11Li is the first-discovered and best-known example of a halo nucleus. It consists of a core of 9Li surrounded by a two-neutron cloud, or “halo”, that gives it a nuclear matter radius similar to that of a lead nucleus. While this in itself should not affect the charge radius of 11Li since the halo is composed entirely of neutral particles, experiments at TRIUMF-ISAC have measured a charge-radius significantly larger than that of 9Li. This indicates that the presence of a halo somehow deforms the nuclear core—a change that would manifest itself as an increase in the nuclear quadrupole moment Q from one isotope to the next. Currently accepted values for these moments provide evidence for this, giving a ratio between the two of Q11/Q9 = 1.088(15). Unfortunately, these moments are not known very precisely, and large differences exist between the predictions of their values by different theoretical models, necessitating that a more accurate experimental measurement of this nuclear property be made. This experiment therefore sets as its ultimate goal the measurement of the Q11/Q9 ratio to as high a precision as possible, using the technique of β-NQR spectroscopy. TRIUMF-ISAC is well-suited to perform this experiment since it currently produces the highest-intensity 11Li beam in the world, and already contains all the needed experimental tools.
 Sánchez et al., 2006 Phys. Rev. Lett. 96, 033002  Neugart et al., 2008, Phys. Rev. Lett. 101, 23502