We use recently measured cold photoassociation and two-photon data to
extract the singlet and triplet accumulated radial phases of interacti
ng ground-state lithium atoms. Using the resulting values we predict s
cattering lengths, Feshbach resonances, and exchange decay rates for c
old collisions between Li-7 and Li-6 atoms that are of interest for th
e possibility of sympathetic cooling of Li-6 and for the coexistence o
f the bosonic and fermionic quantum-degenerate phases of Li-7 and Li-6
. In addition, we calculate scattering lengths and exchange decay rate
s for cold collisions between identical lithium isotopes in different
hyperfine states. These quantities are used to examine the possibiliti
es of coexisting Li-7 Bose condensates and of evaporatively cooling co
existing Li-6 subsystems.