  We analyze theoretically the interplay between the torsional and the
rotational motion of an aligned biphenyl-like molecule. To do so, we consider a
transition between two electronic states with different internal torsional
potentials, induced by means of a resonant laser pulse. The change in the
internal torsional potential provokes the motion of the torsional wavepacket in
the excited electronic state, modifying the structure of the molecule, and
hence, its inertia tensor. We find that this process has a strong impact on the
rotational wave function, displaying different behavior depending on the
electronic states involved and their associated torsional potentials. We
describe the dynamics of the system by considering the degree of alignment and
the expectations values of the angular momentum operators for the overall
rotation of the molecule.

Chemical Physics;Quantum Physics