  Accurate knowledge of absorption coefficient of a sample is a prerequisite
for measuring the third order optical nonlinearity of materials, which could
become a serious limitation for unknown samples. We introduce a new method,
which measures both the absorption coefficient and the third order optical
nonlinearity of materials with high sensitivity in a single experimental setup.
We use a dual-beam pump-probe experiment under different conditions to achieve
this goal. We also demonstrate a counterintuitive coupling of the
non-interacting probe-beam with the pump-beam in pump-probe z-scan experiment.
