Search

A number of 6 − and 5 − states in 26 Al were studied in the region of excitation energy 5–15 MeV with the 24 Mg(α, d) 26 Al reaction at E α = 63.7 MeV. The data were analyzed within the framework of zero-range DWBA theory for a macroscopic deuteron-cluster transfer as well as for a microscopic two-nucleon transfer, and compared with our previous results on the 25 Mg( 3 He, d) 26 Al reaction. Several 6 − and 5 − states are newly proposed. Five 6 − states previously assigned as T = 1 were weakly observed in the present (α, d) reaction, which should excite only T = 0 states. The isospin breaking (α, d) transition to the 6 − 1 , T = 1 state was found to be an order of magnitude larger than a second-order exact-finite-range DWBA calculation for the successive transfer processes of ( α - 3 He-d) and ( α -t-d).

Differential cross sections and analyzing powers have been measured for (p, d) reactions on 1p, 2s, 1d, 2p, 1g and 2d shell nuclei with 65 MeV polarized protons. The analyzing powers clearly show a j -dependence which depends on the numbers of nodes in the radial wave function of the neutron. The shapes of the angular distributions of the analyzing powers can be classified into five types for simple neutron pickup reactions from the 1p−2d shells. The pickup from the 1 p 1 2 shell is singular.The DWBA calculations have been carried out on these (p, d) reactions in order to interpret the j -dependence. Adiabatic deuteron optical potentials can describe the data better than those derived from the deuteron elastic scattering except for the pickup from the 1 p 1 2 shell. The analyzing powers for the 1 p 1 2 shell neutron pickup can be reproduced only when large values of the radius and diffuseness parameters are used in the bound-state potential.

The in-plane α-α angular correlation of the reaction 12C(α, α')12C(4+)(α)8Be(0+) has been measured at an incident energy of 65 MeV. The correlation data were analyzed by coupled channel calculations on the basis of a rotator model. A strong sensitivity of the correlation function to the sign of the quadrupole and hexadecapole deformation parameters was found. The deformation parameters for 12C were determined to be β2 = −0.40±0.02 and β4 = +0.16±0.03.

High spin states in the 2s-1d shell nuclei of 18F, 20F, 22Na, 24Na, 26Al, and 30P have been investigated by (α, d) reactions at incident energies of 64.3–65.3 MeV. The ( f 7 2 ) 2 7 + states in 20F, 22Na and 24Na, and the ( f 7 2 d 5 2 )6 − states in 20F and 24Na are proposed. The systematic dependenc of the Q-value and intensity on the mass number for the (α, d) reaction leading to the 5+, 6−, and 7+ states is obtained. For the 7+ states, the dependence of the Q-values on the mass number in the mass region below 26 deviates from the line expected from the results of heavier 2s-1d shell nuclei. The excitation energies of the ( f 7 2 ) 2 7 + states expected from a crude shell-model calculation are in good agreement with the experimental data. Using the Q-values for the 7+ states and empirical binding energies for the single-particle f 7 2 shell orbit, a mass dependency of the p-n interaction energies for the ( f 7 2 ) 2 7 + configuration has been found to be E[( f 7 2 ) 2 7 + ] = − 100 A of these 2s-1d shell nuclei.

The reactions ( 3 He, t), ( 3 He, 3 He), ( 3 He, α) and ( 3 He, d) on 48 Ca have been studied at an incident energy of 82 MeV. The obtained angular distributions for the ( 3 He, t) reaction have been analyzed in terms of second-order DWBA theory, using a zero-range approximation. The relative ratio of the cross sections for the excitation of the f in 7 2 f 7 2 −1 multiplets of 48 Sc could not be explained consistently by the one-step charge-exchange process only. However, the ratio was reproduced in order of magnitude by second-order DWBA calculations including the effect of two-step processes, such as ( 3 He-α-t) and ( 3 He-d-t) channels. The effects of the d- and α-channels on the elastic scattering of 3 He from 48 Ca were also examined in the framework of second-order full finite-range DWBA.

Level structure of 76 Kr has been studied with the 78 Kr(p, t) 76 Kr reaction. Several low-lying levels were observed for the first time and the previously unknown mass excess of 76 Kr was measured to be 68 968 ± 15 keV. The measured angular distributions were compared with the predictions of DWBA calculations and the spin-parities of some of the levels are proposed. The level structure of 76 Kr are compared with those of other N = 40 isotones, and discussed in terms of several nuclear models.

The 27 Al(α, t) and (α, 3 He) reactions have been measured at E α = 64.5 MeV. The experimental angular distributions were analyzed by the exact finite-range DWBA calculations assuming a nucleon stripping mechanism. The distributions of spectroscopic strengths for the single-particle transitions with transferred angular momenta l = 0, 1, 2, 3 and 4 have been obtained. The strengths for the transitions to the stretched 6 − states in 28 Si and 28 Al are compared to those obtained from inelastic scattering on 28 Si. The present results show no distinctive differences in the structures for 6 − T = 0 and 1 states in 28 Si such as are observed in proton and pion inelastic scattering on 28 Si.

The 24, 26 Mg( 6 Li, d) 28, 30 Si reactions have been studied at 73 MeV bombarding energy. The angular distributions were analyzed with exact finite-range distorted wave Born approximation calculations assuming a direct α-cluster transfer. Extracted spectroscopic strengths leading to low-lying levels of 28 Si and relative spectroscopic strengths between transitions to 28 Si and 30 Si ground states are consistent with those previously obtained by several α-transfer reactions. Many strongly populated levels have been observed at E x ≳ 10 MeV for 28 Si. A marked similarity was found between the deuteron spectrum and the 24 Mg(α, α) 24 Mg excitation function in this excitation energy region. A brief comparison of the present α-transfer results with previous two-nucleon transfer data leading to 28,30 Si is also presented.

Differential cross sections and vector analyzing powers were measured for the (d, p) reaction with 56 MeV polarized deuterons. The investigation covered the transitions to the single-particle states of the 1p. 2s, 1d. 2p, 1f, 3s, 2d and 1g shells. The analyzing powers showed a j -dependence which depended on the number of nodes in the radial wave function of the transferred neutron. DWBA and adiabatic model calculations were carried out. The DWBA calculations reproduced the experimental cross sections and analyzing powers for the stripping to the j > states. The adiabatic model did not necessarily improve the fits to the data for these transitions. As for the j transitions, on the other hand, the DWBA calculations could not reproduce the experimental angular distributions, while the adiabatic model calculations improved the agreement with the experimental data.