(d, a) reaction and the a particle D state

There is great interest in the technique of using transfer reaction observables to investigate aspects of the internal structure of composite projectiles. The work of Johnson, ' which showed the sensitivity of calculated tensor analyzing powers to the D-state component of the relative motion of the transferred (x) and residual (b) clusters in the projectile (a), has led to extensive experimental testing of our theoretical knowledge of the twoand three-body systems via the (d,p), ' (d, t), and (d, 'He) (Refs. 3 and 4) reactions. The quantity to which these data are primarily sensitive is the number D2(b, a), in the notation of Ref. 5, which, for weakly bound clusters, is closely allied to the asymptotic Dto S-state ratio of the radial wave functions for the b-x relative motion. Santos et al. suggest' that, similarly, available (d, a) tensor analyzing power data, on sd-shell nuclei at 16 MeV, 8 display the signature of a D-state component of the o. particle, The process envisaged by Santos et a/. , and that used in this Rapid Communication, is that the reaction takes place as the one-step transfer of a real deuteron, so that, in the context of the distorted-wave Born approximation (DWBA), the D-state component referred to is the / = 2 component of relative motion of two deuterons in the o. particle. That is, the D-state part of the overlap~