Spin polarization of ${}^{37}\mathrm{K}$ nuclei produced via single proton pickup from a ${}^9\mathrm{B}\mathrm{e}$ target by a beam of $150\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}$ ${}^{36}\mathrm{A}\mathrm{r}$ has been observed. Positive spin polarization with magnitude $(8.5\pm 0.6)\%$ was deduced near the peak of the ${}^{37}\mathrm{K}$ momentum distribution. The variation of the spin polarization as a function of outgoing ${}^{37}\mathrm{K}$ momentum is explained by a classical conservation model, as previously applied to describe the induced spin polarization observed for fragments produced in intermediate-energy heavy-ion reactions, with the condition that the picked-up proton has an average momentum equal to the Fermi momentum and is aligned along the incident beam direction.

• Received 23 January 2003

DOI:https://doi.org/10.1103/PhysRevLett.90.202502