  A Multi-Channel Algebraic Scattering (MCAS) approach has been used to analyze
the spectra of two hyper-nuclear systems, Lambda-9Be and Lambda-13C. The
splitting of the two odd-parity excited levels (1/2^- and 3/2^-) at 11 MeV
excitation in Lambda-13C is driven mainly by the weak Lambda-nucleus spin-orbit
force, but the splittings of the 3/2^+ and 5/2^+ levels in both Lambda-9Be and
Lambda-13C have a different origin. These cases appear to be dominated by
coupling to the collective 2+ states of the core nuclei. Using simple
phenomenological potentials as input to the MCAS method, the observed splitting
and level ordering in Lambda-9Be is reproduced with the addition of a weak
spin-spin interaction acting between the hyperon and the spin of the excited
target. With no such spin-spin interaction, the level ordering in Lambda-9Be is
inverted with respect to that currently observed. In both hyper-nuclei, our
calculations suggest that there are additional low-lying resonant states in the
Lambda-nucleus continua.
