributions to π^? compared to π⁺ scattering in the angular region of θ≈80° dominated by the πN p-wave minimum. Comparison with optical model calculations account for the data up to 200 MeV while this first-order scattering theory misses conspicuous features of data at 295 MeV.     

A study of the 2H(d,p)3H AND 2H(d,n)3He reactions and the excited state of 4He at 23.9 MeV

The relative differential cross sections have been measured for the ²H(d, p)³H and the ²H(d, n)³He reactions from 300 keV to 700 keV in 50 keV steps. Angular distributions of all charged particles from the reactions were taken from 20° to 160° in the laboratory system. Energy-dependent asymmetry coefficients from the expansion of the centre-of-mass angular distributions in terms of even powers of cos θ were obtained as were the branching ratios between the two reaction modes. The different energy dependences of the moments of the two cross sections were used to test the need for the existence of a recently reported T = 0 state in ⁴He.     

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.     

Two-body photodisintegration of 3He and 4He in the Δ(1236) region

Differential cross sections for the reactions ³He(γ, p)d and ⁴He(γ, p)t were measured at proton c.m. angles of 60° and 90° for photon energies ranging from 150–450 MeV with an average resolution of 8 MeV. Bremsstrahlung was used as the photon source; deuterons/tritons were analyzed in a magnetic spectrometer whereas coincident protons were detected in a plastic scintillator telescope. The experimental method includes a calibration by means of ¹H(γ, π⁰)p differential cross section measurement at 90° c.m. in the same photon energy range. The ³He and ⁴He two-body photodisintegration differential cross sections show a monotonically decreasing variation with photon energy. In addition, partial data on the differential cross section of the reaction ⁴He(γ, n)τ at 90° and 120° neutron c.m. angle are given.     

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°.     

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.     

Study of 74As by the 73Ge(3He,d) reaction

The energy levels of ⁷⁴As have been studied using the ⁷³Ge(³He, d)⁷⁴As reaction at an incident energy of 17 MeV. The overall energy resolution was 30 keV. Twenty-five levels in ⁷⁴As were identified up to 2.2 MeV excitation energy and angular distributions were measured in the interval $\text{3}\text{3}\text{4}\text{°}$ to $\text{86}\text{1}\text{4}\text{°}$. Spectroscopic strengths and l_p values have been extracted for many of the transitions by means of a distorted-wave analysis of the differential cross sections. A comparison with the ⁷⁵As(p, d) data suggests the presence of several unresolved doublets in ⁷⁴As.