  We have produced laser-cooled Wigner crystals of 229Th3+ in a linear Paul
trap. The magnetic dipole (A) and electric quadrupole (B) hyperfine constants
for four low-lying electronic levels and the relative isotope shifts with
respect to 232Th3+ for three low-lying optical transitions are measured. Using
the hyperfine B constants in conjunction with prior atomic structure
calculations, a new value of the spectroscopic nuclear electric quadrupole
moment Q = 3.11(16) eb is deduced. These results are a step towards optical
excitation of the low-lying isomer level in the 229Th nucleus.
