The mechanism of the (p, α) reaction: Pick-up or knock-out?

Several early studies of the (p, α) reaction to discrete states of the final nucleus indicated that it proceeds mainly by the pick-up mechanism, whereas more recent experiments provide qualitative arguments in favour of the knock-out mechanism. This paper reports calculations showing that the angular distributions and analysing powers of the^90,92Zr(p, α)^87,89Y and¹¹⁸Sn(p, α)¹¹⁵In reactions can be equally well fitted by distorted wave calculations using either mechanism.