L.A. Beach

Angular distributions and cross-section ratios for the reactions 2H(d, n)3He and 2H(d, p)3H below 500 keV

Abstract The competing reactions 2H(d, n)3He and 2H(d, p)3H were remeasured over the bombarding energy range of 20 keV to 350 keV with a magnetically analysed beam incident on a gas target. The angular distributions of the charged reactions products were observed with surface barrier detectors at 10° intervals 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 and Legendre polynomials are obtained showing greater asymmetry in the neutron producing reaction. Branching ratios between the two reaction modes monotonically increase over this energy range with the neutron reaction favoured above a bombarding energy of 30 keV. A theoretical analysis of these branching ratios and asymmetry coefficients indicate the mass radius of the 3H nucleus is at least 8.5% smaller than that of the 3He nucleus.

Quasifree processes in the 2H + 3He interaction

Abstract Quasifree scattering and quasifree reaction processes have been examined in the 3 He+ 2 H → p+d+d, 3 He + 2 H → n+p+ 3 He and 3 He+ 2 H → 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.

Two-spectator quasifree processes

Abstract Two-spectator quasifree processes (graphs with two spectator particles) for the 3 He( 3 He, dd)pp reaction at the symmetric angle pairs θ = 30.1° at E 3 He = 50 MeV and θ = 37° at E 3 He = 78 MeV are investigated. The theoretical cross sections are calculated with the PWIA model. The measured cross sections are smaller but have shapes which are in good agreement with the calculation. The ratio N = experiment/theory is approximately 0.05 at 50 MeV and 0.1 at 78 MeV. The reaction 2 H(d, pp)nn also was studied at the symmetric angle pair θ = 34.8° and E 2 H = 34.7 MeV and the ratio is about 0.14.

Study of the (p, pn) reaction in light nuclei

Abstract The (p, pn) reaction on 2H, 6Li, 7Li, 9Be has been studied at 47 MeV bombarding energy. Excitation energy spectra and energy sharing spectra are presented. Fragmentary information on 10B, 11B and 12C was also obtained. Sequential decay contributions to the 6Li(p, pn)5Li∗ reaction suggest an admixture of parentage (α)π( p 1 2 )π( d 5 2 ) for the (3−), 23 MeV excited state of 6Be. A possible 15.5 MeV excited state in 6Be is reported. An extensive study of the 9Be (p, pn)8Be reaction for 45 MeV protons was made. Results for θp = θn = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θn = 40°, θp = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θp/θn = 40°/45°, 38.5° are reported and compared to DWIA calculations. Agreement is good when the lower momentum components of the wave function are sampled, and deteriorates as higher momenta are required. Results are in agreement with the Cohen and Kurath spectroscopic factors for 9Be.

Quasifree processes in the3He+3Hand3He+3He interactions

Abstract Quasifree scattering and quasifree reaction processes have been examined in ten 3 H + 3 He and 3 He + 3 He reactions with at least two of the three or more final state particles being charged. Beam energies of 50, 65 and 78 MeV were used. The experimental results are compared with PWIA predictions and Fourier transforms of the wave functions are extracted. The quasifree processes are described in a consistent, but qualitative, manner by the PWIA; distortion in the intial state appears to be the cause of the consistent deviation of the data from the PWIA predictions. Extracted values for the 3 H(d, 3 He)2n cross section are given.

QUASIFREE PROCESSES IN THE REACTION 3He + 3He FOR E3He = 50, 65 and 78 MeV

This chapter discusses quasi-free processes in the reaction 3 He + 3 He for E 3He = 50, 65 and 78 MeV. There are several three-particle breakup combinations that can occur when 3 He bombards 3 He. Measurements for a number of quasifree scattering (QFS) and quasifree reactions (QFR) interactions for 3 He + 3 He have been obtained in kinematically complete experiments. Charged particle pairs are detected and conditions are chosen favoring the observation of quasifree processes. The data are analyzed in terms of the plane-wave-impulse-approximation with the Hulthen wave function. In a study described in the chapter, gas cell target and fixed detector-aperture geometry was used. The effective target thickness and detector solid angles were calculated. The calculations were compared to measurements of the product of these parameters from 2 H(p,p) 2 H and 2 H(p,pp)n two- and three-body reactions for E =22 MeV where the d 2 σ and d 3 σ are well known.

QUASIFREE PROCESSES IN THE 2H + 3He REACTIONS

This chapter discusses quasi-free processes in the 2 H+ 3 He reactions. In the interaction between 3 He and 2 H, there are several three-particle breakup combinations possible. Kinematically, complete measurements were obtained with 2 H beam energies of 22.3 and 35 MeV and 3 He beam energies of 30.0, 33·4, and 52.5 MeV. Charged particle pairs were detected with conditions favoring the observation of quasi-free processes, both quasi-free scattering (QFS) and quasi-free reactions (QFR). The d + d, p + d, and 3 He + p QFS interactions and the 3 He + n→ p + t, d + d → p + t, and 3 He + n → d + d QFR interactions were observed. The chapter presents the analysis of data for a given interaction and comparison of a plane-wave-impulse-approximation prediction. The momentum wave function is extracted for small values of spectator momentum. Data were acquired primarily with a gas cell target having either 2 H or 3 He gas and fixed detector-aperture geometry. The results indicate that there is little difference in d 3 σ (exper)/d 3 σ (PWIA) as a function of beam energy (incoming channel CM energy), and this ratio does not depend on whether the spectator is in the projectile or in the target.

THE N-P FSI ANGULAR DISTRIBUTION IN DEUTERON BREAKUP AT 45 MeV

Publisher Summary This chapter reviews the N–P Final State Interaction (FSI) angular distribution in deuteron breakup at 45 MeV. An experiment described in the chapter was performed to provide an FSI angular distribution at energy higher than previously available. The experiment was performed with the NRL Sector Focusing Cyclotron using standard coincidence electronics for kinematically complete experiments. The chapter presents a comparison of the data with the results of calculations using several S-wave separable potentials tailored to test for sensitivity to off-shell and on-shell effects. These potentials have been described previously. The potentials have two different form factors A and B: A has off-shell behavior similar to that of the Reid soft core potential while B has off-shell behavior resembling the softer Yamaguchi. The potentials fit two different sets of phase shifts: set 1 corresponds nearly to experimental p–p 90° cross sections and set 2 corresponds to cross sections less than the p–p experimental values at energies above 10 MeV. The results, when put in the context of previous experiments and calculations, emphasize that there are still some basic factors not being considered in deuteron breakup calculations.

DOUBLE SPECTATOR PROCESS IN THE 3He(3He, dd)pp REACTION

Publisher Summary This chapter examines the double spectator process in the 3He(3He,dd)pp reaction. Measurements of nuclear systems with three or four particles in the final state can be influenced by a number of processes: (1) quasifree scattering (QFS), (2) quasifree reactions (QFR), (3) final state interactions (FSI), (4) simultaneous breakup, which results in phase space distribution of events, and (5) second-order effects. The chapter describes an investigation on the four-body continuum for the reaction 3He(3He,dd)pp with two detector-telescopes in coincidence to determine whether the double quasifree scattering (DQFS) process is observable. The 3He(2H,dd)p and 2H(3He,dd)p reactions were also measured for DQFS-equivalent d–d center of momentum conditions with proton spectators in the target and projectile, respectively. The results obtained suggest that the DQFS process is observable, and the comparison of the data to PWIA predictions indicate that 3He has a reasonably strong p + d cluster configuration and that a PWIA analysis is as appropriate for DQFS processes as it is for QFS processes.

A P-D FINAL STATE COULOMB INTERACTION FROM 2H(α,dt) 1H WITH Eα = 70 MeV

Publisher Summary This chapter describes that in a coplanar, kinematically complete experiment, the evidence for a strong p–d final state Coulomb interaction (FSCl) was observed with the 2 H(α, dt) 1 H reaction. Identified particle and coincidence energy information for d and t with various angle pairs was obtained. Such an experiment has the distinct advantages of determining the kinematics of the final state and of distinguishing the final state interaction of interest from other interactions and sequential or quasi-free scattering processes. These advantages have made the application of the Watson–Migdal formalism and other appropriate formulations quite successful in predicting the shape of the spectral structure. In this particular experiment, comparison of theoretical predictions to the data is constrained by the low counting rates encountered and the presence of spectral structure. Though the chapter does not explain the three-body final state cross section for multiparticle breakup experiments with sequential and FSI processes, it explains the factors that contribute to the cross section. The presence of sequence and the insensitivity of the fitting to the effective range parameters limit the interpretation of the p–d FSI. The fits generated suggest that no 3 He excited state exists near its p–d breakup threshold.