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

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.     

The 15N(p, α)12C reaction with polarized protons from 0.34 to 1.21 MeV

A polarized beam was used to measure angular distributions of the analyzing power of the ¹⁵N(p, α)C reaction at 0.34 MeV and at five energies from 0.92 to 1.21 MeV. The analyzing power can be fitted with associated Legendre polynomials, P₁¹ and P¹₂ sufficing to describe the results except near 1.2 MeV where P₃¹ is also required. Polarization excitation functions were measured throughout the entire energy range at angles where the polynomials P¹₂ and P¹₃ are zero. A polarization contour map is given.     

Initial-state distortion and final-state interactions in the 2H(3He, 3He p)n and 2H(3He, 3H p)p reactions

The predictions of two fully antisymmetrized reaction theories (DWBA and PWBA-FSI) are compared with absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He, ³H p)p reactions exhibiting final-state interactions (FSI) and quasi-elastic scattering (QES) both with and without charge exchange. The DWBA theory takes into account both the initial ³He-d and the final N-N interactions, while the PWBA-FSI theory includes only the latter. New QES data at E_He = 35.9 MeV, as well as previously reported 26.8 and 35.9 MeV data, are fitted. The DWBA theory gives good fits, both in shape and magnitude, to spectra showing N-N final-state interactions but gives somewhat poorer fits to QES spectra whose predicted magnitudes are two to ten times too large. The PWBA-FSI theory always predicts cross sections that are too large; however the predicted shapes are about as good as those from the DWBA. The initial-state interaction is shown to affect both the width and position of QES peaks from these reactions.     

New highly excited 4He levels found by the 2H(d,p)3H reaction

The differential cross section, the vector- and the tensor-analyzing powers of the reaction ²H($\text{d}$, p)³H have been measured. The polarization data were obtained at 11 energies between 1.0 and 13 MeV at lab angles between 5° and 160°. The data were fitted with Legendre polynomials and the resulting coefficients analyzed for resonances in ⁴He. Overwhelming evidence for a 1^? level at 24.1 MeV and a strong indication of a 4⁺ level at 24.6 MeV excitation energy have been found.     

Effects of exchange and final-state interactions in the reactions 2H(3He, 3H p)p and 2H(3He, 3He p)n

Absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He,³H p)p reactions were measured at E_He = 35.9 MeV. Spectra dominated by the nucleon-nucleon final-state interaction (FSI) are fitted by a fully antisymmetrized PWBA theory which includes the effects of FSI in all its matrix elements. Previously reported 26.8 MeV data showing both FSI and quasi-elastic scattering (both with and without charge exchange) are also fitted by the theory, which qualitatively describes the shapes of all these spectra and the ratios of the cross sections for the various processes. Predictions of Watson-Migdal theory are fitted to the FSI spectra and differences between the two theories are analyzed.     

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.     

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.     

Neutron-neutron effective range from quasifree scattering 2H(n,nn)p at 25 MeV

A neutron coincidence spectrum from the deuteron breakup ²H(n, nn)p was measured at the kinematical condition of quasifree neutron-neutron scattering with 25 MeV neutrons in the entrance channel. The efficiencies of both scintillation detectors were calibrated in the same experimental arrangement as the breakup measurement was performed. The neutron flux was monitored by a proton recoil telescope. Absorption, double scattering and geometric conditions have been simulated by the Monte Carlo technique. From a fit based on the Ebenhöh-Bruinsma-Stuivenberg code with the neutron-neutron scattering length a_nn = ?16.6 fm for the effective range, the value r_{nn = 2.69 ± 0.27 fm} was determined.     

La réaction 2H(α, αp)n à 165 MeV

A kinematically complete experiment on the ²H(α, αp)n reaction has been done by using an α-beam of 165 MeV and a liquid deuterium target. The experimental differential cross sections are compared with those calculated in the frame of the impulse approximation. The data indicate the presence of the resonance state of ⁵He.     

A study of the 11B(3He,p)13C reaction at 12, 10, 8, 6 and 4 MeV

Angular distributions for eight proton groups corresponding to states in ¹³C have been measured at incident ³He energies of 4, 6, 8, 10 and 12 MeV. These states are p₀(ground state), P₁(3.09), p₁(3.68), p₃(3.85), p₄(6.86), p₇(7.68), pio(9.50) and p₁₁ (9.90). The angular distributions have been fitted with DWBA analyses using a zero-range approximation. No radial cut-offs were used. In general the data are reasonably well fit at incident energies of 10 and 12 MeV.     

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.     

The polarization of protons from the 2H(d, p)3H reaction for deuteron energies below 1 MeV

The angular distribution of proton polarization P^γ' (θ) from the ${}^2\text{H}\text{(}\text{d,}\text{p}\text{)}{}^3\text{H}$ reaction has been measured at 975 keV deuteron energy. Moreover, the energy dependence of P^γ′(E_d) was measured at 45°(lab) for deuteron energies between 250 and 975 keV. The values of σ₀(θ)P^γ' (θ) were fitted in terms of an associated Legendre polynomial expansion. The measured energy dependence of P^γ' (E_d) has been analyzed in terms of barrier-penetration parameters.     

Large-angle quasi-free scattering in 6Li(p,pd)4He at 670 MeV

The ⁶Li(p, pd)⁴He reaction was investigated at 670 MeV by a coincidence experiment with a large-angle scattering geometry. The energy sharing and angular correlation of the reaction products were measured and the momentum distribution of the recoil nucleus was determined for transitions leading to residual nuclei in the ground and excited states. Results were analysed in terms of a simplified distorted-wave impulse approximation using cluster-model and three-body wave functions. The observed momentum distribution of the p-n pair in the p-shell of ⁶Li is in agreement with three-body calculations, while the spectroscopic factor is larger than predicted by theory. Transitions to breakup states of the α-particle also have the characteristics of quasi-free scattering on deuteron clusters.     

The 3H(t, α)2n reaction at 40 keV

The two-dimensional energy spectrum of the α-particle and the neutron of the ³H(t, α)2n reaction was measured with a small single-gap accelerator at 90 keV. The mean energy of the ³H ions initiating the reaction was estimated to be about 40 keV, i.e. small against the Q-value of 11.3 Me V. It was found that the n-α interaction plays a strong part in the reaction so that no unambiguous determination of a_n-n, the n-n scattering length, was possible. The addition of an n-α final-state interaction to the n-n Jost-function enhancement factor in the analysis greatly improves the agreement with the experimental results, but it was not possible to distinguish between various forms of the n-α enhancement factors nor between different combinations of the n-α and the n-n interactions. The failure to obtain a well established n-n interaction peak is attributed to the absence of a direct reaction mechanism.     

Further study of the reaction 2H(n,p2n) near 120 MeV

A kinematically complete experiment on the reaction ²H(n, p2n) is described, in which both outgoing neutrons were detected at a lab angle of 30° so as to enhance their final state interaction in a region far from interfering reaction mechanisms. The data were analysed in terms of the Watson-Migdal model to obtain two independent values for the neutron-neutron scattering length. We find a_nn to be ?13.3^+3.8_?3.1 fm (from a comparison with measurements of p-d breakup), and ? 17.5_?4.5^+4.0 fm (from the shape of the relative neutron energy spectrum), thus validating the Watson-Migdal model in this kinematic region.     

Proton-proton bremsstrahlung and the 2H(p, 2p)n reaction at 51.8 MeV

Proton-proton bremsstrahlung cross sections were measured at 33°-33° and 8.5°-8.5° with a coplanar symmetric geometry. A comparison between experimental cross sections and theoretical predictions was made. The ²H(p, 2p)n reaction was also investigated at 12.5°–12.5° and 8.5°–8.5°. The cross sections were compared with the values calculated by existing theories.     

Absolute cross sections for the 6Li(p, 3He)4He reaction at energies below 1 MeV

Total cross sections and angular distributions in the ⁶Li(p,³He)⁴He reaction have been measured over the energy range E_p = 100?700 keV. The extrapolation of the cross section to the energy region which is of interest in controlled thermonuclear reactors is given. The values of the “astrophysical S-function” are deduced from the cross sections.     

Study of the 91Zr(d, 3He)90Y reaction

The ⁹¹Zr(d, ³He) reaction was studied at a deuteron energy of 28 MeV. Angular distributions were measured from 13° to 47°; l_p values were extracted for the prominent lines of ⁹⁰Y. The l_p values and transition strengths were determined by DWBA analysis. The angular distributions for the $\text{(π}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ doublet (g.s. and 0.20 MeV state) exhibit the characteristic l = 1 shape. States at 1.42, 1.57, 1.64 and 1.81 MeV were also populated strongly in the (d, ³He) reaction; the 1.42, 1.57 and 1.81 MeV levels contain l= 1 transition strength and are most likely members of the $\text{(π}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ multiplet. The 2.03 MeV state has a characteristic l = 3 angular distribution and is suggested to be the only member of the $\text{(π}\text{f}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ sextet to be unambiguously observed in this study, most probably the 5^? or 4^? member. The members of the $\text{(π}\text{g}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}$ sextet were populated weakly (less than 100 μb/sr) in this reaction.