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

Abstract

Spin ½ 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 ½is one of the reasons it has become so useful as a magnetic probe. Until now there has been no spin ½probe 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 Be, which is the lightest spin ½ isotope suitable for β-NMR. The intensity of the 11 + beam―generated by a laser ionisation source― is about 10 6 /s. The Be 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 Be + at 313 nm.