E.L. Petersen

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.

Quasi-free scattering in the D(p, pn)p reaction from 15 to 50 MeV

Abstract The D(p, pn)p reaction was studied in a kinematically complete experiment. Comparison with the kinematically equivalent D(p, pp)n reaction shows the surprising result that the measured cross section for the (p, pn) reaction is a factor of seven larger than that of the (p, pp) reaction at the lower energies. The impulse approximation describes the shape of the observed energy spectra, but does not predict the measured magnitude.

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.

The 2H(p, 2p)n reaction at Einc = 45 MeV and its sensitivity to various separable S-wave N-N potentials

Abstract This paper presents and analyses the data for the 2 H(p, pp)n reaction at E inc = 44.9 MeV. Kinematic conditions including the quasi-free scattering region and the regions far from quasi-two-body processes are considered. The experimental results are compared with the predictions of several separable S-wave models of the N-N interaction. Potential models that differ only off-shell, as well as models that predict different N-N scattering results are included to help to isolate aspects of the break-up reaction sensitive to off-shell and on-shell differences. The regions far from quasi-free scattering are generally much more sensitive to the off-shell features of the interaction than are quasi-free scattering results. On-shell differences in the potential affect predictions in all regions of phase space with the potentials best representing the free N-N data giving the best overall fit to the data over most regions of phase space.

Sequential decay in the 7Li(α, t)8Be(α)4He and 7Li(α, α')7Li∗(t)4He reactions at Eα = 50 MeV

Abstract The 7 Li (α, t) 8 Be (α) 4 He and 7 Li (α, α) 7 Li ∗ ( t ) 4 He reactions have been observed in a kinematically complete experiment with E α = 50 MeV, particle identification, and on-line computer coincidence electronics. Sequential decay through the ground, 2.9, 11.4, 16.6 and 16.9, and 19.9 MeV states of 8 Be and the 4.63 and 7.48 MeV states of 7 Li has been observed. Triton angular distributions for the decay through the ground state of 8 Be were obtained with and without coincidence requirements. Agreement of these distributions implies isotropic decay in the c.m. of the 8 Be ground state. The contribution of quasi-elastic processes is small due to the specific limited portion of phase space observed.

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.