⁴He D-State Effects in the ²H(d/γ) ⁴He Reaction at Low Energies

Abstract

Large tensor force effects have recently been reported in the ²He(d,γ) ⁴He reaction induced by polarized deuterons [1,2,3]. For deuteron energies E_d < 20 MeV the reaction is dominated by the E2 transition. Among the allowed E2 amplitudes A = < ⁴He|E2|¹D₂ > is essentially determined by the He S-state, and B= < ⁴He|E2| ⁵S₂ >, C= < ⁴He|E2| ⁵D₂ >, D= < ⁴He|E2| ⁵G₂ > by the ⁴He D-state. It is well known [2] that the angular distributions of the tensor analyzing powers (TAP) are very sensitive to the value of the asymptotic D/S state ratio P in the d+d cluster configuration of He. This effect can be observed for deuteron energies near 10 MeV where the dominant amplitudes are A and C. As the deuteron energy decreases, the transition amplitude from the ⁵S₂ scattering state becomes dominant due to the absence of the centrifugal barrier. The amplitudes B and A become of the same order of magnitude while C is negligible. Therefore large D state effects are also expected at low energies and the sensitivity to P can be observed either in the TAP or in the cross section [4].