  We report on strong field ionization of S- and R-propylene oxide in
circularly polarized two-color laser fields. We find that the relative helicity
of the two single color laser fields affects the photoelectron circular
dichroism (PECD). Further, we observe that PECD is modulated as a function of
the sub-cycle release time of the electron. Our experimental observations are
successfully described by a heuristic model based on electrons in chiral
initial states, which are selectively liberated by the laser field and, after
tunneling, interact with an achiral Coulomb potential.
