High spin states of 2s-1d shell nuclei excited by (α, d) reactions

Abstract

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 ) 27 + 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 ) 27 + 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 ) 27 + configuration has been found to be E[( f 7 2 ) 27 +] = − 100 A of these 2s-1d shell nuclei.