The optical potential and observables for proton-Li-9,Li-11 elastic sc
attering are calculated microscopically using the single scattering ap
proximation to the Kerman-McManus-Thaler multiple scattering expansion
. The importance of the central and spin-orbit terms of the optical po
tential, and of the core and halo nucleon contributions, is clarified
in terms of the momentum space behaviors of the nucleon-nucleon amplit
udes and relevant density distributions. Calculations for the Li-9 and
Li-11 systems at 60 and 62 MeV/nucleon, respectively, are compared wi
th the available experimental data and with calculations and data for
the proton-He-8 system at similar energy. Three-body models of Li-11 a
re used. The effects of the halo distribution in Li-11 are clearly man
ifest in the elastic cross section but there are small differences bet
ween observables for structure models with realistic two-neutron asymp
totic behaviors. Calculations suggest that the Li-9 core structure is
not realistically described by simple models.