  Coherence among rotational ion channels during photoionization is exploited
to control the anisotropy of the resulting photoelectron angular distributions
at specific photoelectron energies. The strategy refers to a robust and single
parameter control using two ultra-short light pulses delayed in time. The first
pulse prepares a superposition of a few ion rotational states, whereas the
second pulse serves as a probe that gives access to a control of the molecular
asymmetry parameter $\beta$ for individual rotational channels. This is
achieved by tuning the time delay between the pulses leading to channel
interferences that can be turned from constructive to destructive. The
illustrative example is the ionization of the $E(1\Sigma_{g}^{+})$ state of
Li$_{2}$. Quantum wave packet evolutions are conducted including both
electronic and nuclear degrees of freedom to reach angle-resolved photoelectron
spectra. A simple interference model based on coherent phase accumulation
during the field-free dynamics between the two pulses is precisely exploited to
control the photoelectron angular distributions from almost isotropic, to
marked anisotropic.
