Polarisation of a spin–NMR probe 11Be using collinear laser optical pumping

Spin 1 2 probes have special importance in the field of NMR, since they have no electric quadrupole moment and are thus pure magnetic sensors. The absence of quadrupolar splittings greatly simplifies the \{NMR\} frequency spectrum. That the muon is spin 1 2 is one of the reasons it has become so useful as a magnetic probe. Until now there has been no spin 1 2 probe suitable for beta-detected NMR. Such a probe would be particularly useful in complex materials, which are in general non-cubic. In this paper we describe the development of a low energy beam of spin-polarised 11Be, which is the lightest spin 1 2 isotope suitable for β -NMR. The intensity of the 11 Be + beam—generated by a laser ionisation source—is about 10 6 / s . The 11Be nuclei are polarised by collinear laser optical pumping with an externally frequency doubled dye laser tuned to the 2 S 1 / 2 –2 P 1 / 2 transition of 11 Be + at 313 nm.