  We investigate dissociative single and double ionization of HeH+ induced by
intense femtosecond laser pulses. By employing a semi-classical model with
nuclear trajectories moving on field-dressed surfaces and ionization events
treated as stochastical jumps, we identify a strong-field mechanism wherein the
molecules dynamically align along the laser polarization axis and stretch
towards a critical internuclear distance before getting dissociative ionized.
As the tunnel-ionization rate is greater for larger internuclear distance and
for aligned samples, ionization is enhanced. The strong dynamical rotation is
traced back to a maximum in the parallel component of the
internuclear-distance-dependent polarizability tensor. Qualitative agreement
with our experimental observations is found. Finally the criteria for observing
the isotope effect for the ion angular distribution is discussed.
