<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>breakup of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Li</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>7</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Li</mml:mi></mml:math>near the Coulomb barrier

Angular distributions of the $\ensuremath{\alpha}$-particle production differential cross section from the breakup of ${}^{6}\mathrm{Li}$ and ${}^{7}\mathrm{Li}$ projectiles incident on a ${}^{208}\mathrm{Pb}$ target have been measured at seven projectile energies between 29 and 52 MeV. The $\ensuremath{\alpha}$-breakup cross section of ${}^{6}\mathrm{Li}$ was found to be systematically greater than that of ${}^{7}\mathrm{Li}$ across the entire energy range. These data have been compared with previously reported results and with the predictions of continuum-discretized coupled channels (CDCC) calculations including resonant and nonresonant projectile breakup. The present data compare well with previous measurements, while the CDCC calculations provide a reasonable prediction of the relative $\ensuremath{\alpha}$-breakup cross sections but underpredict their absolute values. The calculations confirm that a major factor in the enhancement of the ${}^{6}\mathrm{Li}$ to ${}^{7}\mathrm{Li}$ $\ensuremath{\alpha}$-breakup cross section is the difference between the $\ensuremath{\alpha}$-breakup thresholds of the two isotopes. These results have implications for structural studies of light exotic nuclei based on elastic scattering.