Determination of the asymptotic D- to S-state ratio for ⁶Li via (⁶Li→,d) transfer reactions

Measurements of cross section, vector analyzing power A_y, and tensor analyzing powers A_zz and A_xz over the angular range 10°<~θ_lab<~40° have been performed at E(⁶Li)=34 MeV for the ⁵⁸Ni(⁶Li→,d)⁶²Zn and ⁴⁰Ca(⁶Li→,d)⁴⁴Ti reactions leading to the ground state and first excited state of both residual nuclei. The reactions are described by distorted-wave Born approximation calculations, assuming a direct α-particle transfer mechanism. The asymptotic D/S state ratio η for the d+α relative wave function in ⁶Li is determined. In this one-step analysis, the best fit to the tensor observables leads to a value of η=+0.0003±0.0009. This value is in disagreement with most of the previous theoretical and empirical determinations of η. An investigation of two-step reaction mechanisms is performed, allowing the J^π=3⁺, 2⁺, and 1⁺ states in ⁶Li to contribute to the transfer reaction channel. Reasonable agreement is achieved with the cross section and vector analyzing power data for several possible two-step amplitudes. It is found that the fitted magnitude of η increases with increasing two-step amplitude, giving η=-0.0030±0.0022 for unit amplitude, therefore not changing significantly from our one-step result.