On the dissipation of the rotation energy of dust grains in interstellar
  magnetic fields
  A new mechanism is described, analyzed and visualized, for the dissipation of
suprathermal rotation energy of molecules in magnetic fields, a necessary
condition for their alignment. It relies upon the Lorentz force perturbing the
motion of every atom of the structure, as each is known to carry its own net
electric charge because of spatial fluctuations in electron density. If the
molecule is large enough that the frequency of its lowest-frequency phonon lies
near or below the rotation frequency, then the rotation couples with the
molecular normal modes and energy flows from the former to the latter. The rate
of this exchange is very fast, and the vibrational energy is radiated away in
the IR at a still faster rate, which completes the removal of rotation energy.
The energy decay rate scales like the field intensity, the initial angular
velocity, the number of atoms in the grain and the inverse of the moment of
inertia. It does not depend on the susceptibility. Here, the focus is on
carbon-rich molecules which are diamagnetic. The same process must occur if the
molecule is paramagnetic or bathes in an electric field instead.
  A semi-empirical method of chemical modeling was used extensively to
illustrate and quantify these concepts as applied to a hydrocarbon molecule.
The motion of a rotating molecule in a field was monitored in time so as to
reveal the energy transfer and visualize the evolution of its orientation
towards the stable configuration.
