  Chirality is ubiquitous in nature and fundamental in science, from particle
physics to metamaterials.The most established technique of chiral
discrimination - photoabsorption circular dichroism - relies on the magnetic
properties of a chiral medium and yields an extremely weak chiral response. We
propose and demonstrate a new, orders of magnitude more sensitive type of
circular dichroism in neutral molecules: photoexitation circular dichroism. It
does not rely on weak magnetic effects, but takes advantage of the coherent
helical motion of bound electrons excited by ultrashort circularly polarized
light. It results in an ultrafast chiral response and the efficient excitation
of a macroscopic chiral density in an initially isotropic ensemble of randomly
oriented chiral molecules. We probe this excitation without the aid of further
chiral interactions using linearly polarized laser pulses. Our time-resolved
study of vibronic chiral dynamics opens a way to the efficient initiation,
control and monitoring of chiral chemical change in neutral molecules at the
level of electrons.
