Model independent determination of the spin of the 180Ta naturally occurring isomer

The hyperfine structures of the 33715.27 cm(-1) and 33706.47 cm(-1) transitions from the ground state of singly ionized Ta have been measured by collinear laser spectroscopy. The structures were found to contain a large second order contribution. From fitting the observed hyperfine components for both Ta-181 and the Ta-180 naturally occurring isomer it was possible to determine the first and second order hyperfine structure coefficients. As no model independent determination of the nuclear spin of the Ta-180 isomer has been performed, fitting was attempted for a range of spins. A clear chi-squared minimum is obtained for a nuclear spin of 9, in agreement with model dependent measurements.