The Bi(d,γ)Po reaction

The yield of the ²⁰⁹Bi(d, γ)^211g.s.Po and ^211mPo (T_1/2 = 25.2s) reaction was measured for deuteron energies E_d = 8–11.5 MeV. The reaction was identified by the -activities of the Po isotope. At E_d = 10.43 MeV, the (d, γ) cross section for the population of the ground state of ²¹¹Po is σ_g.s. = 16 ± 3 μb, the ratio relative to the cross section for the metastable state is σ_g.s./σ_m = 25.4 ± 0.9. These values and the yield curves were compared with calculations using a simple model for the population of the two states. In the excitation region E* = 15–19 MeV, the branching ratio of γ- to particle emission is nearly constant and has a value of about 0.4 × 10⁻⁴.     

Studies on the Ne(p, d)Ne and Ne(d, p)Ne reactions

Angular distribution measurements have been performed on the ²¹Ne(p, d)²⁰Ne and ²¹Ne(d, p)²²Ne reactions at E_p = 20 MeV and E_d = 10.2 MeV, respectively. In the ²¹Ne(p, d) ²⁰Ne reaction, the prolific formation of the J^π = 2⁺, 1.63 MeV state was characterized by l_n = 2 pickup, and the distribution associated with the 4⁴, 4.25 MeV state was suggestive of a weak l_n = 2 pickup. All of the observed l_n = 1 pickup strength is associated with formation of the 2⁻, 4.97 MeV ²⁰Ne level. The ²¹Ne(d, p)²²Ne results indicate that l_n = 2 transfer is involved in the formation of the 1.28, 3.36, 5.52, 5.63 and 6.65 MeV ²²Ne states. The angular distribution observed for the 2⁺, 4.46 MeV state and also the unresolved 5.33, 5.36 MeV composite of states required both l_n = 0 and l_n = 2 components in the associated distorted-wave Born approximation fits. The spectroscopic factors extracted from the present results are compared with those predicted by the Nilsson model without mixing: Applications of the angular momentum projection rule to the ²¹Ne(d, p)²²Ne reaction are considered.     

DWBA and CCBA analysis of selected transitions in the C(d,τ) B reaction at Ed = 80 MeV

Angular distribution of the reaction ¹²C(d,τ) ¹¹B leading to the 3/2⁻ ground state and the 4.44 MeV excited (5/2⁻ state ¹¹B have measured at E_d = 80 MeV up to about 70° and 40°, respectively. The inclusion of second-order processes in the framework of CCBA calculations gives a good reproduction of the 3/2⁻ as well as of the DWBA forbidden 3/2⁻ angular distribution. The strong dependence of the cross section on the sign of the deformation supports a positive β₂ value for ¹¹B.     

Study of Sc states with proton transfer reactions on Ca

The proton transfer reactions (d, n) and (τ, d) on ⁴²Ca have been studied. The reaction ⁴²Ca(d, n)⁴³Sc has been studied by the time-of-flight method at deuteron energies between 5.0 and 6.05 MeV. The reaction ⁴²Ca(τ, d)43Sc has been studied at 18.0 MeV with a magnetic spectrograph. Altogether 54 levels in ⁴³Sc up to an excitation energy of 6.92 MeV have been identified including states at 4.234 and 6.145 MeV which are analogues of the ground state and the 2.048 MeV state respectively in ⁴³Ca. The l-values and spectroscopic strengths have been determined for 31 transitions. Within the errors of the experiments and the DWBA analyses, the spectroscopic strengths derived from the (d, n) and the (τ, d) experiments are in agreement for both and states, i.e. there are no T-dependent discrepancies. Similar agreement is found in the strengths of the s- and d-hole transitions which reflect the degree of particle-hole impurity in the ⁴²Ca_g,s. wave function. A second state is indicated at 2.657 MeV. It appears a likely candidate for the head of a second band of 6p-3h character as proposed by Johnstone.     

βγ(CP) correlation measurements and anti-analogue structure in the decay of Ca

β-γ(CP) correlation measurements have been carried out on the sequence in the decay of the ground state of ⁴⁹Ca to the (presumed) anti-analogue state at 3.105 MeV excitation in ⁴⁹Sc. An asymmetry parameter of A = −0.132 ± 0.017 was obtained, making any spin-parity assignment other than very unlikely for the 3.105 MeV state. The deduced Fermi matrix element for the decay is |M_{v| = |1.4 ± 9.7| × 10⁻³}, which leads to an isospin impurity ( ) corresponding to the mixing of the analogue state (at 11.6 MeV) and the 3.105 MeV state of ||² 1.6 × 10⁻⁵. This leads in turn to an effective Coulomb matrix element of |H_c| = |3.9 ± 27.4| keV, a low value compared to the value of 100 keV obtained from a theoretical estimate based on simple shell-model wave functions for the single-particle states involved.     

Proximity scattering in the sequential decay Ca(d, n)Sc3.46(p)Ca

In a nuclear two-stage reaction proceeding through excited states of an unstable intermediate system, rescattering can occur between two of the three outgoing particles as a special type of final-state interaction (“proximity scattering”). The probability for proximity scattering increases with a decreasing lifetime of the intermediate state. Correlations between protons and neutrons from the reaction ⁴⁰Ca(d, np)⁴⁰Ca were measured at a bombarding energy of 5.80 MeV and a neutron emission angle of 70°. The results are compared with a quantal calculation of the cross section for this process. A width Γ = 50±20 keV for the excited state at 3.46 MeV in ⁴¹Sc has been deduced from this comparison. Apparent discrepancies between the Γ-values obtained by this method and by a classical prediction for the proximity scattering probability are discussed.     

Cross-section measurements for the reaction B(p, He)Be

Cross sections have been measured for the transitions to the ground state and first excited state of ⁸Be and to the two 2⁺ levels at 16.63 MeV and 16.93 MeV excitation in the reaction ¹⁰B(p, ³He) at E_p = 49.5 MeV. The angular distributions of the cross section were compared with DWBA predictions.     

Excitation of ΔL = 1 resonances in the (p,n) reaction on Zr, Sn, Ce and Pb at Ep = 41 MeV

A broad peak was systematically observed at about 10 MeV above the Gamow-Teller resonance in the ⁹⁰Zr, ¹²⁰Sn, ¹⁴⁰Ce, ²⁰⁸Pb (p,n) reactions at E_p = 41 MeV. The angular distribution shapes of these peaks support the interpretation that they they correspond to ΔL = 1 state. The data are compared with TDA-DWBA calculations.     

The lifetime of the 3.74 MeV (3) state of Ca

The mean life of the 3.74 MeV (3⁻) excited state of ⁴⁰Ca has been directly measured by a particle-gamma delayed coincidence technique. A mean life τ = 59 ± 5 ps was obtained, corresponding to a transition strength B(E3) = 31 ± 3 W.u.     

Energy levels of Si

Proton energies and strengths of (p, γ), (p, p₁), (p, p₂) and (p, ₁γ) resonances of the ²⁷Al + p reaction were determined for E_p < 2.5 MeV. The γ-decay of 78 resonances and 46 bound levels was established and four new bound levels were found at E_x = 9793.8±2.0, 10513.5±1.0, 10884.1±2.0 and 11778.8±1.5 keV. The level at E_x = 11.43 MeV was found to be a doublet. Lifetimes of 25 bound levels were measured by means of the Doppler-shift attenuation technique. Angular distributions were measured at 15 resonances.     

The energy levels of Al

The energies and strengths of ²⁵Mg(p, γ), ²⁵Mg(p, p₁) and ²⁵Mg(p, p₂) resonances were determined in the energy range E_p < 2 MeV. Four new (p, γ) resonances were observed at E_p = 736.2±0.7, 818.1±0.7, 834.6±0.7 and 1514.7±0.7 keV. The γ-decay of 44 resonances and 49 bound levels was established. The energies of 41 and mean lifetimes of 25 bound levels were determined. Two new levels at E_x = 4952.4±1.4 keV and 5141.7±2.0 keV were observed. Angular distributions yielded unique spins for five resonance levels. Weisskopf estimates allowed unique spin assignments for five resonances. The Q-value of the ²⁵Mg (p, γ) ²⁶Al reaction was found to be 6305.0±1.2 keV.     

Investigation of the S(d, p)S reaction at Ed = 10 MeV

Angular distributions of proton groups, corresponding to fifteen levels observed in the reaction ³⁴S(d, p)³⁵S at E_d = 10 MeV have been measured with a split-pole spectrograph equipped with position-sensitive detectors. For the levels at E_x = 0, 1.58, 1.99, 2.34, 2.73, 3.68, 3.80 and 4.20 MeV, l_n = 2, 0, 3, 1, (2, 3), (1), 1 and 1, respectively, has been found from a DWBA analysis. Experimental spectroscopic factors and those following from many-particle shell-model calculations for the lowest four states are in satisfactory agreement. The ground state Q-value has been measured as Q = 4757 ± 5 keV.     

Proton occupation numbers for Ca

The (d, ³He) proton pickup reaction on ⁴⁴Ca has been studied at a deuteron energy of Ed = 19.0 MeV using the Minnesota MP Tandem Van de Graaff. Differential cross sections were measured at forward angles and spectroscopic factors were extracted in the usual fashion for the transitions to five states of ⁴³K. The results are compared with previous proton pickup and stripping reactions on the even Ca isotopes. Only about half of the sd hole state excitation strength observed in the stripping reactions could be found in the pickup from the fp orbitals if the data are analyzed by standard distorted wave calculations. This discrepancy can be removed by using bound state potential radii which are slightly larger for sd orbitals than for fp orbitals.     

Spin-dependent reaction mechanism in Ti(d, p)Ti from proton-γ correlation

The γ-decays of the states in ⁴⁷Ti at 157 keV and 1547 keV have been studied following the ⁴⁶Ti(d, p)⁴⁷Ti reaction at 5.0 MeV incident energy. Protons were detected at 0° with a semiconductor detector. The angular correlations of the γ-rays with the reaction protons were measured. The E2/M1 mixing ratios of the γ-decays and the population ratios of the to the substates were deduced. From the non-zero population of the substate it was concluded that a spin-flip mechanism exists in the ⁴⁶Ti(d, p)⁴⁷Ti stripping reaction.     

The (1f7/2) multiplet in Ca

The states of ⁴²Ca below 3.2 MeV excitation are studied by the ⁴¹Ca(d,p)⁴²Ca reaction at 12 MeV bombarding energy. The experimental spectroscopic factors are compared to predictions based on Gerace and Green's coexistence model.     

A study of the Li(π, pp)He reaction within the three-body problem

The differential cross section for the ⁶Li(π⁺, pp)⁴He reaction for symmetrical coplanar kinematics has been calculated at the incident pion energy E_π = 70 MeV within the three-body problem + 2N taking into account the Pauli exclusion principle in each N subsystem. Three-body distortions in the final state have been taken into account in the eikonal approximation. The treatment is based on the superposition of the single-particle and two-particle mechanisms of absorption leading to the rescattering of the π- and ρ-mesons through the Δ-isobar. The analytical character of the adopted wave function for the ⁶Li nucleus (the multidimensional gaussian basis) makes it possible to ascertain clearly that the reaction amplitude of the type under study is insensitive to short-range NN correlations both in the initial and final states. The calculated momentum distribution of recoil -particles is in good agreement with the experimental data available, but the experimental accuracy should be improved in order to see the contribution of a specific three-body part of the ⁶Li wave function orthogonal to the ad channel. Some problems to be solved in future are discussed.     

Proton polarization observables for the elastic and inelastic scattering of 500 MeV protons from Ca and Pb

Measurements for the elastic and inelastic scattering of 500 MeV protons from ⁴⁰Ca and ²⁰⁸Pb at small momentum transfers are reported. The induced proton polarization P and the spin rotation parameter Q were measured for the elastic scattering. The spin rotation parameters D_SS′, D_SL′, D_LL′, d_LS′ and the induced polarization P were measured for transitions to the 3⁻(3.37 MeV) and 5⁻(4.48 MeV) states in ⁴⁰Ca and the 3⁻(2.61 MeV) state in ²⁰⁸Pb. Comparisons of the data with the theoretical calculations were carried out in the framework of nonrelativistic and relativistic approaches. We extracted the spin-up and spin-down channels for the elastic scattering cross sections and found that predictions of the relativistic and nonrelativistic approaches agree well with the spin-up channel data and differ considerably in the spin-down channel.     

The (He, t) reaction at intermediate energies : Spin-isospin multipole transitions

Data for the (³He, t) reaction at 900 MeV and 2 GeV on the targets ²⁶Mg, ⁴⁰Ca, ⁴⁸Ca, ⁵⁴Fe, ⁹⁰Zr and ²⁰⁸Pb are presented. A multipole decomposition for the data at 900 MeV has been made and the different distributions have been analysed. From the L = 0 cross section the Gamow-Teller strength distributions are extracted and compared with (p, n) data. The L = 1 and 2 distributions are analysed in a schematic model which describes the general systematics fairly well. The spectra at 2 GeV and Θ = 4° show for all targets a well-developed quasi-elastic peak. The A-dependence of the cross section is analysed in a simple model.