Search

The cross section and the analyzing powers Ay, Axx, Axz and Ayy for the reaction H ( d , 2 p ) n are studied by kinematically overdetermined measurements at an incident energy of 16 MeV at collinear and somewhat off-collinear kinematic conditions. A three-body Faddeev model using two realistic separable potentials that have different short-range parts gives a good fit to the data. Uncertainties in Coulomb corrections make it difficult to draw definitive conclusions about possible three-nucleon force effects at collinearity conditions.

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.

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.

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.

The cross section and the analyzing powers A y , A xx and A yy for the reaction 4 He( d , αp)n are studied with kinematically complete measurements at incident energies of 12 and 17 MeV. Spectral structures due to the final-state interactions and quasifree scattering are measured. A three-body model of the Faddeev type gives a satisfactory fit to the cross-section and A y data, but it fails to fit adequately the tensor analyzing-power data. The tensor analyzing powers in the breakup process should be sensitive to the input two-body force, and that sensitivity seems to be somewhat greater near the three-body 1 + resonance.

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.

Approximately 50 resonances having a yield of greater than 100 gamma rays per μC were discernible from the 62Ni(p, γ)63Cu reaction in the range of proton energy from 1100 keV to 1850 keV. Gamma-ray energy measurements obtained by utilizing scintillation and lithium-drifted silicon spectrometers yield 3.42±0.02 MeV and 6.14±0.02 MeV for the Q-value of the 58Ni(p, γ)59Cu and 62Ni(p, γ)63Cu reactions, respectively. The existence of intermediate states was observed in 59Cu at 0.49±0.01, 0.91±0.01, 1.38±0.02, 2.00±0.02 and 2.32±0.02 MeV; and in 63Cu at 0.67±0.01 and 1.55±0.02 MeV. Triple-correlation measurements were performed with a double sum-coincidence spectrometer at resonance energies of 1424, 1663 and 1715 keV for the 58Ni(p, γγ)59Cu reaction and at resonance energies of 1374, 1414, 1507 and 1634 keV for the 62Ni(p, γγ)63Cu reaction. These measurements permitted Jπ assignments of ( 1 2 ), 5 2 − , 5 2 − , 5 2 − and ( 3 2 − ) or ( 5 2 − ) to the intermediate states in 59Cu at 0.49, 0.91, 1.38, 2.00 and 2.32 MeV, respectively; and ( 1 2 ) and either ( 3 2 − ) 5 2 − ), or ( 3 2 + ) to the intermediate states in 63Cu at 0.67 and 1.55 MeV, respectively. The E2/M1 amplitude ratios were obtained whenever possible from the correlation data.

The 7 Li (τ, α) 6 Li and 7 Li(τ, α) 6 Li∗(d) 4 He reactions have been used to study the energy levels of 6 Li. Singles spectra provide evidence for five states below 6 MeV of excitation energy. These include the ground state and four excited states at 2.18, 3.56, 4.57 and 5.36 MeV. One- and two-parameter coincidence data confirm the identification of these levels and aid in the determination of decay modes and isospin assignments. The deduced isospin assignments for the five levels are T = 0, 0, 1, 0 and 1 with a small T = 0 impurity, respectively.

The (α, α') and (p, p') reactions have been used to populate states in 24 Mg in order to measure lifetimes of ten states by the Doppler-shift attenuation method. The shifted γ-rays were observed by a planar 5.6 cm 3 Ge(Li) detector at 90° to the beam at the target in coincidence with the scattered particles observed in either of two particle detectors located symmetrically with respect to the beam. A computer coupled dual two-parameter arrangement permitted concurrent measurements for all states appreciably populated. The present measured transition probabilities are compared with predictions from a truncated j - j coupling shell-model calculation.

The α-α angular correlation from the sequential decay of the 11 B(p,α) 8 Be 2.9 (α) 4 He reaction indicates that this reaction proceeds by compound-nucleus formation of 12 C states of E x , J π = 16.11(2 + ), 16.58(2 − and 17.23(1 − ). For E p = 0.163, 0.675, 1.00 and 1.39 MeV, and for a first-emitted α-partiele angle of 90°, kinematically complete experiments provide observed symmetry axes for the 8 Be 2.9 break-up distribution in its own c.m. system. The axis for each correlation function, when compared to the momentum transfer and recoil directions associated with various possible mechanisms, indicates that compound-nucleus formation is the predominating mechanism at each beam energy. The correlation functions at the resonant proton energies of 0.163, 0.675 and 1.39 MeV are consistent with the capture states having J π = 2 + , 2 − and 1 − , respectively.