  $K^-$ atomic data are used to test several models of the $K^-$ nucleus
interaction. The t($\rho$)$\rho$ optical potential, due to coupled channel
models incorporating the $\Lambda$(1405) dynamics, fails to reproduce these
data. A standard relativistic mean field (RMF) potential, disregarding the
$\Lambda$(1405) dynamics at low densities, also fails. The only successful
model is a hybrid of a theoretically motivated RMF approach in the nuclear
interior and a completely phenomenological density dependent potential, which
respects the low density theorem in the nuclear surface region. This best-fit
$K^-$ optical potential is found to be strongly attractive, with a depth of 180
\pm 20 MeV at the nuclear interior, in agreement with previous phenomenological
analyses.
