The tensor analyzing power $A_{\mathrm{yy}}$(θ), vector analyzing power $A_y$(θ), and cross section σ(θ) of the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d→,γ${)}^4$He reaction have been measured for the angular range of 55°–149° in the center of mass system at an incident deuteron energy of 95 MeV. The reaction is dominated by the ${〈}^1$$D_2$‖E2${\Vert }^1$$S_0$〉 transition involving the S-state component of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, as indicated by the approximately ${\sin }^2$2θ angular distribution of the cross section. The observed deviation of σ(θ) from this shape is due to either M2 strength, tensor force effects, or both. The tensor analyzing power $A_{\mathrm{yy}}$(θ) is nearly isotropic, with a typical value of approximately 0.3±0.1. The vector analyzing power $A_y$ is zero within the statistical precision (typically ±0.2) of this data set, indicating a reduced contribution from E1 and M2 transitions compared to lower energies. Direct capture calculations in the plane-wave Born approximation do not reproduce even the sign of $A_{\mathrm{yy}}$.

• Received 6 September 1988

DOI:https://doi.org/10.1103/PhysRevC.39.1679