  We examine transient circular dichroism spectroscopy (TRCD) as a technique to
investigate signatures of exciton coherence dynamics under the influence of
structured vibrational environments. We consider a pump-probe configuration
with a linearly polarized pump and a circularly polarized probe, with a
variable angle $\theta$ between the two directions of propagation. In our
theoretical formalism the signal is decomposed in chiral and achiral doorway
and window functions. Using this formalism, we show that the chiral doorway
component, which beats during the population time, can be isolated by comparing
signals with different values of $\theta$. As in the majority of time-resolved
pump-probe spectroscopy, the overall TRCD response shows signatures of both
excited and ground state dynamics. However, we demonstrate that the chiral
doorway function has only a weak ground state contribution, which can generally
be neglected if an impulsive pump pulse is used. These findings suggest that
the pump-probe configuration of optical TRCD in the impulsive limit has the
potential to unambiguously probe quantum coherence beating in the excited
state. We present numerical results for theoretical signals in an example dimer
system.
